SREL Reprint #1925

 

 

 

 

Biogeochemical Ecology of Thiothrix spp. in Underwater Limestone Caves

R. L. BRIGMON
Department of Physiological Sciences
University of Florida
Gainesville, Florida, USA

H. W. MARTIN
Biogeochemical Ecology Division
Savannah River Ecology Laboratory
University of Georgia
Aiken, South Carolina, USA


T. L. MORRIS
Cave Diving Section
National Speleological Society
Gainesville, Florida, USA


G. BITTON
Environmental Engineering Sciences Department
University of Florida
Gainesville, Florida, USA


S. G. ZAM
Department of Microbiology and Cell Science
University of Florida
Gainesville, Florida, USA

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.

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