著者

Shun Kobayashi Daisuke Hira Keitaro Yoshida Masanori Toyofuku Yosuke Shida Wataru Ogasawara Takashi Yamaguchi Nobuo Araki Mamoru Oshiki

出版者

Japanese Society of Microbial Ecology · The Japanese Society of Soil Microbiology

雑誌

Microbes and Environments (ISSN:13426311)

巻号頁・発行日

pp.ME18058, (Released:2018-10-12)

被引用文献数

35

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Aerobic ammonia-oxidizing archaea (AOA) play a crucial role in the global nitrogen cycle by oxidizing ammonia to nitrite, and nitric oxide (NO) is a key intermediate in AOA for sustaining aerobic ammonia oxidation activity. We herein heterologously expressed the NO-forming, copper-containing, dissimilatory nitrite reductase (NirK) from Nitrososphaera viennensis and investigated its enzymatic properties. The recombinant protein catalyzed the reduction of 15NO2– to 15NO, the oxidation of hydroxylamine (15NH2OH) to 15NO, and the production of 14-15N2O from 15NH2OH and 14NO2–. To the best of our knowledge, the present study is the first to document the enzymatic properties of AOA NirK.

著者

Yuga Hirakata Mamoru Oshiki Kyohei Kuroda Masashi Hatamoto Kengo Kubota Takashi Yamaguchi Hideki Harada Nobuo Araki

出版者

日本微生物生態学会 / 日本土壌微生物学会 / Taiwan Society of Microbial Ecology / 植物微生物研究会

雑誌

Microbes and Environments (ISSN:13426311)

巻号頁・発行日

pp.ME16067, (Released:2016-07-12)

被引用文献数

22

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Predation by protists is top-down pressure that regulates prokaryotic abundance, community function, structure, and diversity in natural and artificial ecosystems. Although the effects of predation by protists have been studied in aerobic ecosystems, they are poorly understood in anoxic environments. We herein studied the influence of predation by Metopus and Caenomorpha ciliates—ciliates frequently found in anoxic ecosystems—on prokaryotic community function, structure, and diversity. Metopus and Caenomorpha ciliates were cocultivated with prokaryotic assemblages (i.e., anaerobic granular sludge) in an up-flow anaerobic sludge blanket (UASB) reactor for 171 d. Predation by these ciliates increased the methanogenic activities of granular sludge, which constituted 155% of those found in a UASB reactor without the ciliates (i.e., control reactor). Sequencing of 16S rRNA gene amplicons using Illumina MiSeq revealed that the prokaryotic community in the UASB reactor with the ciliates was more diverse than that in the control reactor; 2,885–3,190 and 2,387–2,426 operational taxonomic units (>97% sequence similarities), respectively. The effects of predation by protists in anaerobic engineered systems have mostly been overlooked, and our results show that the influence of predation by protists needs to be examined and considered in the future for a better understanding of prokaryotic community structure and function.

著者

Mamoru Oshiki Lin Gao Lei Zhang Satoshi Okabe

出版者

Japanese Society of Microbial Ecology / Japanese Society of Soil Microbiology / Taiwan Society of Microbial Ecology / Japanese Society of Plant Microbe Interactions / Japanese Society for Extremophiles

雑誌

Microbes and Environments (ISSN:13426311)

巻号頁・発行日

vol.37, no.2, pp.ME21092, 2022 (Released:2022-04-12)

参考文献数

47

被引用文献数

1

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Anammox bacteria produce N2 gas by oxidizing NH4+ with NO2–, and hydroxylamine (NH2OH) is a potential intermediate of the anammox process. N2 gas production occurs when anammox bacteria are incubated with NH2OH only, indicating their capacity for NH2OH disproportionation with NH2OH serving as both the electron donor and acceptor. Limited information is currently available on NH2OH disproportionation by anammox bacteria; therefore, the stoichiometry of anammox bacterial NH2OH disproportionation was examined in the present study using 15N-tracing techniques. The anammox bacteria, Brocadia sinica, Jettenia caeni, and Scalindua sp. were incubated with the addition of 15NH2OH, and the production of 15N-labeled nitrogenous compounds was assessed. The anammox bacteria tested performed NH2OH disproportionation and produced 15-15N2 gas and NH4+ as reaction products. The addition of acetylene, an inhibitor of the anammox process, reduced the activity of NH2OH disproportionation, but not completely. The growth of B. sinica by NH2OH disproportionation (–240.3‍ ‍kJ mol NH2OH–1 under standard conditions) was also tested in 3 up-flow column anammox reactors fed with 1) 0.7‍ ‍mM NH2OH only, 2) 0.7‍ ‍mM NH2OH and 0.5‍ ‍mM NH4+, and 3) 0.7‍ ‍mM NH2OH and 0.5‍ ‍mM NO2–. NH2OH consumption activities were markedly reduced after 7‍ ‍d of operation, indicating that B. sinica was unable to maintain its activity or biomass by NH2OH disproportionation.

著者

Mamoru Oshiki Yoshihiro Takaki Miho Hirai Takuro Nunoura Atsushi Kamigaito Satoshi Okabe

出版者

Japanese Society of Microbial Ecology / Japanese Society of Soil Microbiology / Taiwan Society of Microbial Ecology / Japanese Society of Plant Microbe Interactions / Japanese Society for Extremophiles

雑誌

Microbes and Environments (ISSN:13426311)

巻号頁・発行日

vol.37, no.3, pp.ME22017, 2022 (Released:2022-07-09)

参考文献数

57

被引用文献数

5

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Anaerobic ammonium-oxidizing (anammox) bacteria are slow-growing and fastidious bacteria, and limited numbers of enrichment cultures have been established. A metagenomic ana­lysis of our 5 established anammox bacterial enrichment cultures was performed in the present study. Fourteen high-quality metagenome-assembled genomes (MAGs) were obtained, including those of 5 anammox Planctomycetota (Candidatus Brocadia, Ca. Kuenenia, Ca. Jettenia, and Ca. Scalindua), 4 Bacteroidota, and 3 Chloroflexota. Based on the gene sets of metabolic pathways involved in the degradation of polymeric substances found in Chloroflexota and Bacteroidota MAGs, they are expected to be scavengers of extracellular polymeric substances and cell debris.

著者

Mamoru Oshiki Yuka Toyama Toshikazu Suenaga Akihiko Terada Yasuhiro Kasahara Takashi Yamaguchi Nobuo Araki

出版者

Japanese Society of Microbial Ecology / Japanese Society of Soil Microbiology / Taiwan Society of Microbial Ecology / Japanese Society of Plant Microbe Interactions / Japanese Society for Extremophiles

雑誌

Microbes and Environments (ISSN:13426311)

巻号頁・発行日

vol.37, no.2, pp.ME21090, 2022 (Released:2022-04-12)

参考文献数

61

被引用文献数

7

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Agricultural soil is the primary N2O sink limiting the emission of N2O gas into the atmosphere. Although Gemmatimonadetes bacteria are abundant in agricultural soils, limited information is currently available on N2O reduction by Gemmatimonadetes bacteria. Therefore, the effects of pH and temperature on N2O reduction activities and affinity constants for N2O reduction were examined by performing batch experiments using an isolate of Gemmatimonadetes bacteria, Gemmatimonas aurantiaca (NBRC100505T). G. aurantiaca reduced N2O at pH 5–9 and 4–50°C, with the highest activity being observed at pH 7 and 30°C. The affinity constant of G. aurantiaca cells for N2O was 4.4‍ ‍μM. The abundance and diversity of the Gemmatimonadetes 16S rRNA gene and nosZ encoding nitrous oxide reductase in agricultural soil samples were also investigated by quantitative PCR (qPCR) and amplicon sequencing ana­lyses. Four N2O-reducing agricultural soil samples were assessed, and the copy numbers of the Gemmatimonadetes 16S rRNA gene (clades G1 and G3), nosZ DNA, and nosZ mRNA were 8.62–9.65×108, 5.35–7.15×108, and 2.23–4.31×109 copies (g dry soil)–1, respectively. The abundance of the nosZ mRNA of Gemmatimonadetes bacteria and OTU91, OUT332, and OTU122 correlated with the N2O reduction rates of the soil samples tested, suggesting N2O reduction by Gemmatimonadetes bacteria. Gemmatimonadetes 16S rRNA gene reads affiliated with OTU4572 and OTU3759 were predominant among the soil samples examined, and these Gemmatimonadetes OTUs have been identified in various types of soil samples.

著者

Shun Kobayashi Daisuke Hira Keitaro Yoshida Masanori Toyofuku Yosuke Shida Wataru Ogasawara Takashi Yamaguchi Nobuo Araki Mamoru Oshiki

出版者

Japanese Society of Microbial Ecology · The Japanese Society of Soil Microbiology

雑誌

Microbes and Environments (ISSN:13426311)

巻号頁・発行日

vol.33, no.4, pp.428-434, 2018 (Released:2018-12-28)

参考文献数

47

被引用文献数

1 35

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Aerobic ammonia-oxidizing archaea (AOA) play a crucial role in the global nitrogen cycle by oxidizing ammonia to nitrite, and nitric oxide (NO) is a key intermediate in AOA for sustaining aerobic ammonia oxidation activity. We herein heterologously expressed the NO-forming, copper-containing, dissimilatory nitrite reductase (NirK) from Nitrososphaera viennensis and investigated its enzymatic properties. The recombinant protein catalyzed the reduction of 15NO2− to 15NO, the oxidation of hydroxylamine (15NH2OH) to 15NO, and the production of 14–15N2O from 15NH2OH and 14NO2−. To the best of our knowledge, the present study is the first to document the enzymatic properties of AOA NirK.

著者

Yuga Hirakata Mamoru Oshiki Kyohei Kuroda Masashi Hatamoto Kengo Kubota Takashi Yamaguchi Hideki Harada Nobuo Araki

出版者

Japanese Society of Microbial Ecology · The Japanese Society of Soil Microbiology

雑誌

Microbes and Environments (ISSN:13426311)

巻号頁・発行日

vol.30, no.4, pp.335-338, 2015 (Released:2015-12-22)

参考文献数

22

被引用文献数

11 23

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The aim of the present study was to investigate the prokaryotic community structure of the anaerobic ciliate, Metopus sp. using rRNA sequencing, fluorescence in situ hybridization (FISH), and transmission electron microscopy (TEM). Metopus sp. was physically separated from anaerobic granular sludge in a domestic wastewater treatment plant and anoxically cultivated for 7 d. 16S rRNA gene sequences from the prokaryotes Methanoregula boonei and Clostridium aminobutyricum were abundantly detected in Metopus ciliates. The FISH analysis using the oligonucleotide probes Mg1200b and Cla568 demonstrated that these prokaryotes were localized within Metopus cells. These results identify M. boonei- and C. aminobutyricum-like prokaryotes as novel endosymbionts of Metopus ciliates.