Microbial ecology of a sulphidic and anoxic Blue Hole

Comunicación presentada en el The 6th International Congress on Extremophiles, September 17 - 21, 2006 Brest FranceDoñana National Park (Southwestern Spain) contains highly complex and diverse microbial communities. Within the park, there is a number of freshwater, shallow lagoons with a generally elevated iron concentration. On wind protected areas of the lagoons, Fe-rich films are formed on the water surface. This study analyzes the role of microorganisms on the formation of these Fe-rich films. Incubation of natural samples revealed that solar radiation is a factor to consider since it promotes film formation. Environmental measurements revealed a coupling of Fe and P in the studied samples. As well, differential composition in the phototrophic communities were observed in areas covered by the film and film-free zones. Cultures carried out under anaerobic conditions lead to enrichments composed by two major bacterial components and still mantaining the ability of forming Fe-rich films on the surface of the laboratory cultures. Using molecular techniques, we were able to identify the bacteria involved in the process. They are close relatives to the genera Enterobacter (Gamma-Proteobacteria) and Anaeroarcus (Firmicutes) and growing together under anaerobic conditions are able to form these films. Culturing this consortium under a variety of conditions we could deduce that the Fe-rich films were formed as a consequence of utilization of Fecomplexed with organic acids under anaerobic conditions. This study provides complementary information from environmental measurements and laboratory work to understand the role of microorganisms on the development of Fe-rich films on surface waters of Doñana National Park. The consequences of these findings are important in Fe and P biogeochemical cycling, with potential interest on the ability of these microorganisms in Fe sequestering from natural environments.Peer reviewe