title: Consortia of low-abundance bacteria drive sulfate reduction-dependent degradation of fermentation products in peat soil microcosms.
abstract: Dissimilatory sulfate reduction in peatlands is sustained by a cryptic sulfur cycle and effectively competes with methanogenic degradation pathways. In a series of peat soil microcosms incubated over 50 days, we identified bacterial consortia that responded to small, periodic additions of individual fermentation products (formate, acetate, propionate, lactate or butyrate) in the presence or absence of sulfate. Under sulfate supplementation, net sulfate turnover (ST) steadily increased to 16-174 nmol cm(-3) per day and almost completely blocked methanogenesis. 16S rRNA gene and cDNA amplicon sequencing identified microorganisms whose increases in ribosome numbers strongly correlated to ST. Natively abundant (⩾0.1% estimated genome abundance) species-level operational taxonomic units (OTUs) showed no significant response to sulfate. In contrast, low-abundance OTUs responded significantly to sulfate in incubations with propionate, lactate and butyrate. These OTUs included members of recognized sulfate-reducing taxa (Desulfosporosinus, Desulfopila, Desulfomonile, Desulfovibrio) and also members of taxa that are either yet unknown sulfate reducers or metabolic interaction partners thereof. Most responsive OTUs markedly increased their ribosome content but only weakly increased in abundance. Responsive Desulfosporosinus OTUs even maintained a constantly low population size throughout 50 days, which suggests a novel strategy of rare biosphere members to display activity. Interestingly, two OTUs of the non-sulfate-reducing genus Telmatospirillum (Alphaproteobacteria) showed strongly contrasting preferences towards sulfate in butyrate-amended microcosms, corroborating that closely related microorganisms are not necessarily ecologically coherent. We show that diverse consortia of low-abundance microorganisms can perform peat soil sulfate reduction, a process that exerts control on methane production in these climate-relevant ecosystems.
authors.affiliation: Division of Microbial Ecology, Department of Microbiology and Ecosystem Science, Research Network Chemistry Meets Microbiology, University of Vienna, Vienna, Austria.|Department of Biology, University of Konstanz, Konstanz, Germany.
authors.forename: Bela
authors.identifier: 0000-0002-0846-1202
authors.initials: B
authors.lastname: Hausmann
authors.affiliation: Hydrology Group, Institute of Landscape Ecology, University of Münster, Münster, Germany.
authors.forename: Klaus-Holger
authors.identifier: 0000-0003-4175-0214
authors.initials: KH
authors.lastname: Knorr
authors.affiliation: Division of Microbial Ecology, Department of Microbiology and Ecosystem Science, Research Network Chemistry Meets Microbiology, University of Vienna, Vienna, Austria.
authors.forename: Katharina
authors.initials: K
authors.lastname: Schreck
authors.affiliation: Joint Genome Institute, US Department of Energy, Walnut Creek, CA, USA.
authors.forename: Susannah G
authors.identifier: 0000-0001-6479-8427
authors.initials: SG
authors.lastname: Tringe
authors.affiliation: Joint Genome Institute, US Department of Energy, Walnut Creek, CA, USA.
authors.forename: Tijana
authors.initials: T
authors.lastname: Glavina Del Rio
authors.affiliation: Division of Microbial Ecology, Department of Microbiology and Ecosystem Science, Research Network Chemistry Meets Microbiology, University of Vienna, Vienna, Austria.
authors.forename: Alexander
authors.identifier: 0000-0001-8923-5882
authors.initials: A
authors.lastname: Loy
authors.affiliation: Division of Microbial Ecology, Department of Microbiology and Ecosystem Science, Research Network Chemistry Meets Microbiology, University of Vienna, Vienna, Austria.|Department of Biology, University of Konstanz, Konstanz, Germany.
authors.forename: Michael
authors.identifier: 0000-0001-6296-4145
authors.initials: M
authors.lastname: Pester
mesh_terms: D001419:Bacteria / Q000145:classification / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D017753:Ecosystem; D005285:Fermentation; D008697:Methane / Q000378:metabolism; D059013:Microbial Consortia; D010084:Oxidation-Reduction; D012988:Soil Microbiology; D013431:Sulfates / Q000378:metabolism*; D013455:Sulfur / Q000378:metabolism
chemical_list: D013431:Sulfates; D013455:Sulfur; D008697:Methane