title: Distinct Anaerobic Bacterial Consumers of Cellobiose-Derived Carbon in Boreal Fens with Different CO2/CH4 Production Ratios.
abstract: Northern peatlands in general have high methane (CH4) emissions, but individual peatlands show considerable variation as CH4sources. Particularly in nutrient-poor peatlands, CH4production can be low and exceeded by carbon dioxide (CO2) production from unresolved anaerobic processes. To clarify the role anaerobic bacterial degraders play in this variation, we compared consumers of cellobiose-derived carbon in two fens differing in nutrient status and the ratio of CO2to CH4produced. After [13C]cellobiose amendment, the mesotrophic fen produced equal amounts of CH4and CO2The oligotrophic fen had lower CH4production but produced 3 to 59 times more CO2than CH4RNA stable-isotope probing revealed that in the mesotrophic fen with higher CH4production, cellobiose-derived carbon was mainly assimilated by various recognized fermenters of Firmicutes and by Proteobacteria The oligotrophic peat with excess CO2production revealed a wider variety of cellobiose-C consumers, including Firmicutes and Proteobacteria, but also more unconventional degraders, such as Telmatobacter-related Acidobacteria and subphylum 3 of Verrucomicrobia Prominent and potentially fermentative Planctomycetes and Chloroflexi did not appear to process cellobiose-C. Our results show that anaerobic degradation resulting in different levels of CH4production can involve distinct sets of bacterial degraders. By distinguishing cellobiose degraders from the total community, this study contributes to defining anaerobic bacteria that process cellulose-derived carbon in peat. Several of the identified degraders, particularly fermenters and potential Fe(III) or humic substance reducers in the oligotrophic peat, represent promising candidates for resolving the origin of excess CO2production in peatlands.
  
  
  
  Peatlands are major sources of the greenhouse gas methane (CH4), yet in many peatlands, CO2production from unresolved anaerobic processes exceeds CH4production. Anaerobic degradation produces the precursors of CH4production but also represents competing processes. We show that anaerobic degradation leading to high or low CH4production involved distinct sets of bacteria. Well-known fermenters dominated in a peatland with high CH4production, while novel and unconventional degraders could be identified in a site where CO2production greatly exceeds CH4production. Our results help identify and assign functions to uncharacterized bacteria that promote or inhibit CH4production and reveal bacteria potentially producing the excess CO2in acidic peat. This study contributes to understanding the microbiological basis for different levels of CH4emission from peatlands.
authors.affiliation: Department of Biosciences, General Microbiology, University of Helsinki, Helsinki, Finland heli.juottonen@alumni.helsinki.fi.|Department of Ecology and Genetics, Limnology, Uppsala University, Uppsala, Sweden.|Natural Resources Institute Finland, Helsinki, Finland.
authors.forename: Heli
authors.initials: H
authors.lastname: Juottonen
authors.affiliation: Department of Ecology and Genetics, Limnology, Uppsala University, Uppsala, Sweden.
authors.forename: Alexander
authors.initials: A
authors.lastname: Eiler
authors.affiliation: Department of Environmental and Biological Sciences, University of Eastern Finland, Kuopio, Finland.
authors.forename: Christina
authors.initials: C
authors.lastname: Biasi
authors.affiliation: School of Forest Sciences, University of Eastern Finland, Joensuu, Finland.
authors.forename: Eeva-Stiina
authors.initials: ES
authors.lastname: Tuittila
authors.affiliation: Department of Biosciences, General Microbiology, University of Helsinki, Helsinki, Finland.
authors.forename: Kim
authors.initials: K
authors.lastname: Yrjälä
authors.affiliation: Natural Resources Institute Finland, Helsinki, Finland.
authors.forename: Hannu
authors.initials: H
authors.lastname: Fritze
mesh_terms: D061271:Acidobacteria / Q000378:metabolism*; D000693:Anaerobiosis / Q000502:physiology; D001421:Bacteria, Anaerobic / Q000378:metabolism*; D002245:Carbon Dioxide / Q000378:metabolism*; D002475:Cellobiose / Q000378:metabolism*; D005285:Fermentation / Q000502:physiology; D000068536:Bacillota / Q000378:metabolism*; D008697:Methane / Q000378:metabolism*; D064307:Microbiota / Q000502:physiology; D020560:Proteobacteria / Q000378:metabolism*; D066188:Taiga; D053833:Wetlands
chemical_list: D002245:Carbon Dioxide; D002475:Cellobiose; D008697:Methane
keywords: anaerobic degradation; greenhouse gas; methane; microbial communities; peat; stable-isotope probing; wetland