Extreme Life: A Representative Sulfate Reducing Bacterium from a Micro-oxic, Deep Subsurface Well in Death Valley, California
Mentor:Lily Momper, Ph.D. student, Marine Ecology and Biology, University of Southern California
The Nevares Deep well is a freshwater artesian well in Death Valley, California. Within the next two years it will be tapped as a drinking water source. The well is known to be very low energy with low dissolved organic carbon, 0.12mg/L, and low dissolved oxygen, 0.4mg/L, which makes it an extreme environment. If subsurface microbial communities, specifically the sulfate reducing prokaryotic community survive in this extreme environment, the well may potentially harbor organisms with novel metabolisms of interest for extrapolation to other low energy ecosystems where they have poorly constrained requirements for life such as water, carbon, nutrients, water and light or chemical energy, for example those found on other planetary bodies. Cultures were inoculated with anoxically-sampled Nevares bulk water and incubated in the dark at 30 o C. Culture growth was seen by increased turbidity in the culture vessel and increased absorbance at 600nm as measured on the spectrophotometer. Genomic DNA was extracted from this enrichment using fresh lysis buffer and phenol chloroform extraction followed by ethanol precipitation. The 16s gene of the extracted DNA was amplified via polymerase chain reaction (PCR) with universal bacterial 16s primers 8f and 1492 reverse. Amplification was checked on an agarose gel (1.2%) with UV illumination. The nucleotide base pair sequence of the 16s gene amplified from the Nevares well bacterial sulfate-reducer enrichment was most closely related to Desulfovibrio vulgaris sp. (98% coverage and 99% identity), a facultative autotrophic sulfate reducer. A liquid serial dilution was made in autotrophic sulfate reducer specific medium to dilute contaminating cells to extinction. However, due to slow cell doubling time the results of that dilution have not yet been analyzed. These chemolithoautotrophic bacteria, which require low energy, give insight for extrapolation to ancient metabolisms that may emerge or survive on extraterrestrial planets.