The physiological potential of anammox bacteria as revealed by their core genome structure |
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Authors: | Takashi Okubo Atsushi Toyoda Kohei Fukuhara Ikuo Uchiyama Yuhki Harigaya Megumi Kuroiwa Takuma Suzuki Yuka Murakami Yuichi Suwa Hideto Takami |
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Institution: | 1. Marine Microbiology, Atmosphere and Ocean Research Institute, The University of Tokyo, Kashiwa 277-8564, Japan;2. Comparative Genomics Laboratory, National Institute of Genetics, Mishima 411-8540, Japan;3. Department of Biological Sciences, Chuo University, Bunkyo, Tokyo 112-8851, Japan;4. Laboratory of Genome Informatics, National Institute for Basic Biology, National Institutes of Natural Sciences, Myodaiji, Okazaki 444-8585, Japan |
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Abstract: | We present here the second complete genome of anaerobic ammonium oxidation (anammox) bacterium, Candidatus (Ca.) Brocadia pituitae, along with those of a nitrite oxidizer and two incomplete denitrifiers from the anammox bacterial community (ABC) metagenome. Although reduction to NO is considered to be the first step in anammox, Ca. B. pituitae lacks nitrite reductase genes (nirK and nirS) responsible for this reaction. Comparative genomics of Ca. B. pituitae with Ca. Kuenenia stuttgartiensis and six other anammox bacteria with nearly complete genomes revealed that their core genome structure contains 1,152 syntenic orthologues. But nitrite reductase genes were absent from the core, whereas two other Brocadia species possess nirK and these genes were horizontally acquired from multiple lineages. In contrast, at least five paralogous hydroxylamine oxidoreductase genes containing candidate ones (hao2 and hao3) encoding another nitrite reductase were observed in the core. Indeed, these two genes were also significantly expressed in Ca. B. pituitae as in other anammox bacteria. Because many nirS and nirK genes have been detected in the ABC metagenome, Ca. B. pituitae presumably utilises not only NO supplied by the ABC members but also NO and/or NH2OH by self-production for anammox metabolism. |
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Keywords: | anammox metagenomics physiological potential core genome structure |
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