SREL Reprint #1925

Biogeochemical ecology of Thiothrix spp. in underwater limestone caves

R. L. Brigmon1, H. W. Martin2, T. L. Morris3, G. Bitton4, and S. G. Zam5

1Department of Physiological Sciences, University of Florida, Gainesville, Florida, USA
2Biogeochemical Ecology Division, Savannah River Ecology Laboratory, University of Georgia, Aiken, South Carolina, USA
3Cave Diving Section, National Speleological Society, Gainesville, Florida, USA
4Environmental Engineering Sciences Department, University of Florida, Gainesville, Florida, USA
5Department of Microbiology and Cell Science, University of Florida, Gainesville, Florida, USA

Abstract: Thiothrix spp., sulfide-oxidizing mixotrophic bacteria, were sampled from visible colonies in the Floridan aquifer in several underwater caves, sinkholes, and springs below the water table in North Florida. Bacteria samples were collected by cave divers certified by the National Speleological Society/Cave Diving Section. Sites sampled were ecological niches in the aquifer where visible colonies had a white slimy or filamentous appearance indicative of Thiothrix spp. Sterile sampling methods were adapted to the underwater cave setting. Bulk water samples for media preparation were collected by divers from bacteria sampling sites. Bacteria were isolated and cultured in growth media prepared with cave or spring water. Thiothrix spp. were identified by microbiological and immunological methods. Monoclonal antibodies specific for Thiothrix spp. were utilized in fluorescent antibody assays and enzyme-linked immunosorbent assays (ELISA). Thiothrix was found in six of eight underwater caves sampled. Three of these caves had no discernible waterflow at the time of sampling, indicating that Thiothrix in the Floridan aquifer does not necessarily require constantly flowing water. Most of the visible bacterial colonies that tested negative for Thiothrix were biofilms growing on limestone and iron oxyhydroxide substrates on the walls of clear-water and high-flow caves. The sulfur cycle in phreatic limestone conduits is described. The reactions and bacteria involved in the HS- cycle and pyrite cycle are discussed. Thiothrix generates sulfuric acid, which has the potential to dissolve limestone below the water table. Results of this study should contribute to a better understanding of the role of colorless sulfur bacteria in the development of porosity in carbonate rocks and microbial ecology in these karst aquifer settings.

Keywords: biogeochemistry, cave, ELISA, mixotrophy, phreatic, sulfide oxidation, sulfur bacteria, Thiothrix

SREL Reprint #1925

Brigmon, R.L., H.W. Martin, T.L. Morris, G. Bitton, and S.G. Zam. 1994. Biogeochemical ecology of Thiothrix spp. in underwater limestone caves. Geomicrobiology Journal 12:141-159. 

This information was provided by the University of Georgia's Savannah River Ecology Laboratory (srel.uga.edu).