{"id":14345,"date":"2020-01-06T12:36:06","date_gmt":"2020-01-06T20:36:06","guid":{"rendered":"https:\/\/www.darkenergybiosphere.org\/?post_type=publication&#038;p=14345"},"modified":"2020-01-06T12:36:07","modified_gmt":"2020-01-06T20:36:07","slug":"methane-linked-mechanisms-of-electron-uptake-from-cathodes-by-methanosarcina-barkeri","status":"publish","type":"publication","link":"https:\/\/www.darkenergybiosphere.org\/publication\/methane-linked-mechanisms-of-electron-uptake-from-cathodes-by-methanosarcina-barkeri\/","title":{"rendered":"Methane-Linked Mechanisms of Electron Uptake from Cathodes by Methanosarcina barkeri"},"content":{"rendered":"<p>The\u00a0<em>Methanosarcinales<\/em>, a lineage of cytochrome-containing methanogens, have recently been proposed to participate in direct extracellular electron transfer interactions within syntrophic communities. To shed light on this phenomenon, we applied electrochemical techniques to measure electron uptake from cathodes by\u00a0<span id=\"named-content-3\" class=\"named-content genus-species\">Methanosarcina barkeri<\/span>, which is an important model organism that is genetically tractable and utilizes a wide range of substrates for methanogenesis. Here, we confirm the ability of\u00a0<span id=\"named-content-4\" class=\"named-content genus-species\">M. barkeri<\/span>\u00a0to perform electron uptake from cathodes and show that this cathodic current is linked to quantitative increases in methane production. The underlying mechanisms we identified include, but are not limited to, a recently proposed association between cathodes and methanogen-derived extracellular enzymes (e.g., hydrogenases) that can facilitate current generation through the formation of reduced and diffusible methanogenic substrates (e.g., hydrogen). However, after minimizing the contributions of such extracellular enzymes and using a mutant lacking hydrogenases, we observe a lower-potential hydrogen-independent pathway that facilitates cathodic activity coupled to methane production in\u00a0<span id=\"named-content-5\" class=\"named-content genus-species\">M. barkeri<\/span>. Our electrochemical measurements of wild-type and mutant strains point to a novel and hydrogenase-free mode of electron uptake with a potential near \u2212484\u2009mV versus standard hydrogen electrode (SHE) (over 100\u2009mV more reduced than the observed hydrogenase midpoint potential under these conditions). These results suggest that\u00a0<span id=\"named-content-6\" class=\"named-content genus-species\">M. barkeri<\/span>\u00a0can perform multiple modes (hydrogenase-mediated and free extracellular enzyme-independent modes) of electrode interactions on cathodes, including a mechanism pointing to a direct interaction, which has significant applied and ecological implications.<\/p>\n","protected":false},"template":"","tags":[],"publication_type":[19],"_links":{"self":[{"href":"https:\/\/www.darkenergybiosphere.org\/wp-json\/wp\/v2\/publication\/14345"}],"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=14345"}],"wp:term":[{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.darkenergybiosphere.org\/wp-json\/wp\/v2\/tags?post=14345"},{"taxonomy":"publication_type","embeddable":true,"href":"https:\/\/www.darkenergybiosphere.org\/wp-json\/wp\/v2\/publication_type?post=14345"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}