High-rate, High Temperature Acetotrophic Methanogenesis Governed by a Three Population Consortium in Anaerobic Bioreactors

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Ho, Dang ; Jensen, Paul ; Gutierrez-Zamora, Maria-Luisa ; Beckmann, Sabrina ; Manefield, Mike ; Batstone, Damien (2016)
  • Publisher: Public Library of Science
  • Journal: PLoS ONE, volume 11, issue 8 (issn: 1932-6203, eissn: 1932-6203)
  • Related identifiers: doi: 10.1371/journal.pone.0159760, pmc: PMC4973872
  • Subject: RNA extraction | Molecular Biology | Research Article | Archaean Biology | Materials by Structure | Chemical Compounds | Ribosomes | Physical Sciences | Molecular Biology Techniques | Archaeans | Sequence Analysis | Database and Informatics Methods | Chemistry | Sequence Databases | Sequencing Techniques | Biology and Life Sciences | Non-coding RNA | Sludge | RNA | Biological Databases | Materials Science | Extraction techniques | Research and Analysis Methods | Microbiology | Medicine | Nucleic acids | Methanogens | Q | RNA sequencing | R | Cell biology | Cellular structures and organelles | Science | Biochemistry | Ribosomal RNA | Methane | Organisms

A combination of acetate oxidation and acetoclastic methanogenesis has been previously identified to enable high-rate methanogenesis at high temperatures (55 to 65°C), but this capability had not been linked to any key organisms. This study combined RNA-stable isotope probing on 13C-labelled acetate and 16S amplicon sequencing to identify the active micro-organisms involved in high-rate methanogenesis. Active biomass was harvested from three bench-scale thermophilic bioreactors treating waste activated sludge at 55, 60 and 65°C, and fed with 13-C labelled and 12C-unlabelled acetate. Acetate uptake and cumulative methane production were determined and kinetic parameters were estimated using model-based analysis. Pyrosequencing performed on 13C- enriched samples indicated that organisms accumulating labelled carbon were Coprothermobacter (all temperatures between 55 and 65°C), acetoclastic Methanosarcina (55 to 60°C) and hydrogenotrophic Methanothermobacter (60 to 65°C). The increased relative abundance of Coprothermobacter with increased temperature corresponding with a shift to syntrophic acetate oxidation identified this as a potentially key oxidiser. Methanosarcina likely acts as both a hydrogen utilising and acetoclastic methanogen at 55°C, and is replaced by Methanothermobacter as a hydrogen utiliser at higher temperatures.
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