Monday, 7 April 2014

Antifouling Bacteria in Sponges (Aplysina gerardogreeni)

Antifouling in marine environments as big business, but to date few microbes have been screened for this purpose, with fewer yielding extractable compounds. Marine microbes are exposed to myriad of environmental conditions and so are likely to hold many novel compounds, as well as being able too produce differing compounds in different culture conditions, and having a higher output of these compounds than could be gained from other sources (invertebrates, algae). Aguila-Ramirez et al. (2014) examined bacteria of the sponge Aplysina gerardogreeni (from a family well known for harbouring high numbers of associated bacteria) from the Gulf of California to assess its antifouling qualities.

Samples of 5g tissue were collected bimonthly from April for one year. Though the study does not specify from which region the samples were taken, and whether this was consistent across the study. Bacteria were isolated and cultured in soy broth, and tested for antifouling, antimicrobial, antimicroalgael properties. Bacteria that showed the greatest activity were also identified by partial sequencing of 16S rRNA gene fragments, and matched or compared to their closest recorded relative. This latter method is quite exclusionary, as some bacteria may in a  viable non culturable (VNBC) state, or just less efficient, in the soy cultures used – however as this study seems to ultimately be for commercial purposes, perhaps ease of access in regular mediums is part of the attraction.

The results showed Bacillus, Micrococcus, Paracoccus, Pseudobacter, Pseudovibrio, Psychrobacter, Staphylocuccus and Terribacillus to be present in A. gerardogreeni. These bacteria are reflective of it’s the varied habitats it is distributed in, including chemo-heterotrophs, aerobes or facultative anaerobes, with a fermentative or respiratory metabolism. Preforming functions from bioactive metabolites to protect A. geradogreeni from harmful microbes The latter being an antifouling function, which 50% of the bacteria were found to posses.

The most active isolates were closely related to the Bacillus species, which as Auigla-Ramirez pointed out falls in line with other such research involving this family found in different sources (nudibranch, microalage). Bacillus are widely studied for antimicrobial properties and produce a secondary metabolites synthesised n the ribosome which are especially effective against other members of the Bacillus family.

The temporal variation in activity ranged from the highest levels in February to the lowest in October, with Bacillus by far taking up the largest chunk of time. Other antifouling strains likely compensate for times of inactivity. The lack of activity in winter months indicate that the study has missed out cultures, likely due to VNBC, or/and that biofouling organisms associated with A. gerardogreeni are less prevalent at this time in the Gulf of California.

This study demonstrates some the rich treasure trove of tools waiting to be harvested from the ocean, and that those from sponges will hopefully help along antifouling technology. If there was a greater understanding of the likely symbiotic relationship between A. gerardogreeni and the bacteria which inhabit it, and the reasons fir such temporal variation (ecological or physiological), would most definitely help spur this research along. Use of metagenomics in this study would likely show many more antifoulant bacteria that that may no be able to be cultured, and perhaps change the temporal data gathered in this study. Especially following Deans latest post the A. gerardogreeni and the rest of the Aplysina family are likely more diverse than this study suggests.

Aguila-Ramírez, R. N., Hernández-Guerrero, C. J., González-Acosta, B., Id-Daoud, G., Hewitt, S., Pope, J., & Hellio, C. (2014). Antifouling activity of symbiotic bacteria from sponge< i> Aplysina gerardogreeni</i>. International Biodeterioration & Biodegradation, 90, 64-70.


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