N-157. Effects of Salinity and Temperature on Microbial Growth in Filtered Don Juan Pond Water-Antarctica

A. Chan, B. Lanoil, S. Han;
Univ. of California, Riverside, CA.

Don Juan Pond, Wright Valley, Antarctica, (DJP) may be the only known body of water on Earth without life. DJP is an extremely harsh environment, with mean annual temperatures around -20°C and extremely low water activity (0.2-0.6). To determine the effects of DJP water on living organisms, two culturing experiments with similar design but different inocula are underway. Seven dilutions of DJP water (0-100%) with 0.2% yeast extract as a carbon and energy source were inoculated and incubated in triplicate at 4°C and 15°C for up to six months. Inocula were from Lake Bonney, Taylor Valley, Antarctica (LB) or Lake Vanda, Wright Valley, Antarctica (LV). Both lakes are hypersaline; however, the dominant solute in LB is monovalent NaCl whereas LV is dominated by divalent CaCl2, as is DJP. With LB inoculum, growth was observed at a maximum of 25% DJP water at 15°C, and the highest cell density (1.64 X 109 cells ml-1) was observed in the 0% DJP at 15°C sample. In contrast, with LV inoculum, cell growth was observed at 50% DJP water at 15°C, and the highest cell density (6.62 X 108 cells ml-1) was observed in the 5% DJP water at 15°C. At different dilutions and temperatures, there are clear morphological differences. 16S rRNA gene-based community analyses are currently underway to characterize community composition in these samples. This project will examine effects of divalent hypersalinity and temperature on community composition. This research will increase understanding about DJP and extreme environments, the limits of life, and possibly life on other planets.