N-153. Microbial Phospholipid Fatty Acid (PLFA) Profiles of Core Samples from Two Geochemically Distinct Thermal Pools in Kamchatka, Far East Russia

E. A. Burgess1, J. M. Unrine1,2, J. Wiegel3, G. L. Mills1;
1Univ. of Georgia, Aiken, SC, 2Univ. of Kentucky, Lexington, KY, 3Univ. of Georgia, Athens, GA.

Characterization of two geochemically distinct thermal pools, Arkashin Schurf (Arkashin) and Zavarzin II Spring (Zavarzin), in the Uzon Caldera has been ongoing as part of a NSF-Microbial Observatory in Kamchatka, Far East Russia. In 2006, additional core samples were collected at each pool and changes in solid-phase sediment chemistry and microbial community structure with depth were determined using inductively coupled plasma mass spectrometry and PLFA profiling. Of particular interest was the concentration of arsenic, ranging approximately from 8 to 110 ppm in Zavarzin and 1317 to 75568 ppm in Arkashin. Changes in sediment chemistry with depth were consistent with those observed in core samples from 2005, including an arsenic concentration maximum (75568 ppm) at approximately 13 cm from the surface in Arkashin. Total lipids were extracted from freeze dried sediment, yielding a range of 1 to 65 μg lipid/g of sample. Total lipid yield was generally higher in Zavarzin, although the highest individual yield was from the Arkashin surface sample. Yield from both pools decreased with increasing depth. The most common PLFA, present in all samples, were 16:0 (5.9-34.0%) and 16:1ω7c (0.7-13.1%), though the dominance of lipids varied among samples. In samples from Zavarzin, the occurrence of 16:1ω7c (2.8-13.1%) along with 18:1ω7c (10.2-27%) and 16:0 (9.7-17%), suggested the presence of sulfur-oxidizing organisms. Biomarkers indicative of sulfate-reducing microorganisms (e.g. 10Me16:0 and i17:1) were minor components or absent in profiles from both pools. This was consistent with previous observations of little or no sulfate reduction in 2005 core samples from these pools. The addition of lipid biomarker data to the suite of characteristics analyzed in these pools has enhanced our interpretation of their geochemical and microbiological dynamics.