title: Syntrophic associations from hypersaline soda lakes converting organic acids and alcohols to methane at extremely haloalkaline conditions.
abstract: Until now anaerobic oxidation of VFA at high salt-pH has been demonstrated only at sulfate-reducing conditions. Here, we present results of a microbiological investigation of anaerobic conversion of organic acids and alcohols at methanogenic conditions by syntrophic associations enriched from hypersaline soda lakes in Central Asia. Sediment incubation experiments showed active, albeit very slow, methane formation from acetate, propionate, butyrate and C2 C4 alcohols at pH 10 and various levels of salinity. Enrichments of syntrophic associations using hydrogenotrophic members of the genus Methanocalculus from soda lakes as partners resulted in several highly enriched cultures converting acetate, propionate, butyrate, benzoate and EtOH to methane. Most syntrophs belonged to Firmicutes, while the propionate-oxidizer formed a novel lineage within the family Syntrophobacteraceae in the Deltaproteobacteria. The acetate-oxidizing syntroph was identified as 'Ca. Syntrophonatronum acetioxidans' previously found to oxidize acetate at sulfate-reducing conditions up to salt-saturating concentrations. Butyrate and a benzoate-degrading syntrophs represent novel genus-level lineages in Syntrophomonadales which are proposed as Candidatus taxons 'Syntrophobaca', 'Syntrophocurvum' and 'Syntropholuna'. Overall, despite very slow growth, the results indicated the presence of a functionally competent syntrophic community in hypersaline soda lakes, capable of efficient oxidation of fermentation products to methane at extremely haloalkaline conditions.
authors.affiliation: Winogradsky Institute of Microbiology, Research Centre of Biotechnology, Russian Academy of Sciences, Moscow, Russia. soroc@inmi.ru.|Department of Biotechnology, Delft University of Technology, 2628, Delft, BC, The Netherlands. soroc@inmi.ru.
authors.forename: Dimitry Y
authors.initials: DY
authors.lastname: Sorokin
authors.affiliation: Department of Biotechnology, Delft University of Technology, 2628, Delft, BC, The Netherlands.
authors.forename: Ben
authors.initials: B
authors.lastname: Abbas
authors.affiliation: Department of Biotechnology, Delft University of Technology, 2628, Delft, BC, The Netherlands.
authors.forename: Mitchell
authors.initials: M
authors.lastname: Geleijnse
authors.affiliation: Centre Bioengineering, Research Centre of Biotechnology, Russian Academy of Sciences, Moscow, Russia.
authors.forename: Tatjana V
authors.initials: TV
authors.lastname: Kolganova
authors.affiliation: Department of Biotechnology, Delft University of Technology, 2628, Delft, BC, The Netherlands.
authors.forename: Robbert
authors.initials: R
authors.lastname: Kleerebezem
authors.affiliation: Department of Biotechnology, Delft University of Technology, 2628, Delft, BC, The Netherlands.
authors.forename: Mark C M
authors.initials: MC
authors.lastname: van Loosdrecht
mesh_terms: D000085:Acetates / Q000378:metabolism; D000143:Acids / Q000378:metabolism*; D000438:Alcohols / Q000378:metabolism*; D002087:Butyrates / Q000378:metabolism; D020564:Deltaproteobacteria / Q000145:classification / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D060106:Lakes / Q000737:chemistry / Q000382:microbiology*; D008697:Methane / Q000378:metabolism*; D010084:Oxidation-Reduction; D011422:Propionates / Q000378:metabolism; D054712:Salinity; D012965:Sodium Chloride / Q000032:analysis* / Q000378:metabolism
chemical_list: D000085:Acetates; D000143:Acids; D000438:Alcohols; D002087:Butyrates; D011422:Propionates; D012965:Sodium Chloride; D008697:Methane