{"id":14481,"date":"2020-02-03T14:32:19","date_gmt":"2020-02-03T22:32:19","guid":{"rendered":"https:\/\/www.darkenergybiosphere.org\/?post_type=publication&#038;p=14481"},"modified":"2020-02-18T12:31:52","modified_gmt":"2020-02-18T20:31:52","slug":"lower-hydrogen-flux-leads-to-larger-carbon-isotopic-fractionation-of-methane-and-biomarkers-during-hydrogenotrophic-methanogenesis","status":"publish","type":"publication","link":"https:\/\/www.darkenergybiosphere.org\/publication\/lower-hydrogen-flux-leads-to-larger-carbon-isotopic-fractionation-of-methane-and-biomarkers-during-hydrogenotrophic-methanogenesis\/","title":{"rendered":"Lower hydrogen flux leads to larger carbon isotopic fractionation of methane and biomarkers during hydrogenotrophic methanogenesis"},"content":{"rendered":"<p id=\"sp0005\">The isotopic composition of lipid biomarkers and biomass in sedimentary environments are widely used to infer microbial metabolisms and constrain carbon cycling processes. It has been observed that metabolic energy availability in the form of H<sub>2<\/sub>\u00a0impacts the stable carbon isotopes of CH<sub>4<\/sub>\u00a0during hydrogenotrophic methanogenesis, but it is unknown whether this relationship extends to lipids and amino acids. Since lipids and amino acids are long-lived, they can be used to reconstruct past conditions over geologic timescales. Therefore, the controls on their isotopic signatures are important to constrain to better interpret past environments.<\/p>\n<p id=\"sp0010\">In this study, the isotopic distributions of carbon metabolized and reduced by the hyperthermophile\u00a0<em>Methanocaldococcus jannaschii<\/em>\u00a0were quantified following growth at 82\u202f\u00b0C in a chemostat with high (80\u201383\u202f\u00b5M) and low (15\u201327\u202f\u00b5M) H<sub>2<\/sub>\u00a0concentrations. As has been shown previously, the stable carbon isotope fractionation factors for CH<sub>4<\/sub>\u00a0were &gt;15\u2030 larger in low H<sub>2<\/sub>\u00a0experiments than in high H<sub>2<\/sub>\u00a0experiments. Lipid biomarkers and amino acids were similarly impacted with approximately 10\u2030 larger fractionation factors under low H<sub>2<\/sub>\u00a0conditions. The increase in fractionation factors can be related to the lower availability of thermodynamic energy, suggesting that even larger fractionation factors would be observed in methanogens living close to their threshold energy needs, as they do in most environments. The resulting isotopic signatures of long-lived lipid biomarkers synthesized by hydrogenotrophic methanogens may become as \u2018superlight\u2019 as those synthesized by archaea carrying out the anaerobic oxidation of methane. These results help to describe the underlying mechanisms that determine the isotopic composition of long-lived biomarkers and provide constraints for interpreting these signatures in the environment.<\/p>\n","protected":false},"template":"","tags":[],"publication_type":[19],"_links":{"self":[{"href":"https:\/\/www.darkenergybiosphere.org\/wp-json\/wp\/v2\/publication\/14481"}],"collection":[{"href":"https:\/\/www.darkenergybiosphere.org\/wp-json\/wp\/v2\/publication"}],"about":[{"href":"https:\/\/www.darkenergybiosphere.org\/wp-json\/wp\/v2\/types\/publication"}],"wp:attachment":[{"href":"https:\/\/www.darkenergybiosphere.org\/wp-json\/wp\/v2\/media?parent=14481"}],"wp:term":[{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.darkenergybiosphere.org\/wp-json\/wp\/v2\/tags?post=14481"},{"taxonomy":"publication_type","embeddable":true,"href":"https:\/\/www.darkenergybiosphere.org\/wp-json\/wp\/v2\/publication_type?post=14481"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}