Article

Low densities of epiphytic bacteria from the marine alga Ulva australis inhibit settlement of fouling organisms.

School of Biotechnology and Biomolecular Sciences and Centre for Marine Bio-innovation, Biological Sciences Building, University of New South Wales, Sydney, NSW 2052, Australia.
Applied and Environmental Microbiology (Impact Factor: 3.95). 01/2008; 73(24):7844-52. DOI: 10.1128/AEM.01543-07
Source: PubMed

ABSTRACT Bacteria that produce inhibitory compounds on the surface of marine algae are thought to contribute to the defense of the host plant against colonization of fouling organisms. However, the number of bacterial cells necessary to defend against fouling on the plant surface is not known. Pseudoalteromonas tunicata and Phaeobacter sp. strain 2.10 (formerly Roseobacter gallaeciensis) are marine bacteria often found in association with the alga Ulva australis and produce a range of extracellular inhibitory compounds against common fouling organisms. P. tunicata and Phaeobacter sp. strain 2.10 biofilms with cell densities ranging from 10(2) to 10(8) cells cm(-2) were established on polystyrene petri dishes. Attachment and settlement assays were performed with marine fungi (uncharacterized isolates from U. australis), marine bacteria (Pseudoalteromonas gracilis, Alteromonas sp., and Cellulophaga fucicola), invertebrate larvae (Bugula neritina), and algal spores (Polysiphonia sp.) and gametes (U. australis). Remarkably low cell densities (10(2) to 10(3) cells cm(-2)) of P. tunicata were effective in preventing settlement of algal spores and marine fungi in petri dishes. P. tunicata also prevented settlement of invertebrate larvae at densities of 10(4) to 10(5) cells cm(-2). Similarly, low cell densities (10(3) to 10(4)cells cm(-2)) of Phaeobacter sp. strain 2.10 had antilarval and antibacterial activity. Previously, it has been shown that abundance of P. tunicata on marine eukaryotic hosts is low (<1 x 10(3) cells cm(-2)) (T. L. Skovhus et al., Appl. Environ. Microbiol. 70:2373-2382, 2004). Despite such low numbers of P. tunicata on U. australis in situ, our data suggest that P. tunicata and Phaeobacter sp. strain 2.10 are present in sufficient quantities on the plant to inhibit fouling organisms. This strongly supports the hypothesis that P. tunicata and Phaeobacter sp. strain 2.10 can play a role in defense against fouling on U. australis at cell densities that commonly occur in situ.

0 Followers
 · 
150 Views
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The accessory nidamental gland (ANG) of the female Hawaiian bobtail squid, Euprymna scolopes, houses a consortium of bacteria including members of the Flavobacteriales, Rhizobiales, and Verrucomicrobia but is dominated by members of the Roseobacter clade (Rhodobacterales) within the Alphaproteobacteria. These bacteria are deposited into the jelly coat of the squid's eggs, however, the function of the ANG and its bacterial symbionts has yet to be elucidated. In order to gain insight into this consortium and its potential role in host reproduction, we cultured 12 Rhodobacterales isolates from ANGs of sexually mature female squid and sequenced their genomes with Illumina sequencing technology. For taxonomic analyses, the ribosomal proteins of 79 genomes representing both roseobacters and non-roseobacters along with a separate MLSA analysis of 33 housekeeping genes from Roseobacter organisms placed all 12 isolates from the ANG within two groups of a single Roseobacter clade. Average nucelotide identity analysis suggests the ANG isolates represent three genera (Leisingera, Ruegeria, and Tateyamaria) comprised of seven putative species groups. All but one of the isolates contains a predicted Type VI secretion system, which has been shown to be important in secreting signaling and/or effector molecules in host-microbe associations and in bacteria-bacteria interactions. All sequenced genomes also show potential for secondary metabolite production, and are predicted to be involved with the production of acyl homoserine lactones (AHLs) and/or siderophores. An AHL bioassay confirmed AHL production in three tested isolates and from whole ANG homogenates. The dominant symbiont, Leisingera sp. ANG1, showed greater viability in iron-limiting conditions compared to other roseobacters, possibly due to higher levels of siderophore production. Future comparisons will try to elucidate novel metabolic pathways of the ANG symbionts to understand their putative role in host development.
    Frontiers in Microbiology 02/2015; 6:123. DOI:10.3389/fmicb.2015.00123 · 3.94 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Settlement of benthic marine invertebrate larvae often limits recruitment, influencing the structure and dynamics of natural populations as well as biofouling of marine infrastructure, ship hulls, and aquaculture operations. Certain microbial components of substratum biofilms influence settlement (e. g. bacteria, diatoms), but the importance of biofilm protozoa has been unknown. We tested for effects of ciliates by comparing settlement and survival of common fouling invertebrates among 3 biofilm conditions: no biofilm, a purely bacterial biofilm, and a biofilm of bacteria and ciliates. With an assemblage of 7 ciliates (from Hypotrichia, Haptoria, and Scuticociliatia), the serpulid polychaete Galeolaria caespitosa showed a 44 to 49% average reduction in settlement rate compared to the purely bacterial biofilm, and post-settlement mortality increased 7-fold to 34%. In contrast, settlement and survival of the bryozoan Bugula neritina were unaffected. With a partially different assemblage of 11 ciliates (from Hypotrichia, Stichotrichia, Haptoria, Colpodida, and Scuticociliatia), settlement of the serpulid Pomatoceros taeniata more than doubled, whereas that of the blue mussel Mytilus galloprovincialis was reduced by 54% compared to the purely bacterial biofilm. The results could not be explained by ciliates changing the total abundance of biofilm bacteria. We hypothesize that mechanisms could include direct interactions between larvae and ciliates (physical interactions, interference from ciliates' feeding currents, or responses to chemicals from ciliates), or indirect effects from ciliates altering the bacterial assemblage or its settlement cues. Such large and species-specific effects of ciliates on larval settlement and post-settlement mortality might impact invertebrate recruitment rates and species assemblages, especially because biofilm ciliates are highly variable over time and space. [GRAPHICS] .
    Marine Ecology Progress Series 03/2012; 449:1-12. DOI:10.3354/meps09638 · 2.64 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: In recent decade, seaweeds-associated microbial communities have been significantly evaluated for functional and chemical analyses. Such analyses let to conclude that seaweeds-associated microbial communities are highly diverse and rich sources of bioactive compounds of exceptional molecular structure. Extracting bioactive compounds from seaweed-associated microbial communities have been recently increased due to their broad-spectrum antimicrobial activities including antibacterial, antifungal, antiviral, anti-settlement, antiprotozoan, antiparasitic, and antitumor. These allelochemicals not only provide protection to host from other surrounding pelagic microorganisms, but also ensure their association with the host. Antimicrobial compounds from marine sources are promising and priority targets of biotechnological and pharmaceutical applications. This review describes the bioactive metabolites reported from seaweed-associated bacterial and fungal communities and illustrates their bioactivities. Biotechnological application of metagenomic approach for identifying novel bioactive metabolites is also dealt, in view of their future development as a strong tool to discover novel drug targets from seaweed-associated microbial communities.
    Applied Microbiology and Biotechnology 12/2014; 99(4). DOI:10.1007/s00253-014-6334-y · 3.81 Impact Factor

Full-text

Download
46 Downloads
Available from
May 27, 2014