Bacterial physiology highlighted by the δ13C fractionation of bacteriohopanetetrol isomers

Lipid biomarkers, such as the various bacteriohopanetetrol (BHT) isomers studied here, are useful tools in tracing bacterially mediated nitrogen and carbon cycle processes affecting greenhouse gas emissions, including anaerobic oxidation of ammonia. Three BHT occur commonly environment. By chromatography, BHT-34S elutes first; it is produced by numerous bacteria. The two later eluting more constrained their origin. marine anammox bacteria ‘Ca. Scalindua’ only known producer a isomer unknown stereochemistry (BHT-x), making BHT-x diagnostic biomarker anoxic settings. BHT-34R three freshwater aerobic heterotrophic producers (Frankia spp., Acetobacter pasteurianus, Komagataeibacter xylinus), serine-cycle (Type II) methanotroph (Methylocella palustris), Brocadia’, which makes detection using complicated. We investigated whether source environments could be ascertained via its δ13C value. used conventional on-column chromatography-combustion-isotope ratio mass spectrometry (GC-C-IRMS) (as opposed to high temperature GC-C-IRMS) determine composition acetylated cultured bacterial enrichments. combined these with bulk biomass substrate compositions establish isotopic fractionation factors. genera had large factors from dissolved inorganic (DIC) (Δ13Cbiomass – DIC = –43.8 –26.4 ‰) BHTs (Δ13CBHT –53.8 –38.2 ‰), clearly distinguished them –2.3 –0.1 ‰; Δ13CBHT –12.8 5.2 ‰). Methylocella assimilated mainly DIC, rather than methane, into BHT, previous work suggested this assimilation comes relatively small fractionation. Thus, peatlands, values would not reflect low biogenic methane. Consequently, presence relates Brocadia’ presents novel tool trace environments.