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Clade II nitrous oxide respiration of Wolinella succinogenes depends on the NosG, ‐C1, ‐C2, ‐H electron transport module, NosB and a Rieske/cytochrome bc complex
Author(s) -
Hein Sascha,
Witt Samantha,
Simon Jörg
Publication year - 2017
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 - 10.1111/1462-2920.13935
Subject(s) - electron transport chain , biology , cytochrome , biochemistry , mutant , nitrate reductase , anaerobic respiration , reductase , gene , bacteria , enzyme , genetics
Summary Microbial reduction of nitrous oxide (N 2 O) is an environmentally significant process in the biogeochemical nitrogen cycle. However, it has been recognized only recently that the gene encoding N 2 O reductase ( nosZ ) is organized in varying genetic contexts, thereby defining clade I (or ‘typical’) and clade II (or ‘atypical’) N 2 O reductases and nos gene clusters. This study addresses the enzymology of the clade II Nos system from Wolinella succinogenes , a nitrate‐ammonifying and N 2 O‐respiring Epsilonproteobacterium that contains a cytochrome c N 2 O reductase ( c NosZ). The characterization of single non‐polar nos gene deletion mutants demonstrated that the NosG, ‐C1, ‐C2, ‐H and ‐B proteins were essential for N 2 O respiration. Moreover, cells of a W. succinogenes mutant lacking a putative menaquinol‐oxidizing Rieske/cytochrome bc complex (QcrABC) were found to be incapable of N 2 O (and also nitrate) respiration. Proton motive menaquinol oxidation by N 2 O is suggested, supported by the finding that the molar yield for W. succinogenes cells grown by N 2 O respiration using formate as electron donor exceeded that of fumarate respiration by about 30%. The results demand revision of the electron transport chain model of clade II N 2 O respiration and challenge the assumption that NosGH(NapGH)‐type iron‐sulfur proteins are menaquinol‐reactive.