MICROBIOLOGICAL CHARACTERIZATION OF A SULFIDE-RICH GROUNDWATER ECOSYSTEM

Movile Cave, recently discovered in southern Romania, contains sulfide -rich thermal waters in submerged passages, as well as isolated air po ckets. The water surfaces within the air pockets are covered by substa ntial microbial biofilms, while the air bells contain an abundant and diverse community of terrestrial and aquatic animal species. Based on the results of dehydrogenase activity, fecal streptococci counts, and stable carbon isotope ratios, we propose that the cave community is bi ologically isolated and receives little, if any, organic carbon inputs from the surface environment. Several sulfide-oxidizing chemoautotrop hic bacteria were isolated from the cave waters. One putative Thiospha era sp. strain, LV-43, was further characterized. The presence and hig h level activity of RuBisCO was clearly demonstrated in this strain.