title: Integration of Metagenomic and Stable Carbon Isotope Evidence Reveals the Extent and Mechanisms of Carbon Dioxide Fixation in High-Temperature Microbial Communities.
abstract: Although the biological fixation of CO2by chemolithoautotrophs provides a diverse suite of organic compounds utilized by chemoorganoheterotrophs as a carbon and energy source, the relative amounts of autotrophic C in chemotrophic microbial communities are not well-established. The extent and mechanisms of CO2fixation were evaluated across a comprehensive set of high-temperature, chemotrophic microbial communities in Yellowstone National Park by combining metagenomic and stable13C isotope analyses. Fifteen geothermal sites representing three distinct habitat types (iron-oxide mats, anoxic sulfur sediments, and filamentous "streamer" communities) were investigated. Genes of the 3-hydroxypropionate/4-hydroxybutyrate, dicarboxylate/4-hydroxybutyrate, and reverse tricarboxylic acid CO2fixation pathways were identified in assembled genome sequence corresponding to the predominant Crenarchaeota and Aquificales observed across this habitat range. Stable13C analyses of dissolved inorganic and organic C (DIC, DOC), and possible landscape C sources were used to interpret the13C content of microbial community samples. Isotope mixing models showed that the minimum fractions of autotrophic C in microbial biomass were >50% in the majority of communities analyzed. The significance of CO2as a C source in these communities provides a foundation for understanding community assembly and succession, and metabolic linkages among early-branching thermophilic autotrophs and heterotrophs.
authors.affiliation: Department of Land Resources and Environmental Sciences, Montana State UniversityBozeman, MT, USA; Thermal Biology Institute, Montana State UniversityBozeman, MT, USA.
authors.forename: Ryan de Montmollin
authors.initials: RM
authors.lastname: Jennings
authors.affiliation: Pacific Northwest National Laboratories Richland, WA, USA.
authors.forename: James J
authors.initials: JJ
authors.lastname: Moran
authors.affiliation: Department of Land Resources and Environmental Sciences, Montana State UniversityBozeman, MT, USA; Thermal Biology Institute, Montana State UniversityBozeman, MT, USA.
authors.forename: Zackary J
authors.initials: ZJ
authors.lastname: Jay
authors.affiliation: Department of Land Resources and Environmental Sciences, Montana State UniversityBozeman, MT, USA; Thermal Biology Institute, Montana State UniversityBozeman, MT, USA.
authors.forename: Jacob P
authors.initials: JP
authors.lastname: Beam
authors.affiliation: Pacific Northwest National Laboratories Richland, WA, USA.
authors.forename: Laura M
authors.initials: LM
authors.lastname: Whitmore
authors.affiliation: Department of Land Resources and Environmental Sciences, Montana State University Bozeman, MT, USA.
authors.forename: Mark A
authors.initials: MA
authors.lastname: Kozubal
authors.affiliation: Pacific Northwest National Laboratories Richland, WA, USA.
authors.forename: Helen W
authors.initials: HW
authors.lastname: Kreuzer
authors.affiliation: Department of Land Resources and Environmental Sciences, Montana State UniversityBozeman, MT, USA; Thermal Biology Institute, Montana State UniversityBozeman, MT, USA.
authors.forename: William P
authors.initials: WP
authors.lastname: Inskeep
keywords: Aquificales; CO2 fixation; Crenarchaeota; autotrophy; geothermal; stable C isotopes