title: Identification of syntrophic acetate-oxidizing bacteria in anaerobic digesters by combined protein-based stable isotope probing and metagenomics.
abstract: Inhibition of anaerobic digestion through accumulation of volatile fatty acids occasionally occurs as the result of unbalanced growth between acidogenic bacteria and methanogens. A fast recovery is a prerequisite for establishing an economical production of biogas. However, very little is known about the microorganisms facilitating this recovery. In this study, we investigated the organisms involved by a novel approach of mapping protein-stable isotope probing (protein-SIP) onto a binned metagenome. Under simulation of acetate accumulation conditions, formations of (13)C-labeled CO2 and CH4 were detected immediately following incubation with [U-(13)C]acetate, indicating high turnover rate of acetate. The identified (13)C-labeled peptides were mapped onto a binned metagenome for improved identification of the organisms involved. The results revealed that Methanosarcina and Methanoculleus were actively involved in acetate turnover, as were five subspecies of Clostridia. The acetate-consuming organisms affiliating with Clostridia all contained the FTFHS gene for formyltetrahydrofolate synthetase, a key enzyme for reductive acetogenesis, indicating that these organisms are possible syntrophic acetate-oxidizing (SAO) bacteria that can facilitate acetate consumption via SAO, coupled with hydrogenotrophic methanogenesis (SAO-HM). This study represents the first study applying protein-SIP for analysis of complex biogas samples, a promising method for identifying key microorganisms utilizing specific pathways.
authors.affiliation: Department of Chemistry and Bioscience, Aalborg University, Aalborg, Denmark.
authors.forename: Freya
authors.initials: F
authors.lastname: Mosbæk
authors.affiliation: Department of Chemistry and Bioscience, Aalborg University, Aalborg, Denmark.
authors.forename: Henrik
authors.initials: H
authors.lastname: Kjeldal
authors.affiliation: Department of Engineering, Aarhus University, Aarhus, Denmark.
authors.forename: Daniel G
authors.initials: DG
authors.lastname: Mulat
authors.affiliation: Department of Chemistry and Bioscience, Aalborg University, Aalborg, Denmark.
authors.forename: Mads
authors.initials: M
authors.lastname: Albertsen
authors.affiliation: Department of Engineering, Aarhus University, Aarhus, Denmark.
authors.forename: Alastair J
authors.initials: AJ
authors.lastname: Ward
authors.affiliation: Department of Engineering, Aarhus University, Aarhus, Denmark.
authors.forename: Anders
authors.initials: A
authors.lastname: Feilberg
authors.affiliation: Department of Chemistry and Bioscience, Aalborg University, Aalborg, Denmark.
authors.forename: Jeppe L
authors.initials: JL
authors.lastname: Nielsen
mesh_terms: D000085:Acetates / Q000378:metabolism*; D000693:Anaerobiosis; D001419:Bacteria / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification* / Q000378:metabolism*; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D056804:Biofuels / Q000032:analysis; D002247:Carbon Isotopes / Q000378:metabolism; D005232:Fatty Acids, Volatile / Q000378:metabolism; D007553:Isotope Labeling; D056186:Metagenomics; D008697:Methane / Q000378:metabolism; D010084:Oxidation-Reduction
chemical_list: D000085:Acetates; D001426:Bacterial Proteins; D056804:Biofuels; D002247:Carbon Isotopes; D005232:Fatty Acids, Volatile; D008697:Methane