MICROBIAL LIPID BIOGEOCHEMISTRY OF HOT SPRINGS IN KAMCHATKA, RUSSIA

Numerous hot springs exist in the Kamchatka Peninsula in Russia, which are associated with more than 30 active volcanoes. This study focused on five prominent hot springs, which have water temperatures ranging from 40-90 ºC and pH ranging from 5.6-5.9. Our goal was to determine the microbial carbon-flow pathways in different chemical environments using lipid biomarkers of Bacteria and Archaea. Microbial mats or sediments were freeze-dried and extracted for total lipids. The lipids were fractionated into hydrocarbons, sterols, ether lipids, free fatty acids, and phospholipid fatty acids (PLFA). Among these fractions, PLFA would indicate the community structure and abundance of the Bacteria and ether lipids the Archaea. Results of PLFA showed 16:0 as the most abundant compound (33-44%), which is universal in all living organisms. Other significant biomarkers included 18:1 (19-24%), 18:2 (5-13%),16:1 (3-12%), and 18:0 (2-7%). These biomarkers are characteristic of cyanobacteria, green-sulfur bacteria, and green non-sulfur bacteria, which are common autotrophic organisms in terrestrial hot springs (Zhang et al., 2004). On the other hand, biomarkers of heterotrophic bacteria, such as iso- and anteiso-15:0 were low (2-8%). These results indicate that bacterial carbon cycle is dominated by autotrophic organisms in the Kamchatka hot springs. Ether lipids in these samples were also present in significant abundance. Experiments are ongoing to determine the isotopic compositions of both bacterial and archaeal lipids to link carbon metabolism of the extant microorganisms with inorganic and organic carbon sources fueling them.