The marine environment is a particularly rich source of biogenic organohalides, which are produced by a diversity of marine organisms, including sponges. Marine sponges produce a vast array of bioactive compounds as secondary metabolites that include halogenated compounds, such as bromoindoles, bromopyrroles and bromophenolic derivatives. Sponges are filter-feeders and although prokaryotic microorganisms are a major component of the sponge diet, several studies indicate that complex, yet sponge-specific microbial communities thrive within sponge tissue. We postulate that this association between host sponge and associated microbiota is at least partially mediated by chemistry. We have previously demonstrated that the sponge Aplysina aerophoba which produces a brominated tryrosine derivative harbors anaerobic reductively dehalogenating bacteria. Our hypothesis is that dehalogenating bacteria form stable populations within the sponge animal that function in the cycling of organohalide compounds.
Using a combination of cultivation-based and molecular analyses we have shown that many species of temperate and tropical marine sponges harbor dehalogenating bacteria. Organobromine-rich sponges thus provide a specialized niche for organohalide-respiring microbes dehalogenating bacteria. We have also isolated a novel bacterial species, Desulfoluna spongiiphila, from Mediterranean sponges and demonstrated that this bacterium and its close relatives may be responsible for reductive dehalogenation in geographically widely distributed sponge species. This new bacterial species group is an excellent model system to study one of the earliest prokaryotic/eukaryotic endosymbioses and the possible origin of organohalogen respiration. Sponges date back more than 600 million year ago and have most likely produced organohalide compounds for this time, suggesting that the association with dehalogenating bacteria may be ancient. The presence of halogenated metabolites may thus have "recruited" microbes with the ability to utilize these as carbon sources or electron acceptors for growth. Whether dehalogenating bacteria provide any benefit to the sponge host remains to be seen. |
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Researchers: Isabel Horna Gray, Nora Lopez, Joanna Ahn and Kate Parisi
Publications
Ahn Y-B, Kerkhof LJ, Häggblom MM (2009) Desulfoluna spongiiphila sp. nov., a dehalogenating bacterium in the Desulfobacteraceae from the marine sponge Aplysina aerophoba. Int. J. System. Evol. Microbiol., in press.
Ahn Y-B, Rhee S-K, Fennell DE, Kerkhof LJ, Hentschel U, Häggblom MM (2003) Reductive dehalogenation of brominated phenolic compounds by microorganisms associated with the marine sponge Aplysina aerophoba. Appl. Environ. Microbiol. 69:4159-4166.
Funding: National Science Foundation
Collaborators:
Lee Kerkhof, Rutgers, Institute of Marine and Coastal Sciences
http://marine.rutgers.edu/main/IMCS-People-Details/People-Details-Lee-J.-Kerkhof.html
Ute Hentschel, University of Würzburg, Germany
http://www.zinf.uni-wuerzburg.de/young_investigator_groups/ag_hentschel/
