Article

Role of bacteria and bacterial exopolymer in the attachment of Achnanthes longipes (Bacillariophyceae)

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Abstract

The attachment of diatoms to surfaces is an important and poorly understood step in the development of biofouling communities. Experiments were performed in vitro on a common fouling diatom (Achnanthes longipes) to determine the influence of the base material and bacterial conditioning on diatom attachment. The first series of experiments compared attachment of A. longipes to four different base materials, and the influence of a bacterial film on attachment to these materials. A. longipes preferentially attached to polystyrene, a hydrophobic surface, but was inhibited by the presence of a bacterial biofilm. On other surfaces, bacteria either facilitated or had no effect on algal attachment. The second series of experiments found no difference in the attachment of A. longipes to a surface covered with bacterial exopolymer compared to a surface with a film of living bacteria. Attachment of A. longipes was found to vary depending on the conditions under which the bacterial film developed and the species of bacteria within the film. These results help to illustrate the complexity of the relationship between surfaces and attaching organisms and show that bacteria may either facilitate, have no effect or inhibit attachment by diatoms. The mechanisms underlying these patterns require further investigation.

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... Former studies showed that surface materials may influence diatom attachment and biofilm formation (Gawne et al. 1998, Mieszkin et al. 2012. Polystyrene for example, represents a hydrophobic surface and was found to be preferred out of four different materials for attachment of the diatom Achnanthes longipes (Gawne et al. 1998). ...
... Former studies showed that surface materials may influence diatom attachment and biofilm formation (Gawne et al. 1998, Mieszkin et al. 2012. Polystyrene for example, represents a hydrophobic surface and was found to be preferred out of four different materials for attachment of the diatom Achnanthes longipes (Gawne et al. 1998). In our study, axenic A. minutissimum did not attach to polystyrene of the FIG. 6. ...
... DIATOM/BACTERIA INTERACTIONS well plates and hence attachment only depends on Bacteroidetes strain 32 or its spent medium. Gawne et al. (1998) and Mieszkin et al. (2012) further showed that bacterial biofilms on surfaces may influence attachment of diatoms in a positive or negative way and often precedes biofilm formation of diatoms. As biofilm of A. minutissimum can be also induced by the sterile supernatant of the bacterium, preceding biofilm formation of the bacterium as a sort of base layer is obviously not the only reason for attachment of the alga. ...
Article
Photoautotrophic biofilms play an important role in various aquatic habitats and are composed of prokaryotic and/or eukaryotic organisms embedded in extracellular polymeric substances (EPS). We have isolated diatoms as well as bacteria from freshwater biofilms to study organismal interactions between representative isolates. We found that bacteria have a strong impact on the biofilm formation of the pennate diatom Achnanthidium minutissimum. This alga produces extracellular capsules of insoluble EPS, mostly carbohydrates (CHO), only in the presence of bacteria (xenic culture). The EPS themselves also have a strong impact on the aggregation and attachment of the algae. In the absence of bacteria (axenic culture), A. minutissimum did not form capsules and the cells grew completely suspended. Fractionation and quantification of CHO revealed that the diatom in axenic culture produces large amounts of soluble CHO, whereas in the xenic culture mainly insoluble CHO were detected. For investigation of biofilm formation by A. minutissimum, a bioassay was established using a diatom satellite Bacteroidetes bacterium that had been shown to induce capsule formation of A. minutissimum. Interestingly, capsule and biofilm induction can be achieved by addition of bacterial spent medium, indicating that soluble hydrophobic molecules produced by the bacterium may mediate the diatom/bacteria interaction. With the designed bioassay, a reliable tool is now available to study the chemical interactions between diatoms and bacteria with consequences for biofilm formation.
... Former studies showed that surface materials may influence diatom attachment and biofilm formation (Gawne et al. 1998, Mieszkin et al. 2012. Polystyrene for example, represents a hydrophobic surface and was found to be preferred out of four different materials for attachment of the diatom Achnanthes longipes (Gawne et al. 1998). ...
... Former studies showed that surface materials may influence diatom attachment and biofilm formation (Gawne et al. 1998, Mieszkin et al. 2012. Polystyrene for example, represents a hydrophobic surface and was found to be preferred out of four different materials for attachment of the diatom Achnanthes longipes (Gawne et al. 1998). In our study, axenic A. mintttissimum did not attach to polystyrene of the well plates and hence attachment only depends on Bacteroidetes strain 32 or its spent medium. ...
... In our study, axenic A. mintttissimum did not attach to polystyrene of the well plates and hence attachment only depends on Bacteroidetes strain 32 or its spent medium. Gawne et al. (1998) and Mieszkin et al. (2012) further showed that bacterial biofilms on surfaces may influence attachment of diatoms in a positive or negative way and often precedes biofilm formation of diatoms. As biofilm of A. minutissimum can be also induced by the sterile supernatant of the bacterium, preceding biofilm formation of the bacterium as a sort of base layer is obviously not the only reason for attachment of the alga. ...
Article
Photoautotrophic biofilms play an important role in various aquatic habitats and are composed of prokaryotic and/or eukaryotic organisms embedded in extracellular polymeric substances (EPS). We have isolated diatoms as well as bacteria from freshwater biofilms in order to study organismal interactions between representative isolates. We found that bacteria have a strong impact on the biofilm formation of the pennate diatom Achnanthidium minutissimum (Kützing) Czarnecki. This alga produces extracellular capsules of insoluble EPS, mostly carbohydrates, only in the presence of bacteria (xenic culture). The EPS itself also have a strong impact on the aggregation and attachment of the algae. In the absence of bacteria (axenic culture), A. minutissimum did not form capsules and the cells grew completely suspended. Fractionation and quantification of carbohydrates revealed that the diatom in axenic culture produces large amounts of soluble carbohydrates, whereas in the xenic culture mainly insoluble carbohydrates were detected. For investigation of biofilm formation by A. minutissimum, a bioassay was established using a diatom satellite Bacteroidetes bacterium which had been shown to induce capsule formation of A. minutissimum. Interestingly, capsule and biofilm induction can be achieved by addition of bacterial spent medium, indicating that soluble hydrophobic molecules produced by the bacterium may mediate the diatom/bacteria interaction. With the designed bioassay a reliable tool is now available to study the chemical interactions between diatoms and bacteria with consequences for biofilm formation.This article is protected by copyright. All rights reserved.
... Different microor- ganisms have contrasting effects on the settlement of other fouling organisms and the nature of the underlying surface also plays an impor- tant role. For instance, the diatom (microscopic alga) Achnanthes longipes is a common fouler in shallow water, attaches preferentially to hydro- phobic surfaces but is inhibited by live biofilms and bacterial extracellu- lar polymeric substances (EPS) ( Gawne et al., 1998). However, the presence of EPS can modify the surface of the substrate (in terms of surface energy and topography) in favour of A. longipes settlement ( Gawne et al., 1998). ...
... For instance, the diatom (microscopic alga) Achnanthes longipes is a common fouler in shallow water, attaches preferentially to hydro- phobic surfaces but is inhibited by live biofilms and bacterial extracellu- lar polymeric substances (EPS) ( Gawne et al., 1998). However, the presence of EPS can modify the surface of the substrate (in terms of surface energy and topography) in favour of A. longipes settlement ( Gawne et al., 1998). Where the substrate surface was initially hydro- phobic, the development of a bacterial biofilm increased attachment of A. longipes but where the substrate was initially hydrophilic, attachment was not increased. ...
... Where the substrate surface was initially hydro- phobic, the development of a bacterial biofilm increased attachment of A. longipes but where the substrate was initially hydrophilic, attachment was not increased. Various biofilm-forming bacteria produced biofilm surfaces with different propensities for subsequent attachment of A. longipes ( Gawne et al., 1998). The properties of the surface, pre- existing biofilms and the presence of diffusible molecular signals are also important in determining the propensity of other macrofouling organisms, including crustacea and molluscs, to settle Callow, 2000, 2002;Khandeparker and Kumar, 2011). ...
Article
Following the ban in 2003 on the use of tributyl-tin compounds in antifouling coatings, the search for an environmentally-friendly alternative has accelerated. Biocidal TBT alternatives, such as Diuron and Irgarol 1051®(,)(⁎) have proved to be environmentally damaging to marine organisms. The issue regarding the use of biocides is that concerning the half-life of the compounds which allow a perpetuation of the toxic effects into the marine food chain, and initiates changes in the early stages of the organisms' life-cycle. In addition, the break-down of biocides can result in metabolites with greater toxicity and longevity than the parent compound. Functionalized coatings have been designed to repel the settlement and permanent attachment of fouling organisms via modification of either or both surface topography and surface chemistry, or by interfering with the natural mechanisms via which fouling organisms settle upon and adhere to surfaces. A large number of technologies are being developed toward producing new coatings that will be able to resist biofouling over a period of years and thus truly replace biocides as antifouling systems. In addition urgent research is directed towards the exploitation of mechanisms used by living organisms designed to repel the settlement of fouling organisms. These biomimetic strategies include the production of antifouling enzymes and novel surface topography that is incompatible with permanent attachment, for example, by mimicking the microstructure of shark skin. Other research seeks to exploit chemical signals and antimicrobial agents produced by diverse living organisms in the environment to prevent settlement and growth of fouling organisms on vulnerable surfaces. Novel polymer-based technologies technology may prevent fouling by means of unfavourable surface chemical and physical properties or by concentrating antifouling compounds around surfaces.
... The adhesion strength of diatoms may be reduced (Wigglesworth-Cooksey & Cooksey, 2005), enhanced (Grossart, 1999), or even fluctuate depending on the cultivation parameters (Gawne et al., 1998). There are indications that extracellular bacterial factors are involved in these effects (Baker & Herson, 1978). ...
... Diatom attachment is thought to be an active process that requires glycoproteins and metabolic energy (Dugdale et al., 2006;Chiovitti et al., 2003, Cooksey & Wigglesworth-Cooksey, 1995. In mixed biofilm communities diatom EPS might interact specifically with bacterial EPS by forming colloidal structures (Gawne at al., 1998). ...
... The observed effects were often ambiguous. Growth of diatoms can be enhanced or can be suppressed by bacteria (Grossart & Simon, 2007;Grossart et al., 2006;Baker & Herson, 1978); also the strength of adhesion to a substratum can be increased (Grossart, 1999) or reduced (Wigglesworth- Cooksey & Cooksey, 2005) or even can fluctuate, depending on the growth conditions of the associated bacteria (Gawne et al., 1998). This is accompanied by changes within the diatom EPS (Grossart, 1999), as indicated by lectin labeling (Wigglesworth-Cooksey & Cooksey, 2005). ...
Article
In this study we developed methods to purify diatoms from associated bacteria. Therefore most diatoms could be purified by short term harsh antibiotics treatment followed by single cell care. Diatoms that are difficult to purify could be made axenic via an intermediate defined co-culture with Escherichia coli. Phylogenetic analysis via 16S rRNA gene profiling of diatom associated bacteria indicated that Alphaproteobacteria and Bacteroidetes have adapted to the micro environment diatom biofilm. Defined co-cultures of diatoms and bacteria support this hypothesis by indicating that different bacteria utilize different fractions of secreted diatom carbohydrates. Bacteria were found to influence diatom growth strongly, either direct or by constitutively released soluble substances. We found concentrations of dissolved free amino acids (DFAA), analyzed by HPLC via ortho-phthaldialdehyde derivatization, to correlate with diatom growth when influenced by bacteria, and thus postulate that DFAA may be one class of such substances, regulating growth rate and growth density of diatoms. Further bacteria have a strong influence on the secretion of extracellular polymeric substances (EPS) by the diatoms. Investigating diatom carbohydrates by HPAE-PAD and spectrophotometric assays revealed that diatom carbohydrate secretion is influenced predominately quantitatively by bacteria. By quantifying diatom protein secretion and separating diatom proteins via SDS-PAGE we found diatom protein secretion to be influenced qualitatively and quantitatively by bacteria. The model organisms Phaeodactylum tricornutum and Escherichia coli were used to identify via Maldi-tof mass spectrometry peptide mass fingerprinting extracellular bacteria and diatom proteins that are induced during biofilm formation as an interaction of these organisms. These proteins could be related to different functions that are thought to play an important role during this interaction. Im Rahmen dieser Arbeit wurden systematisch Methoden entwickelt, um Diatomeen von assoziierten Bakterien zu reinigen. Die meisten Kieselalgen konnten dabei durch kurzzeitige Behandlung mit hochkonzentrierten Antibiotika-Kombinationen von Bakterien befreit werden, wobei in schwierigen Fällen eine intermediäre Escherichia coli Co-Kultur hilfreich war. Phylogenetische Studien indizieren, dass Alphaproteobakteria und Bacteroidetes sich an den Mikrolebensraum Kieselalgenbiofilm anpassen konnten. Definierte Co-Kulturen aus Diatomeen und Bakterien unterstützen diese Hypothese, da verschiedene dieser Bakterien unterschiedliche Fraktionen der von den Kieselalgen sekretierten Kohlenhydrate verstoffwechselten. Ferner konnte gezeigt werden, dass Bakterien das Wachstum der Diatomeen stark beeinflussen, entweder direkt oder über konstitutiv freigesetzte lösliche Faktoren. Mittels HPLC-Quantifizierung über Ortho-Phthaldialdehyd Derivatisierung freier löslicher Aminosäuren (DFAA) fanden wir Korrelationen zwischen DFAA Konzentrationen und Diatomeenwachstum unter bakteriellem Einfluss. DFAA könnten daher eine Substanzklasse darstellen, die einen regulativen Einfluss auf Kieselalgen ausübt und Wachstumsgeschwindigkeit und Wachstumsdichte der Diatomeen steuert. Weiterhin üben Bakterien einen starken Einfluss auf die Sekretion extrazellulärer polymerer Substanzen durch die Kieselalgen aus: mittels spektrophotometrischer Quantifizierung und HPAE-PAD fanden wir Diatomeenkohlenhydratsekretion vor allem quantitativ beeinflusst, Proteinsekretion aber quantitativ wie qualitativ. Die Modellorganismen Phaeodactylum tricornutum und Escherichia coli wurden verwendet um mittels Maldi-tof Massenspektrometrie-Peptidmassenabgleich Proteine zu identifizieren, welche bei der Biofilmbildung als Funktion der Wechselwirkung zwischen den Organismen induziert werden. Diese Proteine konnten umfassenden Funktionen zugeordnet werden und indizieren dadurch wichtige Vorgänge während der Biofilmbildung durch Kieselalgen und Bakterien.
... Meanwhile, it is accepted that diatoms are the first eukaryotic organisms to colonize on any new surface submerged in the water. However, the presence of bacteria on surfaces can accelerate algal attachment (Gawne et al., 1998) or may have either inhibitory or stimulatory effect on algal growth depending on the taxa involved (Cole, 1982;Hoagland et al., 1993). This biofilms formation is affected by surface topology, surface charges, the presence of organic films, temperature, availability of nutrients and associated species (Gawne et al., 1998). ...
... However, the presence of bacteria on surfaces can accelerate algal attachment (Gawne et al., 1998) or may have either inhibitory or stimulatory effect on algal growth depending on the taxa involved (Cole, 1982;Hoagland et al., 1993). This biofilms formation is affected by surface topology, surface charges, the presence of organic films, temperature, availability of nutrients and associated species (Gawne et al., 1998). ...
... As bacteria are also primary colonizers, specific interaction might be present to facilitate or inhibit diatom attachment. Gawne et al. (1998) showed the attachment of Achnanthes longipes on Chapter 1: General introduction _____________________________________________________________________ hydrophobic surfaces like polystyrene is inhibited by bacterial biofilms whereas on other surfaces, bacterial biofilms either facilitate or have no effect on diatom attachment. Under axenic condition diatoms showed evenly distributed growth whereas after addition of bacteria diatoms showed clump formation and eventual death of diatoms was observed (Wigglesworth- . ...
Article
Full-text available
In this work, various aspects of diatom communities from epilithic biofilms of Lake Constance were studied. The diatom and bacterial community structure and extracellular polymeric substances (EPS) were studied at five nearby locations and at four different depths from epilithic biofilms. This study revealed a high species richness of diatoms and a dominance of β-proteobacteria, Cytophaga / Flavobacteria / Bacteroides (CFB) group and high GC containing gram-positive bacteria. Higher amount of EPS was observed in the samples from lower depth. Seasonal fluctuations of the diatom community and concentrations of soluble (SE) and bound EPS (BE) were studied from epilithic biofilms collected during June 2004-June 2005. The higher diversity and also higher EPS content was observed in biofilms from April 2005. We tried to cultivate dominant as well as rarely found diatom species from the biofilms and identified then by classical methods based on morphological characters. More than 100 isolates were cultivated belonging to 20 different genera and 44 species. The 18S rDNA region was sequenced from 55 diatom isolates and phylogenetic trees were constructed. They revealed a clear separation within raphid and araphid diatoms. Axenic diatoms were grown for 28 days under identical growth conditions (temperature, light intensity, nutrients) and their growth behavior, patterns of EPS secretion and the corresponding monosaccharide profiles were studied. As in this experiment we observed that a major portion of BE was remained un-extractable, various published methods were tried and finally an optimized protocol was used for the fractionation of all EPS secreted by diatoms from various genera. FITC labeled-lectins, DAPI and DTAF were used for localization of various EPS structures such as tubes, stalks, capsules and pads. As diatoms and bacteria are the dominant members in the biofilms, uni-algal diatom cultures were studied for the associated bacteria using 16S rDNA clone library approach. The spent medium from diatoms was inoculated with an epilithic bacterial community in a dilution series to explore the utilization of EPS, a natural substrate, for the growth of bacteria. One of the dominant bacterial strain was isolated found to represent a new taxon. Im Rahmen dieser Arbeit wurden Kieselalgengesellschaften der epilithischen Biofilme des Bodensees untersucht. Die Lebensgemeinschaften von Diatomeen und Bakterien und deren extrazelluläre lösliche Substanzen (EPS) wurden an fünf verschiedenen benachbarten Probenameorten für vier verschiedene Tiefen charakterisiert. Eine große Artenvielfalt bezüglich der Diatomeen wurde vorgefunden. Die dominanten Bakteriengruppen in diesen Proben waren β-Proteo-, CFB- und grampositive Bakterien, letztere mit hohem GC-Gehalt. In Proben aus geringeren Tiefen wurden höhere EPS-Konzentrationen vorgefunden, ferner annuale Fluktuationen bezüglich löslicher und gebundener EPS von Juni 2004 bis Juni 2005. Es wurde versucht häufig wie auch selten vorgefundene Kieselalgen zu kultivieren. Die Klassifizierung der Arten geschah anhand morphologischer Merkmale. Es wurden über 100 Stämme isoliert, die 44 Arten und 20 Genera zugeordnet werden konnten. Von 55 Isolaten wurde die 18S rDNS sequenziert und phylogenetische Stammbäume erstellt. Dabei konnten raphide Diatomeen klar von araphiden abgegrenzt werden. Bei identischen Wachstumsbedingungen (Temperatur, Lichtstärke, Nährstoffe) wurden die EPS Sekretion hinsichtlich der Monosaccharid-Zusammensetzung untersucht. Das Verfahren wurde anhand verschiedener, in der Literatur vorhandener Methoden für die kultivierten Diatomeen optimiert. FITC-gekoppelte Lektine, DAPI und DTAF wurden zur Lokalisation verschiedener EPS-Strukturen wie Schläuche, Stiele, Kapseln und Pads verwendet. Da Diatomeen und Bakterien Biofilme dominieren wurden kontaminierte Kulturen bezüglich der bakteriellen Artenzusammensetzung mittels 16S rDNS Bibliotheken untersucht. Kulturüberstand von Diatomeen wurde mit Bodensee-Bakteriengemischen über Verdünnungsreihen inokuliert um den EPS-Abbau durch letztere zu untersuchen. Eine der dominanten Bakterienarten wurde dabei isoliert und repräsentiert ein neues Taxon.
... Benjamin Gawne et al. (1998) studied the role of bacteria and bacterial exopolymer in attaching Achnanthes longipes (Bacillariophyceae) to any surface and illustrated this complex relationship of attachment of attached organisms to a surface. The role of bacteria was found to either facilitate, have no effect, or inhibit the attachment of diatoms to different surfaces. ...
... The role of bacteria was found to either facilitate, have no effect, or inhibit the attachment of diatoms to different surfaces. The mechanisms underlying this relationship and patterns were not thoroughly studied and required further investigation [74]. ...
Article
Humans have used algae for hundreds of years to make various products viz. agar, fertilizer, food, and pigments. Algae are also used in bioremediation to clean up polluted water and as essential laboratory tools in genomics, proteomics, and other research applications such as environmental warnings. Several special features of algae, including the oxygenic photosynthesis, higher yield in biomass, growth on the non-arable lands, their survival in a wide range of water supplies (contaminated or filtered waters), the production of necessary byproducts and biofuels, the enhancement of soil productivity, and the greenhouse gas emissions, etc. altogether rendered them as vital bio-resources in the sustainable development. Algae and bacteria have been assumed to coexist from the early stages of the development of the earth, and a wide variety of interactions were observed between them which have influenced the ecosystems ranging from the oceans to the lichens. Research has shown that bacteria and algae interact synergistically, especially roseobacter-algae interactions being the most common. These interactions are common to all ecosystems and characterize their primary efficiency. The commercialization of algae for industrial purposes, an important field, is also influenced by this interaction which frequently results in bacterial infections among the consumers. However, the recent findings have revealed that the bacteria improve algal growth and support flocculation which are very crucial in algal biotechnology. Some of the most exciting advancements in the area of algal biotic interactions and potential difficulties were reviewed in this article. Information gleaned in this study would provide a firm foundation for launching more contemporaneous research efforts in understanding and utilizing the algal species in biotechnology industries and medical sectors.
... However, it must be kept in mind that the latter study has been conducted in the laboratory under controlled conditions with absence or presence of bacteria. According to Wahl [63], in natural systems, the pattern of bacteria colonizing surfaces before diatoms is either due to their higher relative abundance in the immigrant pool [64] or because they facilitate diatom attachment [65]. Furthermore, it has been reported that the role of bacteria is variable wherein bacteria may facilitate algal attachment if the base material is hydrophilic or has no effect and even inhibit algal attachment if the base material is hydrophobic [64]. ...
... According to Wahl [63], in natural systems, the pattern of bacteria colonizing surfaces before diatoms is either due to their higher relative abundance in the immigrant pool [64] or because they facilitate diatom attachment [65]. Furthermore, it has been reported that the role of bacteria is variable wherein bacteria may facilitate algal attachment if the base material is hydrophilic or has no effect and even inhibit algal attachment if the base material is hydrophobic [64]. Therefore, the type of surface along with the type of bacterial community will influence the bacteriadiatom interactions in the natural environment which will in turn influence the process of ennoblement. ...
Article
Full-text available
This paper reports the development of biofilms on stainless steels (SS) upon exposure in a natural freshwater ecosystem for about six months and focuses on the composition of diatom populations. By using environmental scanning electron microscopy (ESEM) technique, we provide a detailed description regarding diatom identification at species level as well as their main characteristics, including type, morphology, ability to form colony, and motility. Results reveal the presence of both prostrate (initial colonizers) and stalked (late colonizers) forms. Pennate diatoms, Cocconeis placentula and Amphora coffeaeformis, and a centric diatom, Melosira varians, are shown to be the abundant forms regardless of the SS type. Pennate diatoms dominate the community and are directly attached to the substratum, whereas the centric form is entangled in the biofilm matrix in a significant number. The dominance of adnate forms suggests that these cells are sturdy and successfully maintaining their population. In situ monitoring of the electrochemical response of immersed materials showed ennoblement of the open circuit potential, which seems to be due to the biogenic production of H2O2, detected in a significant amount within the biofilms. The substantial enrichment of biofilms with diatoms potentially suggests the implication of these microorganisms in the process of ennoblement. A mechanism is proposed in this paper describing the possible interactions of diatom community with SS in the studied ecosystem.
... Assays carried out using surfaces of different wettability have provided contrasting effects. For example, single-species biofilms formed from Pseudomonas atlantica reduced the settlement of the diatom Achnanthes longipes on polystyrene and enhanced it on glass while no effect was observed on silicone coatings (Gawne et al. 1998). In the same way, biofilms of C. marina enhanced the settlement of spores of U. linza on glass and on an amphiphilic fouling-release coating (Intersleek ® 900 (IS900)) while settlement was reduced on hydrophobic coatings (Intersleek ® 700 (IS700) and an unpigmented poly(dimethylsiloxane) (PDMS) elastomer) (Mieszkin et al. 2012). ...
... Thus, there is no certainty that interactions between microbial biofilms and algae occur in a similar way in the natural marine environment, where a consortium of bacteria and other biofilm organisms (protozoa, fungi and unicellular algae) is also present. Moreover, the complexity of interpreting data is further increased by considerations such as the influence of the physicochemical properties of coating/surface and the presence of molecular conditioning films (Gawne et al. 1998;Mieszkin et al. 2012;Thomé et al. 2012). ...
Article
Natural and artificial substrata immersed in the marine environment are typically colonized by microorganisms, which may moderate the settlement/recruitment of algal spores and invertebrate larvae of macrofouling organisms. This mini-review summarizes the major interactions occurring between microbial biofilms and marine fouling algae, including their effects on the settlement, growth and morphology of the adult plants. The roles of chemical compounds that are produced by both bacteria and algae and which drive the interactions are reviewed. The possibility of using such bioactive compounds to control macrofouling will be discussed.
... Co-cultivation experiments using diatoms and bacteria have revealed various other effects: bacterial growth and DNA synthesis may be stimulated (Murray et al., 1986) and in parallel diatom growth may be suppressed or enhanced (Ukeles and Bishop, 1975;Baker and Herson, 1978;Fukami et al., 1997;Hirayama and Hirayama, 1997). The adhesion strength of diatoms may be reduced (Wigglesworth-Cooksey and Cooksey, 2005), enhanced (Grossart, 1999) or even fluctuate depending on the cultivation parameters and the presence of microbial communities ( Gawne et al., 1998). Also the involvement of extracellular bacterial factors has been proposed (Baker and Herson, 1978), accompanied by a qualitative change in EPS composition (Grossart, 1999). ...
... In earlier studies, via monomer mapping of extracellular diatom carbohydrates, we showed that in epilithic diatom/bacteria co-cultures, diatoms clearly produce most of the carbohydrates whereas the carbohydrate fraction secreted by bacteria is negligible (Bruckner et al., 2008). In accordance with earlier observations, we also found ambiguous effects of bacteria on the quantity of carbohydrate secretion by epilithic freshwater diatoms ( Gawne et al., 1998;Grossart, 1999;Wigglesworth-Cooksey and Cooksey, 2005). Additionally, we identified several E. coli proteins that are thought to be involved in degradation/modification of such carbohydrates and its subsequent utilization as a substrate. ...
Article
Phototrophic epilithic biofilms harbour a distinct assemblage of heterotrophic bacteria, cyanobacteria and photoautotrophic algae. Secretion of extracellular polymeric substances (EPS) by these organisms and the physicochemical properties of the EPS are important factors for the development of the biofilms. We have isolated representative diatom and bacteria strains from epilithic biofilms of Lake Constance. By pairwise co-cultivating these strains we found that diatom growth and EPS secretion by diatoms may depend on the presence of individual bacteria. Similar results were obtained after addition of spent bacterial medium to diatom cultures, suggesting that soluble substances from bacteria have an impact on diatom physiology. While searching for putative bacterial signal substances, we found that concentrations of various dissolved free amino acids (DFAA) within the diatom cultures changed drastically during co-cultivation with bacteria. Further, the secretion of extracellular carbohydrates and proteins can be influenced by bacteria or their extracellular substances. We have performed mass spectrometric peptide mapping to identify proteins which are secreted when co-cultivating the diatom Phaeodactylum tricornutum Bohlin and Escherichia coli. The identified proteins are possibly involved in signalling, extracellular carbohydrate modification and uptake, protein and amino acid modification, and cell/cell aggregation of diatom and bacteria strains. Our data indicate that diatom-bacteria biofilms might be regulated by a complex network of chemical factors involving EPS, amino acid monomers and other substances. Thus interactions with bacteria can be considered as one of the main factors driving biofilm formation by benthic diatoms.
... These initial biofilm organisms are known to produce exopolymers that assist the process of adhesion and movement (Molino and Wetherbee, 2008). So, the observed pattern of biofilm community development in natural systems (bacteria preceding algae) is more likely to be a reflection of the average abundance and the availability of the different colonizing forms at the moment of immersion of a new substratum (Gawne et al., 1998;Wahl, 1989). In view of this, considering the cell size, cell availability and cell abundance, since picophytoplankton are next to bacteria, it was hypothesized that picophytoplankton are the first autotrophic colonizers in biofilms contributing significantly to the biofilm photosynthetic biomass in the initial stages thereby playing an important role in the biofilm food web dynamics and probably in the production of exopolymers similar to bacteria and diatoms (Patil and Anil, 2005c). ...
... Studies on community ecology of epiphytes and their relationships with the host and environment across spatio-temporal scales remain limited (Perkins et al., 2016). Moreover, in comparison with bacterial epiphytes or epibionts (Gawne et al., 1998;Mieszkin et al., 2013), epiphytic eukaryotic protists have been less studied. Given the economic value of seaweeds, understanding their associated species, especially the eukaryotic epiphytes, would contribute to addressing challenges posed by seaweed-microorganism associations. ...
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Epiphytic microalgae can significantly affect the host seaweed either by complementing, or competing for, resources. Here, epiphytic diatom and dinoflagellate species assemblages on the macroalgae Acanthophora spicifera, Hypnea pannosa and Gracilaria salicornia collected during the north-east (February), inter- (April) and south-west (June) monsoons in 2015 along the coast of Lucero, Pangasinan, North-western Philippines were examined and characterized. Results showed that diatom–dinoflagellate assemblages strongly clustered by season rather than by geographic location. Within season, a minor clustering by macroalgal forms, rather than host species identity, was also observed, which could be associated with the differences in the complexity and texture of the upright and prostrate seaweeds. Examination of the ‘thallisphere’ using confocal laser scanning microscopy further revealed the close proximity of some of the ‘resident’ epiphytic species to the cortical cells of the host, causing deformities and implying more complex interactions. Our results suggest that epiphytic community assemblages were influenced by both the environmental conditions associated with seasonal variation and the microhabitats in the surface of the different algal forms.
... Although we believe that relative contributions of different diatom growth forms (or ecological guilds) may provide valuable information about the host animal, adequate methods must be used to gather the necessary information, and correctly assign the diatoms to their ecological groups. It has been shown that, for example, diatom-associated bacteria may have a profound impact on diatom ecophysiology, including growth form and ability of diatom to attach to the substratum surface (Gawne et al. 1998). Further investigations are required to shed more light on the complex relationships between epizoic diatoms and their bacterial partners. ...
Article
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The current study investigated diatom communities on juvenile green turtles foraging in neritic habitats around five Iranian islands. The primary objectives were to (1) compare species composition, growth form structure, and abundance of diatom communities associated with sea turtles foraging within the restricted boundaries of local feeding pastures, and (2) assess the level of uniqueness of the epizoic diatom flora in comparison with biofilms growing on floating debris. All observations and diatom counts were performed using scanning electron microscopy. The effect of the sampling location was apparent among sea turtle samples and reflected in significantly different cell densities. Diatom abundances were significantly higher on sea turtles (758-1836 cells mm −2) than on floating debris samples (9-189 cells mm −2). Epizoic diatom communities were composed of 20 diatom taxa and dominated by erect forms belonging to the so-called 'marine gomphonemoids', Chelonicola and Poulinea, previously reported on sea turtles from other geographical regions. The diatom flora found on floating debris was composed of 21 taxa. Only four taxa, Amphora cf. bigibba, Cocconeis cf. neothumensis var. marina, Psammodictyon constrictum, and Tabularia affinis, were recorded from both sea turtles and floating debris samples, and none of these exceeded 4% of the average relative abundance on the sea turtle carapaces. The study reveals a clear substratum preference in sea turtle-associated diatoms, with no evidence for species turnover across the investigated region over different sampling seasons, thus confirming previous speculations that sea turtle diatom communities would show a high level of uniqueness and stability.
... La présence de bactéries peut accroitre ou inhiber la production d'EPS par les microalgues. Ces modifications dans la production des EPS peuvent ralentir la croissance des microalgues ou diminuer les forces d'adhésion vis-à-vis de la surface (Gawne et al., 1998 ;Grossart 1999 ;Grossart et al., 2006 ;Grossart & Simon., 2007). ...
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Le développement de salissures marines (ou biofouling) est à l’origine de nombreux problèmes économiques et écologiques. Ces salissures marines sont constituées de microorganismes (bactéries, microalgues…) formant le microfouling sur lequel va se développer le macrofouling constitué de macroorganismes tels que les algues, coquillages et éponges. La formation de ces salissures va induire un ralentissement des navires provoquant une surconsommation de carburant. De plus, l’utilisation de revêtements antisalissures ou peintures antifouling à base de métaux lourds et de biocides dans le passé a conduit à des problèmes environnementaux. L’objectif de la thèse est de rechercher une alternative aux composés actuellement utilisés (cuivre) en respectant le milieu marin. L’environnement est une source d’inspiration, une approche biomimétique pourrait être une stratégie de lutte efficace contre le biofouling. Dans une première partie, un criblage d’une centaine de composés est réalisé contre des souches bactériennes. Huit composés issus des deux familles : les batatasins et les hemibastadins sont étudiées en vue de comprendre leurs modes d’action. Parmi les composés sélectionnés, la famille des hemibastadins comprenant le DiBromoHemiBastadin-1 (DBHB) a montré des propriétés antifouling prometteuses. En effet, cette molécule est capable d’inhiber 50 % la formation du biofilm avec une IC50= 6,44 µg/mL pour la bactérie Pseudomonas aeruginosa PAO1 et une IC50 = 12,8 µg/mL pour la bactérie marine Paracoccus sp. 4M6. Afin de comprendre le mode d’action de cette molécule, son impact sur la communication bactérienne, le quorum sensing est étudié et le composé DBHB est capable de l’inhiber. Dans une seconde partie, un autre groupe d’organismes participant au microfouling est étudié : les microalgues. Afin d’évaluer l’impact de composés de la famille des hemibastadins et notamment du DBHB, l’adhésion et la formation de biofilm de microalgues sont étudiées. Le DBHB montre des inhibitions de l’adhésion et de la formation du biofilm uniquement envers la diatomée Cylindrotheca closterium. Une dernière partie, s’est intéressée à l’évaluation de revêtements contenant six composés de la famille des batatasins et des hemibastadins sur le microfouling naturel. Une méthode d’immersion de revêtements en conditions contrôlées (photobioréacteur) est mise au point afin de pallier aux contraintes environnementales. L’ensemble de cette étude a permis de mettre en évidence les propriétés antifouling du DBHB et de caractériser son mode d’action. Ce composé offre d’intéressantes voies d’étude dans la lutte contre le biofouling. De plus, l’approfondissement des connaissances sur les procédés d’adhésion et de formation de biofilm de microalgues permet de définir de nouvelles stratégies de lutte.
... As the earliest colonizers of the substrate, it has been long proposed that bacteria colonization may facilitate colonization of microbial eukaryotes (Zobell & Allen, 1935), by creating surface heterogeneity with the initial stochastic colonization of bacteria on a newly submerged substrate. Indeed, bacteria and their EPS have been shown to be able to affect colonization of diatom, in both positive and negative ways (Gawne et al., 1998). On the other hand, colonization of the microbial eukaryotes could also change the heterogeneity of micro-environment. ...
Thesis
Biofouling by barnacles is a problem commonly encountered in mangrove replanting projects. This study examined the effect of biofilm and snail grazing on settlement of cyprids and proposed solution to control biofouling. An effective identification tool for barnacle cyprids was first built to facilitate the study as the barnacle cyprids are very difficult to identify. Several species of wild-caught barnacle cyprids from Matang Mangrove Forest Reserve waters were studied. The cyprids were identified through DNA barcoding analysis. Their morphological characters, both qualitative and quantitative, were studied and used to develop a morphology-based classification model to facilitate classification on large scale. Compared to using linear measurements only, inclusion of the qualitative carapace sculpturing character greatly improved the classification model. Field experiments were conducted to test the settlement preference of barnacles on substrates without and with biofilms of different ages. Higher number of barnacle settlement was found on substrates with aged biofilms compared to substrates without or with young biofilms. Characterization of biofilm successional profiles with respect to their bacterial and microeukaryotic compositions and biofilm structure were also carried out. Significant association was found between the successional changes in microeukaryote composition and the settlement of barnacle, but not with the bacterial composition or biofilm structure. All three successional profiles (bacteria, microeukaryotes, biofilm structure) were quantitatively shown to be concordant, indicating likely interactions among them and warrant future studies. Naturally-grown mangrove trees were observed to be less prone to biofouling than artificial substrate and re-planted mangroves. Abundant snail grazers were observed in the natural mangroves and exclusion experiments were conducted. Results showed that exclusion of grazers led to settlement of large number of barnacles and higher growth of microbial biofilms, suggesting grazing pressure, not anti-fouling activity from the trees, as the underlying factor regulating barnacle abundance on natural mangrove trees. Study on the snail behaviour was carried out to understand why grazing pressure on barnacles was not established in the re-planted mangrove plants. While strong collective movements and grazing activity of snails in tandem with the tidal cycle (to avoid submersion) were observed in natural mangrove trees, it may be difficult for such behaviours to form on replanted mangrove seedlings. (http://studentsrepo.um.edu.my/4915/)
... Furthermore, bacteria and their secreted substances were shown to influence diatom growth and EPS production (Bruckner et al., 2011). Other studies stated the important role of bacteria during diatom attachment (Gawne et al., 1998) and during the formation of diatom aggregates (Gaerdes et al., 2011). Furthermore, Lubarsky et al. (2010) demonstrated that this symbiosis between diatoms and bacteria had a direct impact on the overall biofilm network and was an essential driving factor for biofilm stability and biostabilisation. ...
Article
Fine sediments (fine sands or silts) are significantly impacted by microbial biostabilisation. This process complicates precise modelling solutions for sediment dynamics and management strategies for riverine sediment. The present publication investigates the effect of seasonality upon biostabilisation. In total, five straight flume experiments with fluvial water were performed during spring, summer and autumn under identical boundary conditions. The extracellular polymeric substances (EPS), microbial biomass and microbial community composition of the developing biofilms were analysed. In addition, biofilm adhesiveness was measured. Highest biostabilisation occurred during spring (up to six times greater than during autumn) and coincided with maximal EPS production - especially extracellular proteins indicating the essential role of adhesive proteins for the stability of the biofilm matrix. Furthermore, not biomass but microbial community composition significantly differed between seasons. For instance, during minimal biostabilszation in autumn, the diatom community was dominated by the motile diatoms Nitzschia fonticola and Nitzschia dissipata var. dissipata. Concurrently, the highest rates of change within the bacterial community were detected. This suggests a disruptive impact of diatom movement upon the biofilm matrix and overall biofilm stability. These findings emphasise the importance of detailed analyses of the microbial community and demonstrate the complex interactions of distinct biofilm features influencing the functionality of the overall biofilm system.
... Bacteria are known to influence diatom aggregation (Grossart et al. 2006;Gärdes et al. 2010) which possibly depends on the consumability of EPS (Grossart et al. 2006). Surface attachment and initial steps of biofilm formation of the diatom Achnanthes longipes were shown to be affected by bacteria (Gawne et al. 1998) and the diatom Cymbella microcephala showed capsules of bound EPS only in the presence of a satellite bacterium or its sterile spent medium while the axenic culture did not exhibit cell bound structures (Bruckner et al. 2008). ...
... Indeed, the presence of such biofilms induced either enhancement or a reduction in the number of settled algae depending of the test surface used. Gawne et al. (1998) have previously showed that single-species biofilms formed from Pseudomonas atlantica and associated EPS, reduced the settlement of the diatom Achnanthes longipes on polystyrene, enhanced it on glass while no effect was obtained on silicone coatings. Inhibitory effects on diatom settlement of single-species biofilms formed from a Pseudoalteromonas sp. on glass, have also been reported by Wigglesworth-Cooksey and Cooksey (2005). ...
Article
Previous studies have shown that bacterial biofilms formed from natural seawater (NSW) enhance the settlement of spores of the green alga Ulva linza, while single-species biofilms may enhance or reduce settlement, or have no effect at all. However, the effect of biofilms on the adhesion strength of algae, and how that may be influenced by coating/surface properties, is not known. In this study, the effect of biofilms formed from natural seawater and the marine bacterium Cobetia marina, on the settlement and the adhesion strength of spores and sporelings of the macroalga U. linza and the diatom Navicula incerta, was evaluated on Intersleek® 700, Intersleek® 900, poly(dimethylsiloxane) and glass. The settlement and adhesion strength of these algae were strongly influenced by biofilms and their nature. Biofilms formed from NSW enhanced the settlement (attachment) of both algae on all the surfaces while the effect of biofilms formed from C. marina varied with the coating type. The adhesion strength of spores and sporelings of U. linza and diatoms was reduced on all the surfaces biofilmed with C. marina, while adhesion strength on biofilms formed from NSW was dependent on the alga (and on its stage of development in the case of U. linza), and coating type. The results illustrate the complexity of the relationships between fouling algae and bacterial biofilms and suggest the need for caution to avoid over-generalisation.
... Conditioning consists of the accumulation of a layer of organic material and bacteria onto a substratum, which appears to facilitate the attachment process by diatoms (Cooksey & Wigglesworth-Cooksey 1995), including D. geminata (Bergey et al. 2010), and may alter colonisation patterns (Peterson & Stevenson 1989). The bacterial biofilm composition can also affect attachment rates (e.g., in A. longipes, Gawne et al. 1998). Because the community composition of biofilms appears to be linked to nutrient status (Lear & Lewis 2009, Lear et al. 2008, Lyautey et al. 2003, nutrient conditions may have an indirect effect on D. geminata attachment through their effect on the bacterial biofilm. ...
Article
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We measured cell attachments and stalk lengths of the stalked diatom Didymosphenia geminata in situ, using in vivo staining, under different nutrient (phosphorus and nitrogen) and light treatments. Our aims were: (1) to investigate the effects of light and temperature (season) on attachment and stalk growth, including the effect of ultraviolet radiation (UVR), which has been suggested as a possible factor favouring D. geminata proliferation; and (2) to test the hypothesis that enrichment with dissolved phosphorus (DRP) inhibits the initial attachment of D. geminata cells. Although low concentrations (below ∼ 2 mg m−3) of DRP appear to be responsible for D. geminata proliferation, its general absence where DRP>2 mg m−3 is not understood. The experiments were conducted in outdoor channels over 14 months, spanning a range of water temperatures and light intensities. Increasing visible light intensity usually had a positive effect on attachment densities and stalk length, but both were depressed by very high intensities. Exposure to UVR generally led to lower attachment rates and shorter stalks. Increasing water temperature with season had a positive influence on the proportion of cell attachments producing stalks. Elevated nutrients (up to 6.6 mg m−3 P, and up to 115 mg m−3 N above ambient) did not affect D. geminata cell attachment unless the treatment channels contained previously colonised substrata. Nutrient enrichment negatively affected stalk length. Earlier findings of a positive role of light and a negative effect of nutrients on stalk length in D. geminata were corroborated, except that photoinhibition was demonstrated at very high visible light intensities. There was no evidence of a positive effect of UVR on D. geminata proliferation at the initial stages of attachment and growth. The results indicated that the absence of D. geminata from rivers with high DRP concentrations is not the result of nutrient interference with initial cell attachment.
... Enhanced attachment to Parafilm suggests that biological or chemical substrate properties play a role in distribution patterns. This is consistent with previous reports of a stronger attachment to hydrophobic surfaces than to hydrophilic ones for several other diatoms (e.g., Gwane et al. 1998;Holland et al. 2004;Krishnan et al. 2006;Willis et al. 2007). In river ecosystems, most substrates are covered with a biofilm that is usually composed of a mixed assemblage of organic compounds, detritus, heterotrophic bacteria, cyanobacteria and algae. ...
Article
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Didymosphenia geminata is a freshwater diatom that can form extensive nuisance mats in rivers and streams. First detected in New Zealand in 2004, D. geminata has been found in over 150 rivers throughout the South Island. The diatom exhibited interesting distribution patterns in New Zealand, where it has remained absent from several apparently suitable habitats. The aim of this study was to investigate the role of New Zealand river water chemistry in the establishment of D. geminata. Water was collected from 16 North Island and four South Island rivers, and four South Island groundwater-fed creeks where D. geminata was absent, and from seven South Island rivers with low to medium levels of D. geminata and six South Island rivers with high levels of D. geminata. Water chemistry parameters were measured for these sites. The survival and attachment of D. geminata cells to the surface of culture plates were monitored in the laboratory under controlled conditions. Cells survived, attached and underwent cell division in waters with a wide range of chemistries, including water where D. geminata was absent. No correlation was found between cell survival, attachment, or division and any of the individual elements, compounds, or nutrient ratios tested. Findings in this study suggested that water chemistry, in isolation of other environmental parameters, was unlikely to be the sole variable responsible for D. geminata distribution in New Zealand. The attachment of free D. geminata cells to a substrate was a prerequisite for cell division, indicating that substrate composition may play an important role in D. geminata establishment.
... The consortia of microorganisms, algae and bacteria imbedded in a polysaccharide matrix and colonizing most substrates in surface waters are called biofilms. Autotrophic biofilms are currently the subject of a large number of studies focusing on the regulations of the organic carbon content in shallow environments (Battin et al. 1999), forming a crucial link at the base of the trophic web (Steinman 1996), purifying water (Percival et al. 2000) or, conversely, causing a nuisance by biofouling (Gawne et al. 1998). ...
Article
Biofilms in surface waters are characterized by their spatial structure and the heterogeneous distribution of the microorganisms that interact in a complex and dynamic way. Therefore, the assessment of phototrophic and heterotrophic biofilms' metabolic activity should be done without disturbing their structure. Several optical methods that allow the study of undisturbed living biofilms have been developed and are claimed to have high potential in the analysis of biofilms. However, natural biofilms can develop into thick packages of cells that may limit light penetration into the biofilm matrix, hindering the use of optical methods. In this paper we evaluate the use of non-destructive optical and destructive methods for the study of natural algal-bacterial biofilms. Pulse amplitude modulation (PAM) fluorimetry (with both single and multiple wavelength excitation) and confocal laser scanning microscopy (CLSM) are used as optical methods and compared to chemical extraction of plant pigments and exopolysaccharides. We demonstrate that the attenuation of the light intensity by the biofilm matrix represents a limitation to optical methods that is difficult to overcome in mature natural biofilms; but nevertheless, optical methods are very reliable for the study of thin or young biofilms. Apart from the biofilm thickness, the degree of compactness should also be taken into account. The density of some natural biofilms could be a limitation of CLSM especially if high molecular weight probes are used for specific biofilm components. In conclusion, a combination of both approaches still appears to be necessary in order to follow the complete developmental period of biofilms. [KEYWORDS: lms ; Microalgae ; PAM fluorimetry ; CLSM ; Chlorophyll ; Lectins ; Bacteria]
... Biofilms commonly cover submersed surfaces in shallow freshwater systems and have the capacity to modify the transport and accumulation of substances such as nutrients and suspended particles in the water (Lowe & Pan, 1996). Autotrophic biofilms have been the subject of numerous studies focusing on their role as regulators of the organic carbon content in shallow environments (Battin et al., 1999), as a crucial link at the base of the trophic web (Steinman, 1996) and in purifying water (Percival et al., 2000) or, conversely, the nuisance caused by biofouling (Gawne et al., 1998). ...
Article
The influence of external factors other than nutrients on biofilm development and composition was studied with a combination of optical (Confocal Laser Scanning Microscopy, PAM fluorometry) and chemical methods (EPS extraction, HPLC, TOC determination). The development of algal-bacterial biofilms was followed from bare surfaces to mature biofilms in two water reservoirs on Dutch filtration dunes. Biofilms developed under the influence of grazing, light limitation or undisturbed by either of these two factors. Biofilms appeared similar at the beginning of the colonization period at the three sites and laser microscopy observations revealed the predominance of bacteria and capsular EPS (extracellular polymeric substances) in young biofilms. After 3 weeks development, the biofilms had a higher number of taxa; undisturbed biofilms presented the highest biomass, the longest developmental period and showed a significant correlation between organic carbon, chlorophyll and EPS production, indicating a close coupling between autotrophic carbon production and EPS. In light-limited biofilms, this coupling was weaker (although the organic carbon content was similar to that of the undisturbed biofilms) and a lower algal biomass was reached. Light-limited biofilms were mostly composed of diatoms, which are more efficient in low irradiances than green microalgae. Biofilms grazed by the snail Potamopyrgus antipodarum presented the lowest biomass level, but the highest proportion of EPS. Grazing seemed to favour the predominance of EPS-rich algae, as well as firmly attached diatoms. Although filamentous cyanobacteria were found in mature biofilms at the three locations, they were more abundant in the grazed biofilms. The differences in carbon uptake with respect to its allocation indicated that external factors influencing biofilm development affect the cycling and transport of carbon in biofilms and hence influence the effect of biofilm metabolism on the overlying water quality.
... These initial biofilm organisms are known to produce exopolymers that assist the process of adhesion and movement (Molino and Wetherbee, 2008). So, the observed pat- tern of biofilm community development in natural systems (bacteria preceding algae) is more likely to be a reflection of the average abun- dance and the availability of the different colonizing forms at the mo- ment of immersion of a new substratum ( Gawne et al., 1998;Wahl, 1989). In view of this, considering the cell size, cell availability and cell abundance, since picophytoplankton are next to bacteria, it was hypothesized that picophytoplankton are the first autotrophic colo- nizers in biofilms contributing significantly to the biofilm photosyn- thetic biomass in the initial stages thereby playing an important role in the biofilm food web dynamics and probably in the production of exopolymers similar to bacteria and diatoms (Patil and Anil, 2005c). ...
Article
Although the importance of picophytoplankton (b3 μm) as the major primary producers is well established in the oceanic and coastal marine environment, occurrence of this community in the marine biofilms is not ex-plored. Considering their small size and high abundance which is next to bacteria, the initial heterotrophic col-onizers, it was hypothesized that picophytoplankton are the first autotrophic colonizers in marine biofilms. In this study biofilms were developed by immersing glass slides in the tropical waters of the Dona Paula Bay up to a period of 192 h. The presence of picophytoplankton and the temporal variations in community structure was investigated flow cytometrically after every 24 h. Biofilms were also developed in the laboratory by immersing the glass slides in fresh natural seawater and the sequence of appearance of the microorganisms was assessed with high frequency samplings. Field observations showed the presence of three groups of picophytoplankton, two prokaryotes, Prochlorococcus-like organisms (PRO), Synechococcus (SYN) and the picoeukaryotes (PEUK). Nanoeukaryotes, which are mostly represented by diatoms were also monitored. In the total biofilm commu-nity, prokaryotes were dominant throughout the study period wherein contribution of SYN was highest (50%) in the earlier stages which were later overtaken by PRO-like cells. The contribution of PEUK and nanoeukaryotes was always below 20%. Picophytoplankton contribution to the total photosynthetic biomass was > 60% in the initial period of biofilm formation, both in terms of numbers and biomass with PEUK as the major contributors. However, after 2 days of incubation, their contribution to total chlorophyll declined thus revealing that although their numbers were increasing, picophytoplankton were succeeded by nanoeukaryotes in terms of biomass. Laboratory experiments revealed that heterotrophic bacteria and pic-ophytoplankton appeared within 5 min in the biofilms which were followed by the nanoeukaryotes after 5 h. This study shows that picophytoplankton are the pioneer autotrophic colonizers in the tropical marine biofilms, suggesting an essential role in the biofilm food web dynamics, especially in the initial stages.
... In this case, a decrease in AHL concentrations might reflect changes in microbial composition. Changes in bacterial species composition and chemical compound production could possibly result in changes in diatom communities, as presence of particular bacteria affect recruitment of diatoms ( Gawne et al. 1998;Wigglesworth-Cooksey and Cooksey 2005). Alternatively, there is a possibility that kojic acid reduced formation of microbial communities by means other than QS inhibition. ...
Article
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Seventy eight natural products from chemical libraries containing compounds from marine organisms (sponges, algae, fungi, tunicates and cyanobacteria) and terrestrial plants, were screened for the inhibition of bacterial quorum sensing (QS) using a reporter strain Chromobacterium violaceum CV017. About half of the natural products did not show any QS inhibition. Twenty four percent of the tested compounds inhibited QS of the reporter without causing toxicity. The QS inhibitory activities of the most potent and abundant compounds were further investigated using the LuxR-based reporter E. coli pSB401 and the LasR-based reporter E. coli pSB1075. Midpacamide and tenuazonic acid were toxic to the tested reporters. QS-dependent luminescence of the LasR-based reporter, which is normally induced by N-3-oxo-dodecanoyl-L-homoserine lactone, was reduced by demethoxy encecalin and hymenialdisin at concentrations >6.6 μM and 15 μM, respectively. Hymenialdisin, demethoxy encecalin, microcolins A and B and kojic acid inhibited responses of the LuxR-based reporter induced by N-3-oxo-hexanoyl-L-homoserine lactone at concentrations >0.2 μM, 2.2 μM, 1.5 μM, 15 μM and 36 μM, respectively. The ability to prevent microfouling by one of the compounds screened in this study (kojic acid; final concentrations 330 μM and 1 mM) was tested in a controlled mesocosm experiment. Kojic acid inhibited formation of microbial communities on glass slides, decreasing the densities of bacteria and diatoms in comparison with the control lacking kojic acid. The study suggests that natural products with QS inhibitory properties can be used for controlling biofouling communities.
... Other bacterial species can produce antibiotic, anti-diatom compounds and quorum sensing inhibitors that can reduce attachment and growth of other microorganisms (reviewed by Dobretsov et al. 2006Dobretsov et al. , 2009. Bacterial composition and bacterial culture conditions affected attachment of the diatom Achnanthes longipes (Gawne et al. 1998). Additionally, the presence of bacterial biofilms on substrata with different physical properties either enhanced or inhibited attachment of this diatom. ...
Article
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The antimicrobial performance of two fouling-release coating systems, Intersleek 700® (IS700; silicone technology), Intersleek 900® (IS900; fluoropolymer technology) and a tie coat (TC, control surface) was investigated in a short term (10 days) field experiment conducted at a depth of ca 0.5 m in the Marina Bandar Rawdha (Muscat, Oman). Microfouling on coated glass slides was analyzed using epifluorescence microscopy and adenosine-5'-triphosphate (ATP) luminometry. All the coatings developed biofilms composed of heterotrophic bacteria, cyanobacteria, seven species of diatoms (2 species of Navicula, Cylindrotheca sp., Nitzschia sp., Amphora sp., Diploneis sp., and Bacillaria sp.) and algal spores (Ulva sp.). IS900 had significantly thinner biofilms with fewer diatom species, no algal spores and the least number of bacteria in comparison with IS700 and the TC. The ATP readings did not correspond to the numbers of bacteria and diatoms in the biofilms. The density of diatoms was negatively correlated with the density of the bacteria in biofilms on the IS900 coating, and, conversely, diatom density was positively correlated in biofilms on the TC. The higher antifouling efficacy of IS900 over IS700 may lead to lower roughness and thus lower fuel consumption for those vessels that utilise the IS900 fouling-release coating.
... Quantification methods are available from aquatic algal biofilms, since these colonise almost every substratum in shallow waters and form an important basis of the trophic web (Steinman, 1996). Studies of aquatic biofilms focus on the assessment of the spatial structure (Okkerse et al. 2000;Wimpenny et al. 2000;Barranguet et al. 2004) but also include studies of biofouling (Gawne et al. 1998) or microbial activity (Battin et al. 1999). ...
Article
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The aim of this study was to quantify algal colonisation on anthropogenic surfaces (viz. building facades and roof tiles) using chlorophyll a (chl a) as a specific biomarker. Chl a was estimated as the initial fluorescence F0 of 'dark adapted' algae using a pulse-modulated fluorometer (PAM-2000). Four isolates of aeroterrestrial green algae and one aquatic isolate were included in this study. The chl a concentration and F0 showed an exponential relationship in the tested range between 0 and 400 mg chl a m(-2). The relationship was linear at chl a concentrations <20 mg m(-2). Exponential and linear models are presented for the single isolates with large coefficients of determination (exponential: r2 > 0.94, linear: r2 > 0.92). The specific power of this fluorometric method is the detection of initial algal colonisation on surfaces in thin or young biofilms down to 3.5 mg chl a m(-2), which corresponds to an abundances of the investigated isolates between 0.2 and 1.5 million cells cm(-2).
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The biofilm-forming microalgae are known to experience periods of continuous darkness (upto several days), in addition to the natural day-night cycle, especially in the intertidal sediment regions (when transported to deeper sediments) and the ships’ ballast water tanks (during voyages). However, the information on community and physiological responses to different periods of darkness is limited. Here, the survival capability of biofilm-forming microalgae to varying periods of darkness (7-35 days) and the growth patterns upon resumption of normal 12h light:dark photocycle has been addressed through simulation experiments. Diatoms dominated the seawater biofilms, but the dark survival period varied and was species-specific. Of the 25 diatoms, only Amphora, potential toxin producer, followed by Navicula remained viable and photosynthetically healthy under darkness without undergoing asexual reproduction. Both diatoms are essential contributors to fouling and microphytobenthic community. Upon re-exposure of dark-adapted biofilms to 12h light:dark photocycle, the improvement in photosynthetic efficiency and resumption of growth via asexual-reproduction was observed. However, the lag-phase duration increased with a long dark history. Nevertheless, eurytolerant nature and high dark survival capability (with its quick response to light) of Amphora and Navicula indicated that they have the potential to colonize benthic-ecosystems thus impacting the benthic and fouling community.
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Corrosion has been persisting as the most severe concern for steel structures in the marine environment. Due to the widespread occurrence of biofouling, apart from the electrochemical corrosion, microbiologically induced corrosion (MIC) is an important factor that triggers the deterioration of marine steel infrastructures. Traditional anti-corrosion coatings usually lack the antifouling function, attachment and colonization of marine microorganisms therefore in most cases accelerate the existing corrosion damage. Anti-corrosive coating fabricated by thermal spray has been extensively applied for the marine corrosion prevention, yet the anti-MIC coatings deposited by thermal spray technical route still keep elusive. Developing thermal-sprayed coatings with dual anti-corrosion and antifouling performances is the key to combating MIC. In this review, most recent advances in understanding biofouling and developing antifouling and anti-MIC techniques are surveyed. The formation and evolution of MIC and biofouling, and the effect of microbial biofilm on their occurrence are addressed briefly. Strategies involving the use of chemical methods, physical methods and biological methods to prevent MIC and biofouling are discussed. Selection and design of thermal spray coating materials with desired corrosion resistance and antifouling performances are reviewed. Current perspectives and future possibilities of thermal-sprayed marine coatings for long-term anti-MIC applications are also discussed.
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Motile diatoms move in the low Reynolds number regime without any apparent organelle for motility. While several possible hypotheses have been proposed, the diatom motility mechanism is not fully understood. In this study, the kinematics of the jerky motion of individual diatoms was investigated at 1.2 millisecond temporal and 9 nm subpixel spatial resolution of species: Nitzschia palea, Navicula cryptocephala, Navicula sp. Centroids of the diatoms were measured from 821 fps digital movies using algorithms for particle tracking. The examination of the displacement data indicated that: 1) for all the diatoms investigated, speed along its trajectory varied from one frame to the next; 2) the motion was not unidirectional; 3) the displacement data included rare large velocities that were as large as 250 εm/s for the Navicula diatoms . The calculated spontaneous accelerations are on the order of 5 × 10 ⁵ εm/s ² . Rapid changes in the orientation angle as large as 2.66 rad/s were observed for Nitzschia palea . The jerky diatom motion could be related to elastic snapping and recoil at the yield point and/or explosive discharge of the mucilage secreted and left on the glass substrate as the “diatom trail.” The flow of mucilage in the slits in the diatom silica valve, called raphes, could be a first example of “active nanofluidics,” which we define as self-propulsion of a fluid. Active nanofluidics could be useful in designing micro- and nanorobots that require pumps for fluid flow.
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Phototrophic biofilms may be defined as interfacial microbial communities mainly driven by light as energy source. Structure, productivity and taxonomic composition of freshwater phototrophic biofilms under different growth conditions were investigated within the EU-project PHOBIA with the following aims: 1) optimisation of wastewater treatment in wetlands, 2) control and prevention of biofouling on submersed objects, and 3) modelling of phototrophic biofilm development. Experiments were carried out in a flow-lane incubator with precise control of external light, temperature, velocity conditions and nutrient-adapted artificial medium. Structure and architecture of phototrophic biofilms at different developmental stages were examined by using multi-channel confocal laser scanning microscopy (CLSM). The development of phototrophic biofilms was clearly light dependent. Fast growing phototrophic biofilms were mostly dominated by single species algae and formed less stable structures of up to 900 μm thickness. Biofilms with these dimensions had to be cryo-sectioned and post-stained for CLSM. Laser microscopy analysis also revealed a stratification of phototrophic organisms which was more pronounced in slow growing biofilms. In contrast, at very low light intensity the development of phototrophic biofilms was strongly delayed. In conclusion, structural features and subsequent functional relationships may be key parameters for exploitation, control and modelling of phototrophic biofilms.
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Diatoms are tenacious fouling organisms and have been observed to remain on ship hull coatings at speeds in excess of 30 knots. This study was designed to investigate the adhesion of diatoms to three fouling release ship hull coatings, Intersleek 700 (IS 700), Intersleek 900 (IS 900), and Hempasil X3 (HX3) and one reference coating Dow Corning 3140 (DC 3140), that were exposed at a static immersion test site. The coatings were subjected to water jet testing to determine biofilm adhesion and the subsequent pressures needed to remove specific diatom species. Differences in community composition were observed among coatings in the pre and post water jet evaluation. All diatoms were removed from HX3 after 0.08 MPa; however, the pressure required to completely remove biofilm and diatoms on DC 3140, IS 700, and IS 900 varied. Biofilm removal pressure ranged from 0.08 to 0.40 MPa on DC 3140, 0.16 to 0.40 MPa on IS 700, and 0.08 to 0.40 MPa on IS 900. Significant differences were observed among coatings for removal pressure, as well as initial diatom abundance; however, differences were dependent on the sampling date. The diatom genera which required the highest pressure for removal from the fouling release coatings were Achnanthes, Amphora, Cocconeis, Navicula, and Synedra. The results show differences in the adhesion strength of diatoms to different fouling release coatings and highlight those species, which have the potential to contribute to biofilms remaining on ship hulls once a vessel is underway.
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Diatom adhesion to different gel surfaces was tested under different shear conditions, using the fouling marine diatom Amphora coffeaeformis as test organism. Four polymers were selected to obtain a test matrix containing gels with different surface charge as well as different surface energies, viz. agarose, alginate, chitosan and chemically modified polyvinylalcohol (PVA‐SbQ). Three experimental systems were applied to obtain different shear rates. Experimental system 1 consisted of gels cast in a cell culturing well plate for comparing initial adhesion as well as long term biofilm development in the absence of shear. In experimental system 2, microscope slide based test surfaces were tested in aquaria under low shear conditions. A rotating annular biofilm reactor was used to obtain high and controlled shear rates. At high shear rates A. coffeaeformis cells adhered better to the charged polymer gels (alginate and chitosan) than to the low charged polymer gels (agarose and PVA‐SbQ). In the system where shear was absent A. coffeaeformis cells developed a biofilm on agarose equivalent to the charged polymer gels, while adhesion to PVA‐SbQ remained low at all shear rates. It is concluded that non‐solid surfaces did not represent an obstacle to settling and growth of this organism. As observed for solid surfaces, low charge density led to reduced attachment, particularly at high shear.
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The initial phases of subtidal and intertidal community development were observed using scanning electron microscopy on samples from plastic panels immersed monthly in the St. Lawrence Estuary.Bacteria and diatom populations were quantitatively evaluated on samples collected from May to November, 1978. The pattern of immersion and/or periodical emersion according to the level greatly influenced the community structure. Subtidal panels (−5.0 m) were rapidly colonized by bacteria while diatoms settled 2–7 wk later, depending on the season. Cocconeis spp. and Amphora spp. were the major diatom colonizers until mid-August. In September, Synedra tabulata settled on the panels. Until mid-September, all dominant species formed well-defined, generally monospecific clumps. In contrast with Cocconeis spp. and Amphora spp., which lie horizontally on the surface, S. tabulata, which is needlelike in shape, formed erect fan-shaped colonies. Other late invaders possessed a mucus stalk, raising themselves from the surface and thus better utilizing the vertical dimension. Clump overlap and increased species interactions occurred with higher cell densities. In the intertidal zone bacteria settled after 8–12 wk while Achnanthes brevipes var. parvula appeared after 20 wk, the only diatom species able to resist semidiurnal emersion. The ability of the panels to retain water through detritus and irregularities is probably the main factor allowing the development of this community. Panels emersed only at spring tides (monthly) were rapidly colonized by bacteria, and heavy diatom settlement occurred within 4 wk. Successive monthly emersions eliminated or strongly reduced diatom populations, which were replaced by filamentous (Ectocarpaceae) algae. The three types of communities are compared and the strategic advantage of upright forms is discussed in relation to population density, light availability, and detrital cover.Key words: St. Lawrence Estuary, artificial substrate, community structure, community development, Cocconeis spp., Synedra tabulata. Amphora spp., diatoms
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Biofilm communities in the euphotic zone of aquatic habitats comprise photoautotrophic microorganisms, such as diatoms, green algae and cyanobacteria, which produce the organic carbon that fuels the life of a heterotrophic contingent of microorganisms, mostly bacteria. Such photoautotrophic-heterotrophic mixed-species biofilms have received little attention in biofilm research due to a lack of suitable pure-culture laboratory model systems. However, they offer important insight into microbial population dynamics and community interactions during a biofilm-developmental process that shapes highly structured, extremely well-adapted microbial landscapes. Here, we report on the development of a sterile incubation chamber for growing and monitoring axenic phototrophic biofilms, i.e. a sterilizable, illuminated, continuous-flow system for a routine work with pure cultures. The system has been designed to simulate the growth conditions in the shallow, littoral zone of aquatic habitats (horizontal surface, submerged in water, illuminated, aerated). Additional features of the concept include automated photometrical monitoring of biofilm density (as biofilm turbidity), analysis via confocal microscopy, direct harvesting of cells, and options to control illumination, flow velocity, and composition of culture fluid. The application of the system was demonstrated in growth experiments using axenic diatom biofilms, or axenic diatom biofilms co-cultivated with different bacterial strains isolated from epilithic biofilms of an oligotrophic freshwater lake.
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We have answered fundamental questions regarding the mechanisms of attachment and the nature of the biocomposite adhesives utilized by the marine biofouling diatom Achnanthes longipes and the freshwater Cymbella cistula. During the course of this grant we have: (1) delineated the sequence of events involved in attachment of the organisms to a variety of surfaces; (2) discovered that initial adhesion is mediated by different methods/polymers on hydrophilic surfaces vs. those more hydrophobic and that bacterial 'preconditioning' has variable effects on adhesion; (3) developed methodology for mass culture of fouling diatoms and isolation of adhesive components; (4) characterized the 'proteoglycan' bioadhesives using monosaccharide and methylation analysis, NMR and other analytical techniques; (5) localized specific carbohydrate moieties of the adhesive with lectins and produced monoclonal antibodies against the adhesives and applied them as probes of structure/function of the adhesives; (6) determined that adhesion is disrupted at several levels by dichlorobenzonitrile (DCB) and related specific inhibitors of plant extracellular polysaccharide synthesis; (7) ascertained that DCB and other potential anti-fouling chemicals act intracellularly on an 18 KD membrane associated protein and that DCB doped polyimide surfaces do not inhibit adhesion; (8) discovered that adhesive structures are not assembled in the presence of high concentrations of iodide and that bromide is a limiting requirement for adhesion; and (9) created an expression library to screen for a 50 kD polypeptide from the adhesive and a peroxidase involved in crosslinking the adhesive.
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A comparative study of two commercially available elastomers, RTV11™ and Intersleek™, has been conducted employing atomic force microscopy (AFM) and surface and bulk analysis techniques. The results confirmed the presence of CaCO3 (rhombohedral calcite) filler particles in RTV11 and revealed TiO2 (tetragonal rutile) and Fe3O4 (cubic magnetite) as filler particles in Intersleek formulation. Time-of-flight secondary ion mass spectroscopy (TOF-SIMS) depth profiling revealed average threshold depths of ∼100 nm for the onset of filler particles. Indentation curves obtained from AFM force-volume imaging demonstrated that the presence of these particles significantly alters the local elastic properties of the coating. While the particle-free, high-compliance regions followed Hertzian behavior to a reasonable approximation, the low-compliance domains, where the subsurface filler particles reside, showed a significant deviation from this model. The Hertzian model, applied to the particle-free regions, gave values of 3.0, 1.9, and 1.4 MPa, respectively, for the elastic moduli of thin RTV11, thick RTV11, and Intersleek. For thin and thick RTV11 the presence of subsurface particles caused a local increase in the elastic moduli of the polymers, resulting in values 2.1 and 1.7 times higher than those for the particle-free regions of the corresponding polymers. For Intersleek, this increase was only 1.3 times. TOF-SIMS analysis did not reveal local differences in the chemical composition of the polymers, hence the inhomogeneities in the microelastic properties of these polymers are explained in terms of differences in the physical properties of these regions. Subsurface filler particles undergo substantial elastic displacements under the influence of the penetrating AFM tip. © 2003 American Institute of Physics.
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Larval settlement is a critical stage in the artificial production of Argopecten purpuratus. The study investigated the feasibility of improving post-larval settlement of this species using a substrate (cultch) that was pre-treated with a biofilm of native diatoms. Four species of diatoms were isolated from the surface of collectors that had high numbers of juvenile scallops (spat). These four species were able to attach themselves and grow on a polystyrene substrate. Scallop post-larval settlement was evaluated experimentally in two ways: (1) laboratory experiments in 10-L buckets; and (2) under natural condition by in situ experiments at the Marine Reserve “La Rinconada” (Antofagasta, Chile). Effects of biofilm treatments were examined using collectors that were coated with diatoms and collectors handled using normal method (new netlon held in filtered seawater that did not have a biofilm). Results of the laboratory experiments showed a higher percentage of A. purpuratus post-larval settlement on collectors coated with Fragiliaropsis pseudonana compared with control collectors (P>0.05). Results comparing biofilm of the diatoms F. pseudonana and Navicula veneta higher settlement on collectors pre-treated with N. veneta (1.156 ± 172 spat per collector -1 ). Statistical analysis showed that the addition of biofilms enhanced spatfall and always produced larger settlement compared with untreated collectors. These results indicate that addition of cultures diatom biofilms improves scallop larval settlement.
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The dominant presence of marine diatoms fouling the latest non-toxic, antifoul coatings has increased interest in characterising diatom adhesives and the mechanisms of their adhesion. In this study the adhesion of two benthic, fouling diatoms [Craspedostauros australis Cox and Haslea sp. Simonsen (Bacillariophyceae, Ochrophyta)] was measured on 23 test surfaces with different chemical properties. The adhesion of the diatoms was measured using a simple and effective bench-top flow chamber. Self-assembled monolayers were used to create a range of surfaces with specific chemical properties, allowing the direct assessment of adhesion strength to substrata with different chemical properties. PDMSe-[poly(dimethyl siloxane) elastomer], 'Intersleek'((R)), gold-coated glass slides, and acid-washed glass were also tested. No single chemical functional group was found that significantly reduces the adhesion of the diatoms. However, results show a negative linear correlation between the percentage of cells removed (C. australis 80%-0%, Haslea sp. 60%-0%) and surface contact angle (7 degrees-105 degrees) both species adhering more strongly to hydrophobic surfaces. This study introduces a simple, inexpensive and reliable bench-top flow chamber and shows that the adhesion of biofouling diatoms is mainly influenced by the physical properties of surfaces as defined by wettability.
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The composition of diatom-associated bacterial communities was studied with 14 different unialgal xenic diatom cultures isolated from freshwater epilithic biofilms of Lake Constance, Germany. A clear dominance of Alphaproteobacteria was observed, followed by Betaproteobacteria, Gammaproteobacteria, Bacteroidetes, and Verrucomicrobia. Pure cultures of the diatom Cymbella microcephala, which was found to be dominant in epilithic biofilms in Lake Constance, were cocultivated with six associated bacterial strains. All these bacterial strains were able to grow in C. microcephala cultures in the absence of organic cosubstrates. Diatom growth was generally enhanced in the presence of bacteria, and polysaccharide secretion was generally increased in the presence of Proteobacteria. The monomer composition of extracellular polysaccharides of C. microcephala changed in relation to the presence of different bacteria, but the dominant monomers were less affected. Our results indicate that these changes were caused by the diatom itself rather than by specific bacterial degradation. One Bacteroidetes strain strongly influenced carbohydrate secretion by the alga via extracellular soluble compounds. Biofilms were formed only in the presence of bacteria. Phylogenetic analysis and coculture studies indicate an adaptation of Proteobacteria and Bacteroidetes to the microenvironment created by the diatom biofilm.
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Most wetted surfaces that are illuminated support a population of phototrophs. The marine sediment is no exception and there the major component of the microphytobenthic population is diatoms. These organisms are credited with stabilizing the sediment against physical disturbance by virtue of the extracellular carbohydrate polymers that they elaborate. However, diatoms synthesize and secrete several carbohydrate polymers and it is not certain which of them is involved in the stabilization process. In order to investigate this, we have constructed small glass bead-filled flow through bioreactors to mimic marine sediments. The flow rate through the bioreactors was found to reflect the physical stability of the bead bed. Thus flow rate was measured as a function of diatom growth and the production of three operationally-defined polymers, i.e., those soluble in the medium, those soluble in 0.5 M NaHCO3 at 90 degrees C and those not soluble in either solvent (matrix polymer). Growth of the diatoms did not change the hydraulic conductivity of the bioreactors. For Amphora coffeaeformis, neither did the production of medium-soluble nor NaHCO3-soluble polymers. However, matrix polymer accumulation was directly correlated with a reduction in flow (regression coefficient R2 = 0.96) and stabilization against physical disturbance. Results with species of Navicula were not as clear. Both NaHCO3-soluble and matrix polymers were involved in producing the flow reduction. In the same manner we also measured the effect of Pseudoalteromonas haloplanktis growth on bead bed hydraulic conductivity and bead bed stability. Growing alone, no effect was found, but in co-culture with a single diatom species, the bacteria reduced the diatom effect on flow through the bioreactors seen earlier, however did not reduce the extent of their growth. Confocal scanning laser microscopy of beads colonized with diatoms alone, or diatoms in co-culture with bacteria, revealed that P. haloplanktis was able to inhibit diatom adhesion to the beads. When the bacteria were present there was less matrix polymer evident. We speculate that this interference with diatom metabolic activity was either the result of less matrix polymer synthesis, or its hydrolysis by the bacteria. The results are applicable to mixed species biofilms of this type on surfaces other than sediments.
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The formation of bacterial biofilms is usually an essential prelude to the development of marine fouling communities. The pioneering bacterial community is preceded by the sorption of a conditioning film of polymers from the sea. Primary attachment of bacteria involves chemotaxis of motile bacteria, reversible sorption and finally, permanent attachment of the primary bacterial film by polymeric fibrils. Bacterial slimes can be prevented by coating surfaces with chemicals that induce negative chemotaxis. Algal attachment to surfaces appears to involve both positive chemoreception and attachment of specific proteins to bacterial polysaccharides. Algal fouling can also be controlled by repellent chemicals. Recent developments in sediment deposition is discussed. (from authors' abstract)
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The effects of films of two strains of a marine bacterium, Deleya marina (ATCC 25374 and 27129) on the attachment response of cypris larvae of the balanomorph barnacle, Balanus amphitrite, were examined in the laboratory. Tests showed that the cell-surface hydrophobicities of the two bacteria in suspension were different. In contrast, films derived from these cells were both highly wettable (i.e., displayed high surface free energy). Assays (22 hours) compared permanent attachment of larval barnacles to films derived from exponential and stationary phase cells for both bacteria. These films either had no effect or inhibited attachment of both 0-day- and 4-day-old cypris larvae when compared with unfilmed controls. Our data indicate that inhibition of larval barnacle attachment by films of the two bacteria is the result of factors other than surface free energy. Production of chemical barnacle settlement inhibitors by the bacteria is hypothesized.
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Larvae of the barnacle Balanus amphitrite amphitrite Darwin (Crustacea: Cirripedia) respond to microbial surface film cues at settlement (i.e. attachment and metamorphosis). The effects of films of varying ages on the settlement behaviour of B. amphitrite cyprids were examined in laboratory choice assays using substrata preconditioned in natural seawater for longer periods (up to 18 d) than previous studies. Furthermore, in this study only known numbers of cyprids (either 1 or 20 larvae) per film treatment were investigated, allowing assessment of possible behavioural interactions between larvae. Quantitative analyses of the multi-species films permitted objective comparisons between film age treatments. A general trend of a reversal of the effect of filming on cyprid settlement response - from inhibitory to facilitatory - was noted with increasing film age and isolated cyprids responded similarly to groups of 20 cyprids. Microbial abundance and overall biotic diversity were found to be markedly greater in 'older' films. The facilitation of cyprid settlement by 'older' films contrasts with previously published studies on B. amphitrite and may be explained either by the greater ages of films assayed in the present study or qualitative/quantitative differences in films between studies.
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Olshausenstr. 40-60, D-2300 Kiel, Federal Republic of Germany . ABSTRACT. In the marine environment any solid, exposed undefended surface will become fouled. Similarly, fouling may effect numerous species which are able to tolerate a certain degree of epibiosis. In contrast, many others actively maintain t h e ~ r body surface clean of epibionts ('antifouling'). This paper illustrates aspects of the epibiosis/antifouling complex and discusses the omnipresence of fouling pressure, the first stages in the establishment of a fouhng community, the benefits and disadvantages of epibiosis for both epi-and basibionts, and possible anbfouling defense adaptations.
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The effects of marine bacteria on the attachment of cypris larvae of the barnacle Balanus amphitrite were investigated in the laboratory. Initial experiments included the effect of different species of bacteria, cyprid age, and bacterial film age on cyprid attachment. Additional studies examined the substratum/bacterial film interactions and their effect on cyprid attachment, and the effect of bacterial extracellular products on larval attachment. Data indicate that: (1) microbial films can influence attachment by cypris larvae; (2) films composed of single species of bacteria can influence attachment by stimulation and inhibition; (3) attachment by older larvae continues to be inhibited by some bacteria; (4) when films of some inhibitory bacteria are aged they become even more inhibitory to larval attachment; (5) the same bacterium adsorbed on different substrata elicits different attachment responses by the larvae; and (6) bacterial exopolymers appear to be involved in the larval attachment response. The exact nature of the bacterial components involved in the larval response is unknown.
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Films of bacteria on solid substrata can positively or negatively influence the attachment of marine invertebrate larvae. Effects of marine bacteria on the attachment of cypris larvae of the barnacle Balanus amphitrite Darwin were examined in the laboratory. Bacteria, grown to mid-exponential phase and allowed to adsorb irreversibly to polystyrene petri dishes, attached in densities of 107 cells cm-2. Assays (22h) were used to compare the effects of adsorbed cells of 18 different bacterial species on larval barnacle attachment. Most of the adsorbed bacteria either inhibited or had no effect on larval attachment compared to clean surfaces. Experiments testing the effect of larval age on barnacle attachment were conducted with six species of bacteria and showed that older larvae attached in higher percentages to clean surfaces and that bacterial films generally inhibited larval attaschment. Both the species of bacteria and the in situ age of the adsorbed bacteria affected barnacle attachment response: older films of Deleya (Pseudomonas) marina were more inhibitory. Bacterial extracellular materials may be involved in the inhibitory process.
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Larvae of the spirorbid Janua (Dexiospira) brasiliensis Grube settle on multi-species microbial films grown in laboratory aquaria. Bacteria appear to be responsible for inducing metamorphosis. Larvae of Janua rarely settled on films of the diatom Nitzchia. The larvae settled on pure culture films of bacteria isolated from the green macroalga Ulva lobata, a common natural substratum for Janua(Dexiospira) brasiliensis. Individual bacterial strains varied in their capacity to induce settlement and metamorphosis. Our data suggest that the metamorphic cue is associated with the surface of selected bacterial species.
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Extracellular adhesives from the diatoms Achnanthes longipes, Amphora coffeaeformis, Cymbella cistula, and Cymbella mexicana were characterized by monosaccharide and methylation analysis, lectin-fluorescein isothiocyanate localization, and cytochemical staining. Polysaccharide was the major component of adhesives formed during cell motility, synthesis of a basal pad, and/or production of a highly organized shaft. Hot water-insoluble/hot 0.5 M NaHCO3-soluble anionic polysaccharides from A. longipes and A. coffeaeformis adhesives were primarily composed of galactosyl (64-70%) and fucosyl (32-42%) residues. In A. longipes polymers, 2,3-, t-, 3-, and 4-linked/substituted galactosyl, t-, 3-, 4-, and 2-linked fucosyl, and t- and 2-linked glucuronic acid residues predominated. Adhesive polysaccharides from C. cistula were EDTA-soluble, sulfated, consisted of 83% galactosyl (4-, 4,6-, and 3,4-linked/substituted) and 13% xylosyl (t-, 4f/5p-, and 3p-linked/substituted) residues, and contained no uronosyl residues. Ulex europaeus agglutinin uniformly localized [alpha](1,2)-L-fucose units in C. cistula and Achnanthes adhesives formed during motility and in the pads of A. longipes. D-Galactose residues were localized throughout the shafts of C. cistula and capsules of A. coffeaeformis. D-Mannose and/or D-glucose, D-galactose, and [alpha](t)-L-fucose residues were uniformly localized in the outer layers of A. longipes shafts by Cancavalia ensiformis, Abrus precatorius, and Lotus tetragonolobus agglutinin, respectively. A model for diatom cell adhesive structure was developed from chemical characterization, localization, and microscopic observation of extracellular adhesive components formed during the diatom cell-attachment process.
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The capacity of benthic cyanobacteria to adhere to solid substrates was examined in terms of their cell surface properties. By using a biphasic water-hydrocarbon test system, it was demonstrated that benthic cyanobacteria from divergent habitats were all hydrophobic, whereas all the planktonic cyanobacteria tested were hydrophilic. Divalent cations were found more efficient than monovalent cations in effecting the expression of hydrophobicity. Mechanical shearing of the cell surface, as well as chemical removal of the cell wall, demonstrated that the hydrophobicity was confined to the outer surface layers. The hydrophobic sites were distributed along the whole length of the cyanobacterial filament. Hydrophilic hormogonia of benthic cyanobacteria became hydrophobic within 48 h when grown in the light; chloramphenicol, 3(3,4-dichlorophenyl)1,1 dimethylurea, or incubation in the dark prevented this transition. Hydrophobicity of Phormidium filaments was masked in late stationary phase; this effect was removed by gentle washing.
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Marine microbiologists have known for many decades that when an object is submerged in the sea, it is quickly colonized by marine bacteria which attach to its surface (ZoBell and Allen, 1935). Yet, we still know very little about the attachment mechanism(s), what conditions favor adhesion and how the attached, or sessile, micro-organisms are influenced by the proximity of the substratum. Moreover, we are further limited by not knowing the general applicability of the data which we do have. Are the few organisms which have been studied truly representative of most marine bacteria? Also are we justified in relating data from marine and freshwater environments, as is frequently done ? These are important reservations to be kept in mind during the following chapter.
Chapter
This chapter discusses an investigation of the marine fouling diatom communities on both nontoxic and toxic test panels suspended from a raft in Langstone Harbor, South Coast of England. A general comparison is made between the floristic composition of these two surface types, which is related to aspects such as the quality and quantity of incorporated antifouling biocide and various environmental parameters, such as depth of immersion of the panels and water temperature. The formation of a primary film and biofouling layers on a surface is influenced by a number of factors including sea–water chemistry, turbulence, temperature, light, and incorporated antifouling biocides. Several reports have drawn attention to the effect of depth on the development of benthic diatom communities. Amphora was by far the most abundant genus within the biofouling layer, other prominent genera being Navicula, Cocconeis, and Synedra. The diversity index method allowed comparison of diatom communities from month to month and it was evident that Amphora coffeaeformis var. perpusilla was the dominant diatom species in most samples.
Chapter
This paper will provide a framework for understanding the process of biofilm development in the context of stoichiometry and kinetics. Biofilm development is described in terms of selected fundamental rate processes and environmental parameters which influence their rate and extent. The properties of the biofilm and its microenvironment lead to topics of microbial ecology within the biofilm and the physiology of the organisms immobilized within it. These topics will be discussed in terms of unstructured models for the microbial processes.
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This chapter elaborates the control of fouling by nonbiological systems. The impact of fouling includes the loss of efficiency of ships, buoys, pilings, offshore platforms, sonar domes, and a variety of piping systems. Fouling has been controlled traditionally by antifouling paints that prevent settlement of organisms through the release of biocides, chiefly metallic e.g., copper, or organometallic compounds e.g., triorganotins. Amphora was chosen for laboratory studies because of its importance in shipfouling and for its ease of culturing and rapid attachment to surfaces. In spite of being derived from a clonal culture, differences in the adhesive capacity of cells between cultures occur. The results to date with RTV silicone elastomers indicate them to be worthy of more study as nonbiocidal antifouling systems. Their physical properties of poor abrasion resistance and tear strength limit the range of possible applications to situations where such characteristics are not of primary importance e.g., aquaculture, offshore structures, piping systems and power station water intakes.
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Changes in the electrical charge that occur on the surfaces of tests particles of quartz, germanium, and an anion-exchange resin when they are exposed to natural and artificial seawater have been studied by means of microelectrophoresis. Although the materials all assumed surface charges in a moderately electronegative range when immersed in natural seawater, they showed pronounced differences in charge consistent with their inherent chemical nature when exposed to seawater pretreated with ultraviolet irradiation to photo-oxidize organic matter. The characteristic surface charge exhibited by solids in seawater thus appears to be due to adsorbed organic constituents. The possibility that minor inorganic constituents of seawater might play a significant role in determining the surface charge of solids in natural seawater is unlikely because the surface charges wre nearly the same in photo-oxidized seawater and in an artificial seawater of the same salinity containing only major inorganic components.
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A maize (Zea mays L.) cDNA clone (pZMB2) encoding [beta]-amylase was isolated from a cDNA library prepared from the aleurone RNA of germinating kernels. The cDNA encodes a predicted product of 488 amino acids with significant similarity to known [beta]-amylases from barley (Hordeum vulgare), rye (Secale cereale), and rice (Oryza sativa). Glycine-rich repeats found in the carboxyl terminus of the endosperm-specific [beta]-amylase of barley and rye are absent from the maize gene product. The N-terminal sequence of the first 20 amino acids of a [beta]-amylase peptide derived from purified protein is identical to the 5th through 24th amino acids of the predicted cDNA product, indicating the absence of a conventional signal peptide in the maize protein. Recombinant inbred mapping data indicate that the cDNA clone is single-copy gene that maps to chromosome 7L at position 83 centimorgans. Northern blot analysis and in vitro translation-immunoprecipitation data indicate that the maize [beta]-amylase is synthesized de novo in the aleurone cells but not in the scutellum during seed germination.
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Diatom communities developing on plastic oyster spat collectors were sampled regularly over a 24-month period by weekly, fortnightly and monthly exposures of collectors at 15, 75 and 150 cm depths. Less than 25% of all species encountered were present continuously through the open water period May to December. Species composition of the Community and total density of diatoms varied with season and with duration and depth of exposure.
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Effects of current velocity and light energy on the taxonomica and physiognomic characteristics of periphyton assemblages were investigated in laboratory streams. The initial rate of colonization was related to current velocity, while the effects of light energy accounted for differences in species composition by the end of the experiment. Although the laboratory systems had many species in common during the realy stages of colonization, the experimental treatments generated differences in rates of communitydevelopment. synedra spp. were the early coloniters of the substrate, followed by an understory of Achnanthes spp. After day 16, Stigeoclonium tenue developed in the streams exposed to the higher photon flux density, but was rare in the shaded streams. The applicability of traditional successional theory to develoopmental patterns in lotic periphyton assemblages is discussed.
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When pennate diatoms adhere they do so by the secretion of an adhesive polymer. By the use of chemosensing leading to directed motility as an analogous system, potential sources of extracellular signals for this secretion have been examined. Evidence has accumulated that sensing of simple sugars (D‐glucose, D‐mannose) involves specific receptors and a Ca flux. The evidence is discussed in terms of a receptor‐controlled secretion model for diatom adhesion. Means by which surfaces may be sensed by diatoms are proposed. It may be possible to design antifoulant molecules that interfere with surface‐sensing by binding to chemosensory receptors.
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One of the most fundamental and precarious stages in the life history of a marine benthic alga is the colonization of a new substratum. For the majority of algae this is achieved by the formation and detachment of different types of highly specialized reproductive propagules which are then dispersed via the pelagic zone. This paper reviews the process of “settlement”, “attachment” and “establishment” of these propagules. Particular attention is given to the influence of substratum surface properties, both physical and chemical, on these processes, along with aspects of the derivation, chemical composition, mechanisms of release and mode of action of the various adhesives secreted by the attaching spores and germlings.
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These pages describe relatively simple and reliable methods for the culture of marine phytoplankton species useful for feeding marine invertebrates. The methods suffice for the most fastidious algae now routinely cultivable, and simplifications indicated for less demanding species are easily made; for example, omission of silicate for plants other than diatoms. Certain modifications of techniques, ancillary methods, and precautions will be treated briefly because questions often arise concerning them, but documentation will be minimal and hopefully restricted to publications readily available.
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A new method to measure adhesion force, or that force that holds surfaces in molecular contact, is used to quantify the effect of natural surface films on adhesion between surfaces immersed in seawater. Results of measurements demonstrate that bacterial films significantly modify surface adhesion and that the resulting interfacial force is nearly independent of bulk material composition. Where surfaces are hydrophilic and of similar surface charge, as is typical of surfaces in seawater, formation of bacterial films should cause a marked increase in adhesion force. A reduction in adhesion force observed for surfaces in seawater of low biological activity is attributed to adsorption of a surface active conditioning film, while a further reduction in adhesion force sometimes observed under bloom conditions remains unexplained. A broad range of adhesion forces corresponding to different sites on a surface can be understood in terms of surface microheterogeneity. Adhesion force measurements may be key for understanding steady state aggregate size, the timing of the sinking of blooms, and formation of oxygen-minimum layers. Understanding the nature of surfaces immersed in sea- water is essential to understanding particle aggregation and disaggregation and the effects that these processes have on sedimentation of particulate matter in the ocean. The dynamics of particles in seawater has been the subject of many experimental and theoretical treatments in the
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Glass microscope slides were immersed in the tiny Headwaters of a midwestern stream Achnanthes lanceolata (Bréb.) Grunow was the dominant or co-dominant species in 14 out of 15 one-month-old communities over a two-year period. Minutely streaked, periphyton-free areas mostly lacked live diatoms but had cell-free mucilage pads and attached raphe valves of A. lanceolata. These pads, secure or peeling, had a distinct bas-relief impression of the raphe valve. Pad mucilage was associated with the puncta and raphe, and its presence in the puncta of raphe valves maximizes the surface for valve/substrate adhesion. Periphyton-free streaks in otherwise stable periphyton may represent areas where abrasion or grazing had killed or removed cells without dislodging the mucilage-secured raphe valves or valve-free mucilage pads. Important adaptive features of A. lanceolata for resisting graying and/or stream hydrodynamic forces appear to be: a sessile, low-profile, lanceolate life form with rounded apices; an attached raphe valve, with a slightly concave valve face where mucilage accumulates and remains in the puncta of recessed, concave striae, and may also surround the valve-face/mantle edge; a slightly convex opposing pseudoraphe valve, with a rounded valve-face/mantle edge. Predictions for sibling cell inheritance in A. lanceolata are presented based on a model of frustule division applicable to the Monoraphidineae. Bacterial mucilage may also occur over the diatom mucilage, but the extent of each could not be assessed because of their morphological similarity when mixed.
Article
Data on the effect of substratum critical surface tension on the rate of microbiological attachment to solid surfaces immersed in natural seawater are considered. Apparently conflicting trends in the data are examined in terms of the surface energetics of adsorption of molecular organic “conditioning films” to the solid surface. A model based on interfacial tension and the work of Good and co-workers is presented which accounts for the presence of both types of behavior and points out that experimental results are extremely sensitive to the details of initial surface preparation.
Article
Extracellular polymeric substance (EPS) secretion was examined in the stalked marine diatom Achnanthes longipes Ag. in defined medium. This common biofouling diatom exhibited an absolute requirement for bromide for stalk production and substratum attachment, whereas elevated iodide concentrations in the growth medium inhibited stalk formation and adhesion. Varying EPS morphologtes resulted from altering bromide and iodide levels: pads, stalk-pads, stalks, and no EPS. Cells showed no differences in growth with bromide or iodide concentrations, indicating that they were not physiologically stressed under conditions that impaired EPS secretion. Cells grown in elevated iodide secreted significantly more soluble extracellular carbohydrate into the medium, suggesting that the EPS was soluble and unable to be polymerized into a morphologically distinct gel. By replacing sulfate with methionine, the diatom lost its ability to form stalks even in the presence of bromide, indicating that free sulphate may be required for proper cross-linking of stalk polymers. Lotus-FITC, a fluorescent-tagged lectin, preferentially labeled the EPS and, thus, was used to visualize and quantify EPS secretion along a bromide gradient in conjunction with an image analysis system. This technique demonstrated a direct correlation between the amount of bromide present in the medium and the specific EPS morphology formed.
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This chapter presents a framework for understanding the process of biofilm development on a surface and the consequences of the accumulation on the environment. It begins by describing biofilm development in terms of selected fundamental rate processes and environmental parameters influencing their rate and extent. The physical, chemical, and biochemical properties of the biofilm that determine the influence of the biofilm on its microenvironment are discussed in the chapter. The properties of the biofilm and its microenvironment lead to a discussion of the microbial ecology within the biofilm and the physiology of the organisms immobilized within it. The effects of the biofilm on its environment, both beneficial and detrimental, are presented. There are many other questions and concerns stated in this chapter regarding biofilm processes.
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Investigations on the adhesion of a diverse range of biological systems including proteins, tissues, microbes, algae and invertebrates all indicate that minimal long-term adhesion is associated with surfaces having initial surface tensions between 20 and 30 dynes/cm (mN/m), i.e. low energy surfaces. However, all surfaces rapidly become modified on immersion in natural waters through the adsorption of ‘conditioning films’, which may influence subsequent adhesive events associated with the permanent attachment of organisms. In this review the various methods which have been used to measure the strength of attachment of both micro- and macrofouling to surfaces will be outlined and results presented for substrata with a range of surface energies. Data will be presented which show that surface energy can elicit different responses in different organisms. For most organisms, minimal adhesion is associated with low surface energy. Silicone elastomers and fluoropolymers have received most attention regarding their potential use as foul release coatings. Results on the antifouling performance of these classes of materials will be discussed.
Article
A bubble contact angle method was used to determine interfacial free-energy characteristics of polystyrene substrata in the presence and absence of potential surface-conditioning proteins (bovine glycoprotein, bovine serum albumin, fatty acid-free bovine serum albumin), a bacterial culture supernatant, and a bacterial exopolymer. Clean petri dish substrata gave a contact angle of 90 degrees , but tissue culture dish substrata were more hydrophilic, giving an angle of 29 degrees or less. Bubble contact angles at the surfaces exposed to the macromolecular solutions varied with the composition and concentration of the solution. Modification by pronase enzymes of the conditioning effect of proteins depended on the nature of both the substratum and the protein, as well as the time of addition of the enzyme relative to the conditioning of the substratum. The effects of dissolved and substratum-adsorbed proteins on the attachment of Pseudomonas sp. strain NCMB 2021 to petri dishes and tissue culture dishes were consistent with changes in bubble contact angles (except when proteins were adsorbed to tissue culture dishes before attachment) as were alterations in protein-induced inhibition of bacterial attachment to petri dishes by treatment with pronase. Differences between the attachment of pseudomonads to petri dishes and tissue culture dishes suggested that different mechanisms of adhesion are involved at the surfaces of these two substrata.
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The role of bacteria in the development of algae on low-density vinyl was investigated. Unidentified bacterial contaminants in unialgal stock cultures of Phormidium faveolarum and Pleurochloris pyrenoidosa enhanced, by 1 to 2 orders of magnitude, colonization of vinyl by these algae, as determined by epifluorescence microscopy counts and chlorophyll a in extracts of colonized vinyl. Colonization by bacteria always preceded that by algae. Scanning electron microscopy of the colonized Phormidium-bacteria mixture revealed the presence of a slime matrix engulfing both bacteria and algae that may have facilitated algal attachment. Slime was not evident in the Pleurochloris-bacteria mixture, suggesting that the attachment mechanisms differ for the two algae.
The effects of adsorbed marine organics on microbial fouling
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