Characterization of Bacterial Endosymbionts That Mediate an Organohalogen Cycle in Marine Sponges
Although organohalide compounds are typically considered to be anthropogenic compounds of industrial origin, they have their counterpart in several thousands of naturally occurring biogenic and geogenic organohalides. A particularly interesting source of organohalide compounds are the marine sponges that produce a vast array of bioactive compounds as secondary metabolites, including halogenated compounds. 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. This association between host sponge and associated microbiota may represent an ancient symbiotic or commensal relationship and we postulate that this association is at least partially driven by organohalogen chemistry of the sponge animal. Sponges date back >600 million years and have most likely produced antifouling and antipredatory compounds for much of this time, suggesting that the association with dehalogenating bacteria is ancient.
We have demonstrated that anaerobic organohalogen-respiring bacterial symbionts appear to be widespread in different sponge species. A novel bacterial species, Desulfoluna spongiiphila, and its close relatives may be responsible for reductive dehalogenation in geographically widely distributed sponges. Here, our objective is to gain an understanding of this “organohalide-driven” microbe-sponge symbiotic association, elucidating the interactions and feedbacks between biogeochemical activity (organohalide cycling) and microbial community structure and dynamics. Our overall hypothesis is that dehalogenating bacteria related to Desulfoluna spongiiphila are cosmopolitan and form stable populations within the sponge animal that function in the cycling of organohalide compounds. In our current work we aim to: 1) Characterize the diversity and specificity of dehalogenating Desulfoluna symbionts; 2) Determine whether anaerobic debrominating bacteria form stable or dynamic populations within the sponge animal; and 3) Elucidate the in vivo activity of sponge-associated dehalogenating bacteria.
Isabel Gray: Marine sponge associated dehalogenating microbes and compound specific isotope analysis of brominated phenols.
Collaborators: Ivonne Nijenhuis, Hans Richnow 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.
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. 59:2133-2139.