%0 Journal Article %A William D. Leavitt %A Theodore M. Flynn %A Melanie K. Suess %A Alexander S. Bradley %T Effects of transhydrogenase and growth substrates on lipid D/H ratios in Desulfovibrio alaskensis G20 %D 2016 %R 10.1101/039792 %J bioRxiv %P 039792 %X Microbial fatty acids preserve metabolic and environmental information in their ratios of deuterium (D) to hydrogen (H). This ratio is influenced by parameters that include the D/H of water in the microbial growth environment, and biosynthetic fractionations between water and lipid. In some microbes, this biosynthetic fractionation has been shown to vary systematically with central energy metabolism, and controls on fatty acid D/H may be linked to the intracellular production of NADPH. We examined the apparent fractionation between media water and the fatty acids produced by Desulfovibrio alaskensis G20. Growth was in batch culture with malate as an electron donor for sulfate respiration, and with pyruvate and fumarate as substrates for fermentation or sulfate respiration. A larger fractionation was observed as a consequence of respiratory or fermentative growth on pyruvate than growth on fumarate or malate. This difference correlates with opposite flows of electrons through the electron bifurcating/confurcating transhydrogenase NfnAB. When grown on malate or fumarate, mutant strains of D. alaskensis G20 containing transposon disruptions in a nfnAB paralog show different fractionations than the wild type strain. This isotopic phenotype is muted during fermentative growth on pyruvate, and it is absent when pyruvate is a substrate for sulfate reduction. All strains and conditions produced similar fatty acid profiles, and the D/H of individual lipids changed in concert with the mass-weighted average. We found that fractionation correlated strongly with growth rate, a pattern that has also been observed in the fractionation of sulfur isotopes during dissimilatory sulfate reduction by sulfate reducing bacteria. %U https://www.biorxiv.org/content/biorxiv/early/2016/02/17/039792.full.pdf