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Formate‐derived H 2 , a driver of hydrogenotrophic processes in the root‐zone of a methane‐emitting fen
Author(s) -
Hunger Sindy,
Schmidt Oliver,
Gößner Anita S.,
Drake Harold L.
Publication year - 2016
Publication title -
environmental microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.954
H-Index - 188
eISSN - 1462-2920
pISSN - 1462-2912
DOI - 10.1111/1462-2920.13301
Subject(s) - formate , methanogenesis , formate dehydrogenase , biology , acetogenesis , methane , hydrogenase , botany , biochemistry , ecology , enzyme , catalysis
Summary Wetlands are important sources of globally emitted methane. Plants mediate much of that emission by releasing root‐derived organic carbon, including formate, a direct precursor of methane. Thus, the objective of this study was to resolve formate‐driven processes potentially linked to methanogenesis in the fen root‐zone. Although, formate was anticipated to directly trigger methanogenesis, the rapid anaerobic consumption of formate by Carex roots unexpectedly yielded H 2 and CO 2 via enzymes such as formate‐H 2 ‐lyase (FHL), and likewise appeared to enhance the utilization of organic carbon. Collectively, 57 [FeFe]‐ and [NiFe]‐hydrogenase‐containing family level phylotypes potentially linked to FHL activity were detected. Under anoxic conditions, root‐derived fermentative Citrobacter and Hafnia isolates produced H 2 from formate via FHL. Formate‐derived H 2 fueled methanogenesis and acetogenesis, and methanogenic ( Methanoregula , Methanobacterium , Methanocella ) and acetogenic ( Acetonema , Clostridum , Sporomusa ) genera potentially linked to these hydrogenotrophic activities were identified. The findings (i) provide novel insights on highly diverse root‐associated FHL‐containing taxa that can augment secondary hydrogenotrophic processes via the production of formate‐derived H 2 , (ii) demonstrate that formate can have a ‘priming’ effect on the utilization of organic carbon, and (iii) raise questions regarding the fate of formate‐derived H 2 when it diffuses away from the root‐zone.