TRACKING CARBON METABOLISM IN NOVEL ANAEROBIC ALKANE-OXIDIZING ENRICHMENT CULTURES WITH ISOTOPE PATTERN MATCHING

Summary Recent studies suggest an unforeseen role of archaea in the anaerobic oxidation of non-methane alkanes using enzymes of the methanogenesis pathway and requiring partnerships with bacteria that have not yet been cultured. Stable isotope probing (SIP) approaches provide an important culture-independent tool to track activity and carbon assimilation of these microorganisms in situ. However, the established stable isotope probing of lipids requires labor-intense purification of individual molecules and chemical derivatization or cleavage reactions such as ether-cleavage or saponification to produce GC-irmMS-amenable derivatives. A recently developed promising technique is isotope pattern matching (IPM) which uses isotopomer patterns of intact lipids analyzed by HPLC-MS to determine uptake of stable isotopes. We have incubated methane- and other short chain alkane-oxidizing enrichment cultures from hydrothermal sites in the Guaymas Basin with 13C-labeled bicarbonate and 13C-labeled alkane substrates at 50°C and monitored label-uptake into the lipid pool using traditional SIP and IPM methods. This presentation will show data of diagnostic lipids, including intact polar archaeal and bacterial lipids and compare IPM with traditional SIP experiments of selected biomarkers with the goal to understand carbon substrate affinity of alkane-oxidizing enrichment cultures.