"Never Waste A Good Crisis"

  • "...vast rings of coral-rock..."
    Wednesday, June 3, 2009 - 22:19

    morrisp

    “(…) every one must be struck with astonishment, when he first beholds one of these vast rings of coral-rock, often many leagues in diameter, here and there surmounted by a low verdant island with dazzling white shores, bathed on the outside by the foaming breakers of the ocean, and on the inside surrounding a calm expanse of water, which, from reflection, is of a bright but pale green colour. The naturalist will feel this astonishment more deeply after having examined the soft and almost gelatinous bodies of these apparently insignificant creatures, and when he knows that the solid reef increases only on the outer edge, which day and night is lashed by the breakers of an ocean never at rest."

    Darwin, Charles R. (1842)

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  • Hell's Aquarium...
    Sunday, May 31, 2009 - 23:16

    morrisp

    Found via Southern Fried Science:

     

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  • Stressed?
    Tuesday, May 26, 2009 - 21:52

    morrisp

    Porities compressa (found here)

    ~~~~~

    It definitely seems to be going around...(stress that is).  We're interested in temperature as a stressor - and how warmer temperatures influence pathogenicity...in corals (but we do live in coastal South Carolina - so it's quite possible to broaden this to just about everybody and everything soon).  Anyway - I came across an article today out of Rohwer's group - a nice study looking at the influences of stressors (pH, increased temperature, high nutrients, carbon) on the shift from mutualism to pathogensis.  Of specific interest to me was the observation (on page 9) that Vibrios, even without a significant change in abundance, led them to this hypothesis:  "...that subtle metabolic changes in these Vibrio spp., undetectable using exclusively ribosomal sequences, exert large effects on the disease potential of the coral holobiont."  Another interesting point brought up is found in the "Caveats" on page 10 of the manuscript  - especially the point about lack of true replication in metagenomic studies, and the need to 'move beyond these pseudo-replication style experiments.'

    This manuscript brings up alot of interesting questions...which is always a nice thing.   

    Here's the abstract:

    The coral holobiont is the community of metazoans, protists and microbes associated with scleractinian corals. Disruptions in these associations have been correlated with coral disease, but little is known about the series of events involved in the shift from mutualism to pathogenesis. To evaluate structural and functional changes in coral microbial communities, Porites compressa was exposed to four stressors:  increased temperature, elevated nutrients, dissolved organic carbon loading and reduced pH. Microbial metagenomic samples were collected and pyrosequenced.  Functional gene analysis demonstrated that stressors increased the abundance of microbial genes involved in virulence, stress resistance, sulfur and nitrogen metabolism, motility and chemotaxis, fatty acid and lipid utilization, and secondary metabolism.  Relative changes in taxonomy also demonstrated that coral-associated microbiota (Archaea, Bacteria, protists) shifted from a healthy-associated coral community (e.g. Cyanobacteria, Proteobacteria and the zooxanthellae Symbiodinium) to a community (e.g. Bacteriodetes, Fusobacteria and Fungi) of microbes often found on diseased corals. Additionally, low-abundance Vibrio spp. were found to significantly alter microbiome metabolism, suggesting that the contribution of a just a few members of a community can profoundly shift the health status of the coral holobiont.

    Full Citation:

    Thurber, R.V., D. Willner-Hall, B. Rodriguez-Mueller, C. Desnues, R.A. Edwards, F. Angly, E. Dinsdale, L. Kelly and F. Rohwer.  2009.  Metagenomic analysis of stressed coral holobionts.  Environmental Microbiology  doi:10.1111/j.1462-2920.2009.01935.x

      

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  • Sulfur-cycling in coral-associated bacteria
    Monday, May 25, 2009 - 21:30

    morrisp

    Well, we have indeed been neglectful of this space, haven't we?  Both Christina K and I attended the 2009 American Society for Microbiology General meeting in Philadelphia - and with the long holiday weekend, I'm just now thinking 'what was I up to?' (You know, that horrible Sunday evening feeling you sometimes get when you don't think about work all weekend?)  I have been thinking about work (some) - enough to at least see the latest publication just out by David Bourne and his colleagues.  I'm particularly curious about their article, focused on sulfur-cycling by coral-associated bacteria, since a doctoral candidate in my group (Nikole) is in the process of writing up a manuscript on biogeochemical cycling genes found in tissue and mucus-associated communities of Montastraea faveolata from the Caribbean (let's just say she's found alot of genes present her samples).  As a component of this published study, they isolated coral-associated bacteria on dimethylsulfoniopropionate (DMSP) and dimethyl sulfide (DMS) - an interesting approach I think.  Take a look for yourself. 

    Here's the abstract:

    Marine bacteria play a central role in the degradation of dimethylsulfoniopropionate (DMSP) to dimethyl sulfide (DMS) and acrylic acid, DMS being critical to cloud formation and thereby cooling effects on the climate. High concentrations of DMSP and DMS have been reported in scleractinian coral tissues although, to date, there have been no investigations into the influence of these organic sulfur compounds on coral-associated bacteria. Two coral species, Montipora aequituberculata and Acropora millepora, were sampled and their bacterial communities were characterized by both culture-dependent and molecular techniques. Four genera, Roseobacter, Spongiobacter, Vibrio, and Alteromonas, which were isolated on media with either DMSP or DMS as the sole carbon source, comprised the majority of clones retrieved from coral mucus and tissue 16S rRNA gene clone libraries. Clones affiliated with Roseobacter sp. constituted 28% of the M. aequituberculata tissue libraries, while 59% of the clones from the A. millepora libraries were affiliated with sequences related to the Spongiobacter genus. Vibrio spp. were commonly isolated from DMS and acrylic acid enrichments and were also present in 16S rRNA gene libraries from coral mucus, suggesting that under "normal" environmental conditions, they are a natural component of coral-associated communities. Genes homologous to dddD, and dddL, previously implicated in DMSP degradation, were also characterized from isolated strains, confirming that bacteria associated with corals have the potential to metabolize this sulfur compound when present in coral tissues. Our results demonstrate that DMSP, DMS, and acrylic acid potentially act as nutrient sources for coral-associated bacteria and that these sulfur compounds are likely to play a role in structuring bacterial communities in corals, with important consequences for the health of both corals and coral reef ecosystems.

     Full Citation:

    Raina, J.B., Tapiolas, D., Willis, B.L. and Bourne, D.G.  2009.  Coral-associated bacteria and their role in the biogeochemical cycling of sulfur.  Appl. Environ. Microbiol.  75:3492-3501.       

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  • Now, isn't this interesting?
    Tuesday, May 5, 2009 - 21:34

    morrisp
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