Microbial Diversity in Acidic Anaerobic Sediments at the Geothermal Caviahue-Copahue System, Argentina

In this work we have examined the bacterial diversity from the hot spring sediment Agua del Limon (AL1) present at the geothermal Caviahue-Copahue system using a combination of molecular and cultivation techniques, with particular emphasis on indigenous anaerobic prokaryotes. Microorganisms involved in the iron (Acidithiobacillus ferrooxidans and Leptospirillum spp.) and sulphur (Acidithiobacillus spp., Thermotogales-like bacteria, Thiomonas sp., and Desulfurella sp.) cycles were identified in the clone library. Although no obvious sulfate-reducing bacteria were detected by culture-independent techniques, several isolates related to the mesophilic, spore-forming sulfate-reducer "Desulfobacillus acidavidus" strain CL4 were isolated at 30°C and 40°C. The 16S rRNA gene of another isolate showed 94% similarity to Desulfotomaculum thermobenzoicum. Sulfate-reducing enrichment cultures of the Copahue samples were also dominated by "Dsb. acidavidus" CL4.