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Effects of bromide and iodide on stalk secretion in the biofouling diatom Achnanthes longipes (Bacillariophyceae)
Abstract
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.
... Quantifying iodine accumulation and growth of microalgae in relation to external iodine concentration is of special relevance for a better understanding on iodine and iodine compounds trophic transfer from phytoplankton in marine ecosystems as well as in marine aquaculture food chains. Several studies looked at the effect of iodide and/or iodate on the growth rate of phytoplankton species (Sugawara and Terada1967; Fuse et al. 1989, Johnson et al. 1995, Imai et al. 2004 Zheng et al. 2005; Iwamoto and Shiraiwa 2012). In some cases, a negative effect was observed, in some cases a positive effect was observed, and in some cases no effect was observed of iodide and/or iodate concentration on growth rate. ...
... In some cases, a negative effect was observed, in some cases a positive effect was observed, and in some cases no effect was observed of iodide and/or iodate concentration on growth rate. In many cases, only one concentration of either iodide or iodate was tested (Sugawara and Terada 1967; Johnson et al. 1995; Imai et al. 2004), or only low concentrations (Sugawara and Terada 1967; Imai et al. 2004) or only high concentrations (Zheng et al. 2005; Iwamoto and Shiraiwa 2012) were tested. In the present study, we cultivated marine microalgae at a wide range of concentrations of dissolved inorganic iodine in order to evaluate its impact on growth rate and to assess whether it is required for growth. ...
... At this concentration lipid accumulation may have been a response to stressful conditions, as has been described for Dunaliella in response to nutrient limitation or salt stress (El-Baky et al. 2004; Chen et al. 2011). Two studies reported an increase in extracellular polymeric substances (EPS) of diatoms as a result of I − addition, but it is not clear how this was related to the intracellular carbohydrate metabolism (Johnson et al. 1995; Zheng et al. 2005). No conclusion on any effect of iodine treatments on lipid metabolism could be drawn from the fatty acid profiles of the microalgae investigated in the Author's personal copy 107 Page 16 of 19 present study. ...
Marine phytoplankton have been found to be involved in the biogeochemical cycle of iodine in the ocean. However, the role of iodine in the metabolism of marine microalgae has hardly been studied and whether iodine is an element required for growth is not known. In this study, three species of marine microalgae were grown in batch cultures at various concentrations of iodide (I−) or iodate (IO3−) in order to evaluate their effect on growth rate and biochemical composition. Changes in inorganic iodine concentrations in the culture medium were also determined. Growth rate was not affected by external inorganic iodine concentration in cultures of Dunaliella salina and Tisochrysis lutea. In cultures of Phaeodactylum tricornutum, growth was inhibited at 2500 µM IO3−. No clear effects of I− or IO3− were observed on biochemical composition, except for the particulate iodine content of the microalgae, which increased with increasing dissolved iodine concentration. Results of dissolved inorganic iodine measurements indicated that IO3− was reduced to I− during the exponential growth phase of microalgae cultures, under both natural and higher IO3− concentrations. Iodine balance calculations showed that the amount of disappeared IO3− was higher than the amount of I− produced in several cultures and that this discrepancy could not be explained by the formation of particulate iodine. I incorporation rates into biomass were low compared to I− production rates. We conclude that although iodine is clearly taken up from the external medium and it is transformed by microalgae, it seems unlikely that it is an element required for growth or that it plays an essential role in microalgal metabolism.
... We propose that the origin of the released HOBr and HOI by diatoms is from an extracellular BrPO, residing in the apoplast, the space between the cell membrane and silicified frustule. The process of stalk assembly and adhesion by the temperate benthic diatom A. longipes requires bromide, and the oxidative phenolic crosslinking that occurs is thought to be catalyzed by an extracellular peroxidase, possibly a BrPO (Johnson et al. 1995; Vreeland and Epstein 1996). This species did test positive for the bromination and iodination of PR using the in situ assay (Table 2), thus strongly indicating the presence of an extracellular BrPO. ...
... Based on the in situ incubation assays, it appears that S. glacialis contains an IPO. A. longipes, T. pseudonona, and T. oceanica tested positive for BrPO in our assay, the latter being a warm-water strain. Our data supports the finding of a bromide-sensitive external peroxidase active in stalk formation of A. longipes (Johnson et al. 1995; Vreeland and Epstein 1996). The finding of activity in T. oceanica is significant in the context of bromoform production in warm water (see below). ...
An in situ incubation assay measuring the bromination and iodination of phenol red was developed to detect the release of reactive bromine and iodine (primarily hypobromous acid (HOBr) and hypoiodous acid (HOI), respectively) from a putative extracellular bromoperoxidase of marine diatoms. Six of 11 species showed significant release compared to controls. Polar species were particularly active, releasing 0.6-180 fmol HOBr cell21 h21 (0.04-1.8 mmol HOBr (mg total chlorophyll)21 h21; at the seawater bromide concentration, 840 mmol L21) and 1.9-271 fmol HOI cell21 h21 (0.02-2.7 mmol HOI (mg total chlorophyll)21 h21, at 100 mmol L21 iodide). Porosira glacialis consistently showed the highest rates of release. Several temperate diatoms, including Achnanthes cf longipes, known to have a bromide-sensitive peroxidase involved in stalk formation, and warm- water species also showed the ability to release reactive bromine and iodine. This release was influenced by light, temperature, bromide (and iodide) concentration, H2O2 concentration, and pH. The rate of HOBr release by polar diatoms was much greater than bromoform emissions measured by others from laboratory cultures and sea- ice algae in the field. This indicates that most of the HOBr released may react with dissolved organic matter (DOM) to form nonvolatile bromine organics. Some fraction of diatom-produced HOBr and HOI may also form volatile Br2 and I2, which could transfer to the polar troposphere. The reaction of diatom-released reactive bromine and iodine with seawater DOM may represent the major mechanism in the formation of oceanic polybromo- and polyiodo-methanes.
... gest that similar adhesion mechanisms may be involved in both macroalgae and microalgae. For example , because bromide is required for stalk assembly and adhesion by the diatom Achnanthes longipes, a bromoperoxidase may be involved (Johnson et al. 1995, Wustman et al. 1997). Because carbohydratecontaining adhesive mucilage is involved in phytoplankton aggregation (Passow and Alldredge 1995), a similar oxidase-activated mechanism might cause aggregation in benthic phytoplankton (Waite et al. 1997). ...
... Secreted adhesive precursors, especially the type of carbohydrate, do differ between motile diatoms and algal propagules (see Table 1). However, peroxidase-mediated assembly of adhesive is a possible mechanism in motile diatoms as well as in other algae (see Johnson et al. 1995). Differences in initial and secondary adhesion in algal propagules appear to include differences in proportions of precursors and the degree of crosslinking in the adhesive mucilage , as well as in possible differences in the nature of precursors. ...
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... Rost et al. [39] found similar trends in Sierra Nevada streams. The stalk of D. geminata is primarily sulphated polysaccharide [40]; therefore, sulphur limitation may inhibit stalk formation as observed in the stalkforming marine diatom Achnanthes longipes C. Agardh [41]. The presence of D. geminata in Norway was associated with a minimum sulphate concentration of 2.5 mg l −1 . ...
Didymosphenia geminata (Lyngbye) M. Schmidt is a stalked freshwater diatom that is expanding its range globally. In some rivers, D. geminata forms thick and expansive polysaccharide-dominated mats. Like other stalked diatoms, D. geminata cells attach to the substratum with a pad of adhesive extracellular polymeric substance. Research on D. geminata and other diatoms suggests that bacterial biofilm composition may contribute to successful attachment. The aim of this study was to investigate the composition and role of bacterial biofilm communities in D. geminata attachment and survival. Bacterial biofilms were collected at four sites in the main stem of a river (containing D. geminata) and in four tributaries (free of D. geminata). Samples were characterised using automated rRNA intergenic spacer analysis and high-throughput sequencing (HTS). Mat-associated bacteria were isolated and their effect on the early establishment of D. geminata cells assessed using co-culturing experiments. ARISA and HTS data showed differences in bacterial communities between samples with and without D. geminata at two of the four sites. Samples with D. geminata had a higher relative abundance of Sphingobacteria (p < 0.01) and variability in community composition was reduced. Analysis of the 76 bacteria isolated from the mat revealed 12 different strains representing 8 genera. Co-culturing of a Carnobacterium sp. with D. geminata reduced survival (p < 0.001) and attachment (p < 0.001) of D. geminata. Attachment was enhanced by Micrococcus sp. and Pseudomonas sp. (p < 0.001 and p < 0.01, respectively). These data provide evidence that bacteria play a role in the initial attachment and on-going survival of D. geminata, and may partly explain observed distribution patterns.
... Adhesion usually requires an oxidase mediated polymerisation of quinine (Vreeland et al., 1998; Hellio et al., 2000a). There are some common adhesion mechanisms among micro and macroalgae, such as the involvement of bromide for stalk assembly and adhesion (Johnson et al., 1995; Wustman et al., 1997; Passow and Alldredge, 1995; Waite et al., 1997) or of vanadium for the cross-linking of polyphenols to extracellular carbohydrate fibers (Vreeland and Epstein, 1996). Testing new AF compounds for their inhibitory activities towards various oxidases such as haloperoxidase , bromoperoxidase or similar oxidase-activated mechanisms could the next breakthrough for the development of fast, reliable, targeted and nonexpensive anti-algal assays. ...
Human impacts on coastal waters, through eutrophication and overfishing, associated with the global change phenomenon are leading to a proliferation of both micro- and macroalgae. Algae can settle and develop on a wide range of surfaces including both natural and man-made structures. They are fast colonisers and can out-compete numerous species. The fixation of marine organisms on immersed man-made structures is responsible for major economic costs and the recent recrudescence of algae in the environment might increase the fouling phenomenon observed: the resistance penalty for ships is known to be increased by 11% in presence of a light microalgal slime to 34% in case of colonisation by macroalgae (Schultz, 2007). The paints used nowadays often contain biocides, are non selective against target organisms and are not environmentally friendly. The development of new antifouling paints requires a better understanding of both the mechanisms of fixation and colonisation of the fouler organisms. This chapter focuses on the fixation of algae (both micro and macro), the damages they cause and the method of prevention currently used.
... Nevertheless, the option of studying D. geminata in a mixed algal community colonizing outdoor channels has proved successful, because, as has been pointed out previously (Whitton et al. 2009), the large size of D. geminata makes it an ideal model organism. Direct measurements of diatom stalk length have rarely been employed in previous studies on species–environment relationships, exceptions being studies on A. longipes (Johnson et al. 1995, Lewis et al. 2002). In the present experiments, our ability to accurately measure lengths of individual stalk segments was facilitated by the reaction of methylene blue with anionic polysaccharides providing contrast between the stalks and the non-staining polystyrene (Styrofoam TM ) substratum. ...
Blooms of the freshwater stalked diatom Didymosphenia geminata (Lyngb.) M. Schmidt in A. Schmidt typically occur in oligotrophic, unshaded streams and rivers. Observations that proliferations comprise primarily stalk material composed of extracellular polymeric substances (EPS) led us to ask whether or not the production of excessive EPS is favored under nutrient-limited, high-light conditions. We conducted experiments in outdoor flumes colonized by D. geminata using water from the oligotrophic, D. geminata–affected Waitaki River, South Island, New Zealand, to determine the relationship between D. geminata stalk length, cell division rates, and light intensity under ambient and nutrient-enriched conditions. Stalk lengths were measured in situ, and cell division rates were estimated as the frequency of dividing cells (FDC). FDC responded positively to increasing light intensity and to nutrient additions (N+P and P). Under ambient conditions, stalk length increased as light level increased except at low ambient light levels and temperature. Nutrient enrichment resulted in decreased stalk length and negative correlations with FDC, with this effect most evident under high light. Our results are consistent with the hypothesis that extensive stalk production in D. geminata occurs when cell division rates are nutrient limited and light levels are high. Thus, photosynthetically driven EPS production in the form of stalks, under nutrient-limited conditions, may explain the development of very high biomass in this species in oligotrophic rivers. The responses of FDC and stalk length under nutrient-replete conditions are also consistent with occurrences of D. geminata as a nondominant component of mixed periphyton communities in high-nutrient streams.
... The dominant diatom species in Tarraleah No. 1 Canal is Gomphonema, a raphid diatom with cells 35 µm long and 6 µm wide (Fig. 1a). Gomphonema secretes a mucous stalk which pushes the cells away from the wall (Fig. 1b) towards better light and nutrient conditions [9]. The stalks observed from the fouling at Tarraleah are hundreds of microns long, tens of times the size of the cell itself. ...
Freshwater biofilms are currently being studied to determine their effect on the capacity of hydroelectric power scheme canals and the structure of their turbulent wall layers. Mean velocity boundary layer profiles and total drag measurements have been conducted in a purpose built recirculating water tunnel on freshwater biofilms grown in a hydroelectric canal. Two different fouled surfaces were compared with a smooth painted surface to determine the effects of the physical characteristics of a biofilm on skin friction drag. A 310% increase in local skin friction coefficient was measured for a biofilm dominated by long filamentous algae streamers, and a 50% increase was measured for a biofilm dominated by a low-form gelatinous diatom.
... The pad then tears in half, producing the 'collar' adhered to the cell, additional to the adhesive pad on the substrate, after which the shaft is secreted from the raphe binding the two, thus forming the stalk (Figure 11e,f). In ideal growth conditions, the stalk can grow to a length of 500 mm (Johnson et al. 1995). Once attached via a stalk, a cell may divide several times, forming a large stack (ie colony) of cells adhered to a single adhesive stalk. ...
Diatoms are a major component of microbial slimes that develop on man-made surfaces placed in the marine environment. Toxic antifouling paints, as well as environmentally friendly, fouling-release coatings, tend to be effective against most fouling organisms, yet fail badly to diatom slimes. Biofouling diatoms have been found to tenaciously adhere to and colonise even the most resistant of artificial surfaces. This review covers the basic biology of fouling marine diatoms, their mechanisms of adhesion and the nature of their adhesives, as well as documenting the various approaches that have been utilised to understand the formation and maintenance of diatom biofouling layers.
Diatoms are an incredibly diverse group of microalgae that are primarily characterized by their highly ornamented siliceous cell wall. Diatoms have long been a source of interest in the field of bioadhesion due to their ability to adhere and glide upon surfaces, as well as construct extracellular adhesive structures that can enable temporary or permanent adhesion to a surface. This chapter introduces the various adhesion and motility strategies employed by a number of benthic diatom species, describing the mechanisms that facilitate these processes. We review the chemical, molecular, and physical characterization of extracellular polymeric substances resident on the cell surface, as well as those secreted specifically for adhesion and motility from various structures in the cell wall. We highlight the significant work undertaken using atomic force microscopy to understand the nanomechanical properties of these adhesives, allowing sub-molecular structures to be identified that have allowed new insights into their role in enhancing diatom adhesion to surfaces even in high-energy aquatic environments. Finally we look at how new technological advances, such as the recent sequencing of several diatom genomes, together with an integrative research approach, will facilitate the further identification and characterization of diatom adhesives.
Submerged natural and artificial marine substrata can rapidly become covered by biofouling organisms, of which diatoms are the early algal colonisers. Licmophora flabellata is an estuarine stalk-forming diatom that strongly adheres to substrata via a compound-branching polysaccharide stalk. In the present study, the effects of light, nutrients, temperature and turbulence were examined in laboratory cultures to determine how they affected stalk formation and growth rates. Growth rates in multiwell plates were estimated using in vivo fluorescence in a plate reader. Low light intensities (50, 100 and 150 µmol photons m−2 s−1) produced no or poor growth, whereas growth rates of 0.24-0.42 divisions per day were achieved at 233 µmol photons m−2 s−1. High growth rates coincided with long stationary growth periods (21-36 days) and long branching stalks (800-3500 µm). N, P and Si nutrients had no effect on growth or stalks, whereas high turbulence (from an orbital shaker) reduced stalk length but not growth. The results call for species-specific approaches towards mitigating the impact of fouling diatoms.
This cooperative Augmentation Award for Science and Engineering Research Training has provided training for two doctoral students in several important areas of marine microalgal biofouling, including marine diatom mass culturing and adhesive isolation, biochemistry of adhesives, and laboratory experiments on the effects of substrate preconditioning on diatom adhesion. Students have gained significant experience through exchange between cooperating labs. This grant augmented research described in "parent" award #N000T4-94-1-0273. The overall goal of this research has been to provide a better understanding of the diatom portion of the biofouling process, to facilitate the development of more effective methods to control marine biofouling. We have identified bromide as an absolute requirement for the formation of the principal attachment organ for a common biofouling diatom, which provides a unique and powerful tool for initiating synchronous stalk production on a large scale and facilitating further extracellular adhesive biosynthesis, secretion and physiology research. Several monoclonal antibodies directed against the adhesive of Achnanthes were produced, allowing for effective isolation, localization and analysis of adhesive components. Detailed chemical characterization of antibody epitopes in adhesives from Achnanthes provides requisite information to determine the nature of the interactions responsible for assembly and function of the adhesives.
Many experiments utilize static immersion tests to evaluate the performance of ship hull coatings. These provide valuable data; however, they do not accurately represent the conditions both the hull and fouling organisms encounter while a ship is underway. This study investigated the effect of static and dynamic immersion on the adhesion and settlement of diatoms to one antifouling coating (BRA 640), four fouling-release coatings (Intersleek(®) 700, Intersleek(®) 900, Hempasil X3, and Dow Corning 3140) and one standard surface (Intergard(®) 240 Epoxy). Differences in community composition were observed between the static and dynamic treatments. Achnanthes longipes was present on all coatings under static immersion, but was not present under dynamic immersion. This was also found for diatoms in the genera Bacillaria and Gyrosigma. Melosira moniformis was the only diatom present under dynamic conditions, but not static conditions. Several common fouling diatom genera were present on panels regardless of treatment: Amphora, Cocconeis, Entomoneis Cylindrotheca, Licmophora, Navicula, Nitzschia, Plagiotropis, and Synedra. Biofilm adhesion, diatom abundance and diatom diversity were found to be significantly different between static and dynamic treatments; however, the difference was dependent on coating and sampling date. Several coatings (Epoxy, DC 3140 and IS 700) had significantly higher biofilm adhesion on dynamically treated panels on at least one of the four sampling dates, while all coatings had significantly higher diatom abundance on at least one sampling date. Diversity was significantly greater on static panels than dynamic panels for Epoxy, IS 700 and HX3 at least once during the sampling period. The results demonstrate how hydrodynamic stress will significantly influence the microfouling community. Dynamic immersion testing is required to fully understand how antifouling surfaces will respond to biofilm formation when subjected to the stresses experienced by a ship underway.
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.
The freshwater stalked diatom, Didymosphenia geminata, has increased its proliferation in new and native ranges with the potential for significant ecological impacts to streams
around the world. Uncertainty remains regarding the water chemistry in which D. geminata thrives despite recent advances in the understanding of its suitable physical habitat. Stream surveys were conducted in the
central and the northern Sierra Nevada, CA, USA, to determine whether D. geminata distribution patterns were related to water chemistry and bedrock geology. Surveys included measurements of physical, chemical,
and biological parameters from 50 stream reaches in 35 different streams. The water chemistry variable, percent Ca2+ (P<0.001) provided the best fit models (binary logistic regression AUC 0.84) for predicting the presence of D. geminata in Sierra Nevada streams. Other significant water chemistry predictors included the percent SO4
2− and Mg2+ concentrations. The bedrock geology variable, percent meta-sedimentary rock in a watershed (P<0.001), provided the best fit model (binary logistic regression AUC 0.77) for predicting the presence of D. geminata. This study further defines the environmental conditions in which D. geminata thrives, provides insight into D. geminata ecophsyiology, and will help refine current distribution and risk assessment models.
Keywords
Didymosphenia geminata
–Stalked diatoms–Water chemistry–Bedrock geology–Nuisance algal blooms
A programme of research was initiated to provide information on the efficacy of the antifouling agents Irgarol 1051™ and Sea-Nine 211™ to zygotes of the fucoid alga Fucus serratus Linnaeus. The development of methodologies that incorporated the use of image capture and analysis, which minimised the problems of subjectivity and bias that can be typical, are also described. The generation of macro-instructions allowed rapid generation and interpretation of accurate quantitative data. Emphasis was placed on the use of methodologies that did not rely on the subjective determination of spore germination. Consequently, affects due to the biocides were determined that, otherwise, would not have been realised through normal analytical routines.Zygotes were exposed, in static non-renewal systems, for 3 days, to a range of concentrations of biocide dissolved in seawater. Data for seven zygote parameters were recorded daily and values of percentage germination were calculated. From these data, NOEC values of 8 μg l−1 were calculated for both Sea-Nine 211 and Irgarol 1051. An EC50 of 19.4 μg l−1 was also determined for Sea-Nine 211. It is, therefore, suggested that F. serratus zygote germination and early development is unaffected by published environmental concentrations of these biocides. Additionally, it has been demonstrated that the image capture and analysis methodologies developed provide an invaluable tool for use in future bioassays.
Gomphonema, a freshwater diatom, is currently being studied to determine its effect on the capacity of hydroelectric canals and the structure of turbulent boundary layers. Gomphonema is the primary fouling organism present in Tarraleah No.1 Canal (operated by Hydro Tasmania) and was found to cause a 10% reduction in flow carrying capacity. Filamentous algae streamers up to 200mm long have also been observed in the canal. A recirculating water tunnel was used to measure the characteristics of the boundary layer flow over a 997mm x 597mm test plate covered with a biofilm grown in the field in an attempt to better understand the mechanisms for the increase in drag. Mean velocity profiles for the fouled test plate have been compared with results for a smooth test plate.
Here we introduce a combined experimental and descriptive approach (termed resurrection ecology) to reconstructing historical perturbations, pointing out how direct tests with sediments and hatched resting eggs complement the traditional descriptive calculation of microfossil fluxes. In the Keweenaw Waterway, a freshwater estuary off Lake Superior, turn-of-the-century copper mining impacted the resident biota. Remain fluxes document that diatom, rhizopod, and Bosmina production all declined during stamp sand discharges but recovered rapidly after World War II, moving above background levels due to developing eutrophication. In addition to biogenic silica, we discovered that bromine flux holds promise as an indicator of diatom production and confirmed that this element is present in several genera. Fluxes of Daphnia resting eggs also increased dramatically since the 1940s, dominated by a hybrid apparently produced from crosses between offshore and interior Waterway species, after channeling promoted greater mixing of water masses. Toxicity studies with sediments and Daphnia clones directly tested recovery of environments after cessation of mining activities. The studies document that increased concentrations and fluxes of copper in the Waterway during mining discharges were toxic to invertebrates. Once stamp sand discharges ceased,the biota recovered rapidly due to a combination of decreased copper cycling and organic complexation. Although sedimentation has returned to near-background conditions and surficial sediments in much of Portage Lake are no longer toxic, eutrophication and faunal exchange with Lake superior make it unlikely that the original zooplankton community composition will return to the Waterway system.
Diatoms produce diverse three-dimensional structures that, due to their exponential rate of growth, may be of use in the manufacture of components for nanotechnology as an alternative to present linear lithographic techniques. Vapor replacement of the silicon permits the conversion of diatom silica valves and other structures to metal/ceramics, with no loss of structure. The literature on diatom nanotechnology is reviewed, along with suggestions on how diatomists might enhance this emerging technology. There is a need for a systematics based catalog of parts (via genomics technologies), improved diatom culture techniques, better understanding of the mechanisms of diatom morphogenesis and motility, and genetic manipulation, mutagenesis, and selection, as via the chemostat-like compustat. Given the self-motility of raphid diatoms, they could form the basis for industrially useful nanobots.
The insoluble cell wall polymers of cultured spinach cells contained esterified ferulic acid at 2-5 mg g(-1) dry weight. Gibberellic acid (GA3, 10(-11)-10(-6) M) promoted the expansion of these cells and simultaneoulsy suppressed peroxidase secretion, reduced the activity of cellular phenylanine ammonia-lyase and favoured the accumulation of wall-esterified ferulate and of extracellular soluble phenolic aglycones. When growth was prevented with 0·7 M sorbitol, GA3 still evoked the phenolic and peroxidase effects. It is suggested that peroxidase restricts growth by rigidifying the cell wall in two ways: (a) covalently by catalysing the conversion of feruloyl side-chains into diferuloyl cross-links and (b) non-covalently by catalysing the conversion of soluble phenolics into hydrophobic quinones (or polymers). GA3 is hypothesised to prevent this rigidification by inhibiting peroxidase secretion.
Observations on the colonization of antifouling paints by diatoms have shown that a small number of tolerant species are usually involved. These species colonize as the toxin leaching rate declines following the initial peak values, and remain even after the onset of macrofouling. Colonization of toxic environments necessitates some form of resistance, whether intra or extracellular. In view of this, tolerant Amphora and Navicula species colonizing cuprous oxide paints and exposed to increasing concentrations of CuC12 were processed for transmission electron microscopy and analysed using an energy dispersive system. This enabled investigation of the ultrastructural effects coupled with intracellular copper localization. Ultrastructural examination revealed that copper had entered the cells and was located in either "polyphosphate" or "copper" bodies. The polyphosphate bodies, spherical in shape, and normally located within the cell vacuoles contained high concentrations of phosphorus in association with calcium, and in some, copper. The copper bodies, irregular in outline, and usually associated with membranes, contained high concentrations of sulphur with copper and calcium. The evidence suggests that these bodies are important structures in-maintaining low concentrations of free copper within the cells and thus reducing its toxic effects.
Cytological events immediately following plasmogamy in Durvillaea potatorum are described. Eggs contain several types of cytoplasmic vesicle differing in size and appearance. Histochemical tests and measurements are used to characterise and distinguish different types of vesicle containing phenolic compounds, lipids and polysaccharides. Within 2 min of plasmogamy, small phenolic vesicles located just below the egg membrane undergo mass synchronised exocytosis. The contents of these vesicles are discharged as phenolic bodies on the outside of the membrane. Secretion of phenolic bodies precedes secretion of the primary zygote wall by several minutes. Limited secretion of phenolics also occurs in unfertilised eggs. Peripheral phenolic vesicles are distinguishable from physodes, which also contain phenolic compounds but which are significantly larger and tend to be localised around the egg nucleus. The possible functional significance of the phenolic bodies is discussed. Coated pits and vesicles are common in zygotes, and their presence is evidence for endocytosis.
Ecological and Scanning electron microscope (S. E. M.) studies indicated that the diatomAmphora was an important constituent in the initial colonization of test panels coated with a copper antifouling composition.Amphora was also found as the dominant fouling diatom species on paint samples from “in-service” supertankers and yachts. Associated with the diatom was copious amounts of mucilaginous material, which often encapsulated the cells. Histochemical analysis of the mucilage indicates that it is predominantly polysaccharide in nature. Using the Transmission electron microscope (T. E. M.) and electron microscope cytochemistry the intracellular origin of the adhesive was investigated. T. E. M. and S. E. M. observations of acid-cleaned-cells indicate that the mucilage may be secreted through specialized regions of the frustule. Material isolated from antifouling panels was compared with laboratory culturedAmphora spp. for copper resistance and internal accumulation using TEMSCAN — X ray analytical equipment.
The cytochemical reactions of the attachment mucilage of 12 diatom genera (total 17 species) have been examined. These organisms are all found as members of fouling communities and, in some cases, are the dominant component. In every case the mucilages were found to be exclusively polysaccharide, except in Berkeleya rutilans where a low level of protein was also detected. All the polysaccharides contained anionic constituents, with carboxyl groups predominant in the pad-forming species and in early stages of attachment of the stalked species, whilst sulphated polysaccharides were more prevalent and in greater proportions in chain-forming and tube-dwelling species and in the stalks of Achnanthes and Licmophora. These stalks show distinct anatomical differences as well as differences in cytochemistry. The possible significance of the variations in cytochemistry are considered for the different growth forms.
Energy-dispersive X-ray microanalysis shows that the mucilage stalk of the diatom Achnanthes longipes contains calcium, magnesium, silicon, and other elements usually present in small amounts. Calcium and magnesium are probably present in the form of carbonates (high magnesian calcite). There appears to be more silicon towards the stalk collar than towards the part of the stalk which adheres to the substrate. This suggests that the deposition of silicon within the stalk could be related to intracellular deposition. The stalk also contains much sulphur. This may be attributed to sulphated polysaccharides, whose presence has already been demonstrated by means of cytochemical investigations.
Previously undescribed behaviour of the large (≈ 400 μm) motile diatom Gyrosigma balticum was observed in intact sediment cores from a non-tidal mudflat. Instead of lying flat against the sediment surface, the individual cells were found orientated with their long axes perpendicular to the sediment surface. Staining with toluidine blue indicated that the mechanism behind the erect position was a short (100–200 μm) mucilage tube produced at the lower end of the cell. It is suggested that the upright life-form may be common among epipelic diatoms. A diurnal/vertical rhythm into and out of the sediment was also observed. The peak of the oxygen profile in the Gyrosigma mat occurred 250–300 μm above the sediment surface, i.e. within the layer of upright cells.
This paper evaluates the utilisation of space by epibenthic diatom cells, as a response to environmental variations. The aggregation pattern of five species of epibenthic diatoms was quantified and compared to provide evidence for the significance of cell motility as an adaptive mechanism for space occupation and monopoly. The epibenthic diatoms included (1) non-mobile colonial species forming either fan-shaped (Synedra tabulata (Ag)Kz.) or arborescent (Gomphonema kamtschaticum var. californicum Grun.) colonies; (2) slow-moving (Cocconeis costata Greg, and Amphora pusio Cl.), and (3) fast-moving (Navicula direct a (W. Sm.) Ra.) non-colonial species. The aggregation pattern of S. tabulata did not vary significantly among six different light intensities manipulated in nature. The major patterns of aggregation were identified using analysis of covariance and dummy-variable regression. Highly mobile N. directa are significantly less aggregated than the four other diatom species. Non-mobile and slow-moving species show a similar, highly aggregated pattern. The occurrence of two patterns of spatial dispersion indicates that growth forms bear far-ranging ecological implications with respect to colonization strategies, immigration, and possibly impact by grazers. An integrated model of growth form characteristics, biological properties, and ecological implications is presented for epibenthic diatoms.
The elements in group 17 (VIlA) of the periodic table of elements-fluorine (F), chlorine (CI), bromine (Br), and iodine (I)-were designated by Berzelius as "halogens" (Greek hals, sea salt; gennao, I beget) because of their propensity to form salts. In this first of the two volumes of Bio chemistry of the Halogens, the biochemistry of the elemental halogens and inorganic halides is reviewed. Discovery, properties, and biochemistry of the elemental halogens are reviewed first (Chapter 1). This is followed by a review of the developments in the various areas of inorganic halide biochemistry (Chapters 2 through 5). The biochemistry of thyroid hor mones is considered in Chapter 6, while biohalogenation, an important link between inorganic and organic halogen biochemistry, is reviewed in Chapter 7. Chapter 8 covers the biochemistry of products produced by human-inspired halogenation, in particular, poly halogenated compounds that present environmental problems. In Chapter 9, the process is reversed and biodehalogenation is reviewed. In each subject, the attempt has been made to find an appropriate balance between depth and breadth of treatment, since a thorough, in depth review of this field would not be possible in a single volume. To provide readers not familiar with subjects with the necessary background to place subsequent discussions in perspective, brief historical develop ments of many of the topics are given.
Alterations in cell-wall structure and metabolism are closely coupled to the developmental processes of growth, differentiation, and morphogenesis. Although the structure and function of the cell wall have been studied extensively, relatively little attention has been devoted to the mechanisms by which a cell wall is initially assembled outside the plasma membrane. Understanding the steps and pattern in which various polymers are assembled into an extracellular structure will be helpful in elucidating a chemical and physical model of the cell wall. This developmental or inductive approach should complement that used by Albersheim, in which an existing cell wall is dissected with chemical and enzymatic techniques. From this, Albersheim’s group can deduce the chemical architecture of an already existing structure (Keegstra et al., 1973). Unfortunately, wall assembly in angiosperms is not amenable to biochemical experimentation, since most cases of initial wall construction occur within complex tissue masses and are difficult to isolate from other concurrent biochemical events. For example, in meristems, the construction of new cross-walls during telophase has been described cytologically, but to identify individual wall polymers and how they are linked to other polymers, as well as how the process of wall assembly is directed to only the sites of new plasma-membrane formation (i.e., the “end walls”), is difficult to approach.
Iodine is an essential nutrient for the growth of the marine brown alga Ectocarpus siliculosus, though filaments survive for at least 12 weeks in iodine-deficient media. Iodine is not replaceable by bromine at any of the concentrations tested. At least 1.5 × 10−3 μg at iodine/l is required for any appreciable vegetative growth, while 2.5 × 10−2 μg at/l is needed for the normal formation and maturation of plurilocular sporangia (Natural sea water contains about 4 × 10−1 μg at iodine/l). In 12-week cultures, 2 × 10−1 μg at iodine/l promotes .maximum growth, equivalent to 4 g dry weight per litre of medium. Concentrations up to one hundred times as high are tolerated without evident inhibitory effects.
Growth of embryos of Fucus edentatus varied with the amount of nitrogen, phosphorus, and iron added to sea-water. Rapid growth occurred with relatively low concentrations of these elements, and an added N: P ratio of 30: 1 did not retard development. Omission of added silicon did not affect growth, even though germanium was previously reported toxic. Growth and development in a synthetic medium was comparable to that in enriched seawater provided bromine was added to the latter. Boron was also found to be essential, and a deficiency resulted in moribund embryos during the four-week period of incubation.
In the wheat root, peroxidases and esterases specific for a-naphthyl esters of acetate, propionate and butyrate are concentrated in cell walls, particularly the outer wall of epidermal cells undergoing extension. In contrast esterases specific for β-naphthyl esters of propionate and butyrate were intra- cellular and concentrated in epidermal and outer root-cap cells of the wheat root. Both α-naphthyl and β-naphthyl esters of longer-chain fatty acids proved to be poor substrates. The esterases and peroxidases associated with the outer epidermal wall may well be involved in turnover of phenolic acids cross-linked to polysaccharides. In this regard, ferulic acid and diferulate were shown to be constituents of wheat-root cell walls. The distribution of these substances can also be inferred from autofluorescence. Treatment with a commercial pig-liver esterase was without effect on the auto- fluorescence of the root cell-walls. Culture filtrates from Gaeumannomyces graminis did remove significant amounts of autofluorescent wall material. These preparations contained α-naphthyl acetate esterase as well as many polysaccharide hydrolase activities.
Refractile inclusions characteristic of the vesicle cells of members of the Bonnemaisoniaceae fail to form if bromide is omitted from the culture medium. Electron microprobe analysis shows the localization of bromine in these cells. When grown in the presence of bromide, but not when grown in its absence, these organisms oxidize iodide to iodine; in Trailliella, this oxidation occurs at the vesicle cells.
In order to clarify the relationship between structure and properties, dynamic viscoelastic measurements and differential scanning calorimetry were carried out for kappa-carrageenan gels containing ammonium salts. Elastic modulus E′ of kappa-carrageenan gels as a function of the concentration of NH4F, NH4Cl, NH4Br or NH4I increased with increasing concentration of salt and then decreased. In the case of gels containing iodide ions, the peak of E′ increased and shifted to higher concentrations. This has been attributed to the rearrangement of kappa-carrageenan molecules towards a more stabilized structure in the presence of iodide ions. The endothermic peak temperatures accompanying gel-to-sol transitions shifted to higher temperature with increasing concentration of salt. This has been attributed to the shielding of the electrostatic repulsion of sulphate groups in kappa-carrageenan molecules by ammonium ions'as in the case of the addition of alkali metal or alkali earth metal ions or guanidinium ions. In both thermal and rheological properties, gels containing iodide ions showed different behaviour to those containing bromide, chloride or fluoride ions.
The red alga Polysiphonia urceolata (Rhodomelaceae, Ceramiales) shows a bromine requirement for optimal growth when cultivated in axenic culture. No influence of bromine on growth of Goniotrichum alsidii (Goniotrichaceae, Bangiales) was observed. Organically bound bromine (lanosol) could be utilized by Polysiphonia as a bromine source. Some correlation between iodide concentration and suitable bromide concentration in the medium was indicated.
Ahstract The production of soluble, '%-labeled organic material from H "C0,- by cultures and natural populations of marine phytoplankton has been examined with particular attention to cxperimcntal technique. Extracellular release is a normal f;mction of healthy cells, is closely related to photosynthetic rate, and is a minor component (up to 5 pg C-liter-'ah-') of total primary productivity in coastal waters. Time-course studies and chemical cell-fractionations indicate that newly synthesized organic "'C is distributed among various cell polymers and the extracellular medium from a rapidly labeled, soluble intracellular pool of small molecules. The rate of supply of carbon to this pool may determine the relative rate of release. Extra- cellular "C appearing during transient light shock may preferentially arise from rapidly mo- Ijilized polysaccharide and is not simply the result of cell lysis. The l&C
Adsorption of a “conditioning”; film precedes the development of communities typically dominated by diatom slimes, filamentous algae or invertebrates. The type and extent of fouling is often specific to a particular location, being influenced by water chemistry, eutrophication and whether any local control measures are employed. The zebra mussel, Dreissena polymorpha, and its rapid spread in North America, makes it probably the most economically important fouling organism in freshwaters at the present time. The types of fouling control measures in current use and future developments are discussed.
The ratio of the growth medium was varied in six steps from 0.4 to 100 in batch cultures of the marine diatoms Skeletonema costatum (Grev.) Cleve and Chaetoceros affinis var. willei (Gran) Hustedt. The influence of these changes on growth rate, assimilation ratio of nitrogen and phosphorus, production of cellular and extracellular carbohydrates, protein, cellular phosphorus and cell size was studied during exponential and stationary growth phase.A decrease in the growth rate from ≈ 1.7 to 1.1 div. day−1, and a decrease in the rate of uptake of nitrate from the growth medium, were observed at ratios in the medium over the range of 10 to 100. The content of phosphorus/cell was almost constant for the lowest ratios both in the exponential and stationary growth phase, and then decreased for both species with an increasing ratio. The cellular ratio is not constant, but changes in the direction of the composition of the medium. The range of the cellular ratios was from ≈ 2 to 59.Rapidly growing cells of both species produced relatively little carbohydrate while slow-growing cells produced relatively much more, and this production is influenced by the ratio of the medium. An increase in the ratio of the medium leads to a decrease in the ratio of cellular protein to carbohydrate in the exponential phase and an increase in the same ratio in the stationary phase. The major increase in cellular carbohydrate was due to an increase in the β-1,3 glucan content. The ratio of cellular carbohydrate to cellular phosphorus varied from 15 to 675 and this ratio is suggested as another useful indicator of the physiological state of marine diatoms.Particularly at high ratios, C. affinis produces large amounts of an extracellular polysaccharide, and under extreme P-deflciency this production is likely to constitute the main photosynthetic activity. S. costatum produced only small amounts of extracellular polysaccharides.The two species also show an important difference in the balance point — the value found being ≈ 12 for S. costatum and 24 for C. affinis i.e., S. costatum is likely to use more of the available phosphorus than C. affinis and is more able to divide and produce cellular carbohydrate when under N-limitation. The potential ecological significance of these findings is discussed.
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.
ALGAE are known to concentrate the element bromine, but, like chlorine, this may occur only as ballast1. The nature of accumulated bromine is uncertain. In several rhodophycean species, specialized cells, or ``bromuques'', have been recognized2, whereas chlorine is apparently accumulated in the vacuole. Large amounts of bromine have been shown to occur in organic combination with phenols in members of the Rhodomelaceae1-3.
It is widely accepted that marine phytoplankton lose appreciable photoassimilated carbon into seawater as organic compounds; the phenomenon is usually referred to as excretion. Two lines of evidence for excretion are found in the literature: measurements in field studies of "organic 14C" in productivity experiments and the appearance of organic matter in labora- tory culture filtrates. Laboratory experiments and a literature review lead to the suggestion that the evidence for excretion is marred by two procedural artifacts, inadequate assess- ment of control blanks in the "C field measurements and the results of cultural shock in laboratory studies. Evidence of extensive excretion by phytoplankton is not good.
The general arrangement of cytoplasmic organelles in Achnanthes subsessilis is similar to that of other pennate diatoms so far investigated. The central nucleus is surrounded by perinuclear Golgi bodies which are believed to produce vesicles containing stalk material. The stalk is composed of four layers, is secreted from the raphe and in this region is surrounded by a mucilaginous collar. At the point of attachment the stalk spreads out over the surface and the outer layer terminates. The stalk is composed of polysaccharide without any associated protein, and the centre is more sulphated than the periphery. The stalk raises the cell well above the boundary layer on an antifouling-treated surface, thus permitting its continued growth and multiplication.
Excretion from the marine diatom Chaetoceros affinis was investigated in batch cultures. The rates of release of carbohydrates and amino acids per cell were higher in rapidly growing cells than in stationary phase cells. However, because photosynthesis per cell decreased significantly during nutrient depletion, excretion constituted 58% of total photosynthesis in stationary cells compared to 10% during exponential growth. The most prominent extracellular amino acids in the exponential phase were aspartic acid, glutamic acid, serine, glutamine, glycine, alanine, valine and leucine. In the stationary phase arginine, asparagine, tyrosine and isoleucine were also produced. Carbohydrate, of which polysaccharide constituted >80%, was the most abundant extracellular component released.
DESTRUCTION of surface ozone in the Arctic environment during the spring is thought to be caused by photochemical reactions involving bromine compounds1. Berg et al.2 reported a pulse of bromine particles and gases in the Arctic lower atmosphere in spring, which may be responsible for this surface ozone destruction and for which biogenic sources have been hypothesized1–3. Here we report laboratory and in situ measurements which indicate that Arctic ice microalgae emit significant quantities of bromoform (CHBr3), which may be converted photochemically into active forms of bromine. Our estimates of total annual bromoform release indicate that polar ice algae might contribute globally significant amounts of organic bromine compounds, comparable with anthropogenic and macrophyte sources.
Bromoperoxidase from the marine green alga Penicillus capitatus is a soluble heme protein capable of catalyzing the peroxidation of a wide variety of organic and inorganic substrates. Bromoperoxidase at neutral pH has high specific activity for bromide and iodide oxidations. The Vmax values for bromide and iodide oxidations are 5900 and 35000 mol min-1 (mol of BPO)-1, respectively. At acidic pH, bromoperoxidase catalyzes the oxidation of chloride ion. Radiolabeling experiments demonstrate the ability of the enzyme to catalyze chloride ion oxidation and insertion of chloride into the halide acceptor molecule monochlorodimedone. The rates of several reactions catalyzed by bromoperoxidase are strongly enhanced by bromide and chloride ions. The rate of molecular bromine formation is nearly twice the rate of bromination of monochlorodimedone. Thus, bromination is proposed to occur via molecular bromine rather than via an enzyme-bound intermediate. The pH-rate profiles for bromide and chloride ion oxidations provide new insights for possible control mechanisms for halide ion peroxidations.
A particulate enzyme displaying peroxidase activity has been extracted from the red alga Cystoclonium purpureum (Huds.) Batt. The enzyme preparation was shown to contain ferri-protoporphyrin IX through its formation of formic acid hemochromogen with absorption maxima at 399, 402, 555 and 600 nm. The preparation catalyses the formation of 3-bromo-p-hydroxybenzyl alcohol from p-hydroxybenzyl alcohol in the presence of H2O2 and NaBr at pH = 5.4. The formation of 3-bromo-p-hydroxybenzyl alcohol was measured by gas chromato-graphy-mass spectrometry. At pH = 6.7, 4,5-di-hydroxybenzyl alcohol was formed. Addition of homogentisic acid stimulated the formation of dihydroxybenzyl alcohol and suppressed the brominating reaction. Iodide inhibits the enzyme. The results are consistent with a two-site model of the enzyme.
The nutrition of the free-living phase of Conchocelis of P. tenera was studied axenically. Conch-ocelis preferred NO3, as nitrogen source. Urea and NH4 in low concentration, asparagine, and lysine were very good N sources. Several other amino acids were also utilized but growth was less abundant. Inorganic and organic phosphates were utilized; they were required at relatively low concentrations. Glycerophosphate gave excellent growth in a comparatively wide range of concentrations (0.1-5 mg P %). The optimal Ca concentration was 10-100 mg %. Needs for boron, manganese, zinc, strontium, rubidium, lithium, and iodine were demonstrated. The iodine effect was remarkable (peak growth with 1μg %); the effective concentration range was very narrow. Iron, cobalt, and bromine seemed to be adequately supplied as impurities of the macro-nutrients. A modified artificial medium (ASP12I) for the Conchocelis phase is presented.
Some red algae in axenic culture have been cultivated with different additions of iodine and bromine. Polysiphonia urceolata appeared to have an absolute demand for iodine. Additions could be made either as organically bound iodine or as inorganic iodine. A linear correlation between amount of added iodide and growth was found for iodide concentrations from 1 μmol up to at least 8 μmμmumol per 1. Nemalion proved to be indifferent to iodide additions, while Goniotrichum elegans was inhibited by concentrations higher than 0.4 μumol per 1, which corresponds to that of natural seawater.
High additions of iodine generally inhibited growth of nonaxenic algae. Acrochaetium made an exception, being stimulated by 4 μumol per I.
Bromine in the same concentration as that of seawater, viz. 814.3 μmol pa 1 inhibited growth of most species, but amounts smaller than 50 μumol had in some experiments a slightly increasing effect. Bromine seems, however, not to play an essential part in the metabolism of Polysiphonia urceolata.
Three marine brown algae have been cultivated with different additions of iodine and bromine in bacteria-free cultures. Ectocarpus jasciculatus appeared to have an absolute demand for iodine and was inhibited by a concentration of 64 μmol of KJ per 1. Lithosiphon pusillus had the best growth in the highest concentration tested (64 μmol/1) but there was always some growth in the series without iodine. Additions could be made either as inorganic iodine or as organically bound iodine. Additions of KJ to a culture medium consisting of vitamin-free Asp 6 F with B12 (1 μg/1) and kinetin (20 μmol/1) remarkably increased the growth of the zoospores of Pylaiella litoralis.
Lithosiphon pusilius proved to be indifferent to bromide additions in media containing KJ. In media lacking KJ addition of 1 μmol of KBr per 1 is stimulating but higher concentrations of KBr are inhibiting. The inhibiting effect is overcome by iodide addition.
Abstract Both the two major structural cell wall glycoproteins and the soluble excreted glycoproteins of Chlamydomonas reinhardii Levine WT II/32 contain low levels (approx. 1–4%) of sugar O-sulphate esters, asymmetrically distributed within the molecules. Preliminary characterization of their structure is described through [35S] sulphate labelling experiments. The function of the sulphated glycoproteins is discussed in terms of their structural role and their water retaining properties.
The halogens—chlorine, bromine and iodine—play an important, role in the biochemical processes of marine red algae. Recent studies show that various species from at least 5 orders of the Rhodophyta possess the unique ability to synthesize organic halogen-containing compounds which are derived from seawater components. A variety of substances have been reported, with various structures from simple aliphatic halo-ketones and brominated phenols to more sophisticated mono-, sesqui- and diterpenes. While the biological functions of these compounds are not clearly understood, they appear to provide environmental advantage, probably involving predator avoidance responses and microflora antibiosis.
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.
Diatoms isolated from mucilage blooms which emerged in the Adriatic Sea during summer 1988, were put in culture and then later, identified as Amphora coffeaeformis var. perpusilla (GRUN.) Cleve. Experiments of growth in orthophosphate and nitrate enrichment led to noticeable variations in the mucilage production. In this paper we propose a benthonic origin for the Adriatic mucilages, due to the presence of considerably more nitrates rather than phosphates.
The chemical composition of cells of Chaetoceros affinis var. willei (Gran) Hustedt grown in batch culture was markedly influenced by the concentration of nutrients in the medium. In the logarithmic growth phase the content of cellular glucan was relatively low, but in the stationary phase the glucan content showed a rapid increase which seemed to coincide with the depletion of nitrate from the medium. This led to very pronounced variations in the ratio of protein to carbohydrate. This ratio can easily be determined and seems to be a sensitive and convenient parameter for characterizing the physiological state of the diatom cells.In the stationary phase the alga also produced considerable amounts of an extracellular polysaccharide, particularly when grown in a medium with a high proportion of nitrate to phosphate.