Although metabolic pathways and associated enzymes of anaerobic ammonium oxidation (anammox) of “Ca. Kuenenia stuttgartiensis” have been studied, those of other anammox bacteria are still poorly understood. NO2- reduction to NO is considered to be the first step in the anammox metabolism of “Ca. K. stuttgartiensis”, however, “Ca. Brocadia” lacks the genes that encode canonical NO-forming nitrite reductases (NirS or NirK) in its genome, which is different from “Ca. K. stuttgartiensis”. Here, we studied the anammox metabolism of “Ca. Brocadia sinica”. 15N-tracer experiments demonstrated that “Ca. B. sinica” cells could reduce NO2- to NH2OH, instead of NO, with as yet unidentified nitrite reductase(s). Furthermore, N2H4 synthesis, downstream reaction of NO2- reduction, was investigated using a purified “Ca. B. sinica” hydrazine synthase (Hzs) and intact cells. Both the “Ca. B. sinica” Hzs and cells utilized NH2OH and NH4+, but not NO and NH4+, for N2H4 synthesis and further oxidized N2H4 to N2 gas. Taken together, the metabolic pathway of “Ca. B. sinica” is NH2OH-dependent and different from the one of “Ca. K. stuttgartiensis”, indicating metabolic diversity of anammox bacteria. This article is protected by copyright. All rights reserved.
Bibliographical noteKAUST Repository Item: Exported on 2020-10-01
Acknowledgements: This research was supported by the grants from the New Energy
and Industrial Technology (NEDO), the Japan Science and Technology Agency
(CREST), and The Institute for Fermentation Organization, which were granted to S.O.
M.O. was supported by the grants from the Japan Society for the Promotion of Science,
the Union Tool Co., the Steel Foundation for Environmental Protection Technology, and
Yamaguchi Scholarship foundation. The authors acknowledge M. Waki and Y. Suwa for
valuable advices for isotopomer analysis of N2 gas, M. Morikawa for valuable
discussions and facilities for protein purification. Furthermore, M.O sincerely
appreciates B. Kartal and J.T. Keltjens for valuable discussions, advices and suggestions
to the present works.
ASJC Scopus subject areas
- Ecology, Evolution, Behavior and Systematics