HR: 17:30h
AN: H24C-07    [Abstracts]
TI: The Arsenic Cycle in Searles Lake, California: An Arsenic-Rich, Salt-Saturated Soda Lake. II. Isolation of Arsenic-Metabolizing Microbes.
AU: * Switzer Blum, J
EM: jsblum@usgs.gov
AF: US Geological Survey, 345 Middlefield Road, ms 480, Menlo Park, CA 94025 United States
AU: Hoeft, S E
EM: sehoeft@usgs.gov
AF: US Geological Survey, 345 Middlefield Road, ms 480, Menlo Park, CA 94025 United States
AU: Stolz, J F
EM: stolz@duq.edu
AF: Duquesne University, Dept. Biological Science, Pittsburgh, PA 15282 United States
AU: Langley, S
EM: slangley@uoguelph.ca.
AF: University of Guelph, Dept. Microbiology, Guelph, ONT NiG 2W1 Canada
AU: Beveridge, T J
EM: tjb@uoguelph.ca
AF: University of Guelph, Dept. Microbiology, Guelph, ONT NiG 2W1 Canada
AU: Kulp, T R
EM: trkulp@usgs.gov
AF: US Geological Survey, 345 Middlefield Road, ms 480, Menlo Park, CA 94025 United States
AU: Oremland, R S
EM: roremlan@usgs.gov
AF: US Geological Survey, 345 Middlefield Road, ms 480, Menlo Park, CA 94025 United States
AB: The motivation for isolating arsenic-metabolizing prokaryotes from Searles Lake was to characterize the physiology of microbes that can cope simultaneously with at least 3 environmental extremes: saturating salt concentration, high pH, and high dissolved inorganic arsenic. A secondary motivation was to find extremely halophilc Archaea that could respire As(V), as this has only been reported for the Crenarchaea. Enrichment cultures of arsenate [As(V)]-respirers were established by inoculating Searles Lake mud into an anaerobic, alkaline (pH = 9.8) artificial medium containing 346 g/L dissolved salts, with lactate as the electron donor and As(V) as the electron acceptor. After about 6 months of bi-weekly transfers, the enrichment was purified by serial dilution, with the highest growth-positive dilution tube exhibiting motile cells having uniform morphology (curved rods). This culture, strain SLAS-1, grew by oxidizing lactate to acetate plus carbon dioxide while reducing As(V) to arsenite [As(III)]. The doubling time was 48 hours at 346 g/L salinity, and nearly equivalent growth rates were observed over a salinity range of 200 to 346 g/l, with no growth evident below 200 g/L. The pH range was 8.5 to 10, with an optimum at 9.5. Strain SLAS-1 has an unusual motility that can be characterized as a "fish-like" swimming motion. Thin section electron micrographs revealed the presence of an internal cytoplasmic filament that runs the full length of the microorganism. We suggest that this filament may be involved in cellular motility. However, taxonomic classification of SLAS-1 made by 16S rRNA gene sequences aligned it in the order Haloanaerobacteriales of the Domain Bacteria. In a further effort to isolate haloalkaliphilic Archaea, a similar enrichment strategy was employed as above, but cell-wall antibiotics were added to the medium to discourage the growth of Bacteria. An enrichment culture, designated Serl-Ab, was established that oxidized lactate to acetate plus carbon dioxide. Preliminary evidence suggests that the culture consists of a lactate-oxidizing sulfate-reducer growing in synthrophy with a chemoautotrophic, sulfide-oxidizing As(V)-respirer. Terminal restriction length polymorphism analysis has indicated the presence of both bacterial and archaeal components in the Serl-Ab enrichment, although it is not yet known which is responsible for the observed As(V)-reduction and sulfate-reduction. Efforts are ongoing to resolve Serl-Ab by using classical isolation procedures for a heterotrophic sulfate reducer and an autotrophic As(V)-respirer. In addition, new efforts are being undertaken to isolate hydrogen-oxidizing As(V)-respirers, as well as aerobic As(III)-oxidizers from the extreme environment of Searles Lake.
DE: 4805 Biogeochemical cycles (1615)
DE: 4802 Anoxic environments
DE: 1065 Trace elements (3670)
DE: 1615 Biogeochemical processes (4805)
DE: 0400 Biogeosciences
SC: Hydrology [H]
MN: 2004 AGU Fall Meeting