Int J Syst Evol Microbiol 55 (2005), 1877-1884; DOI 10.1099/ijs.0.63691-0
© 2005 International Union of Microbiological Societies
Methylothermus thermalis gen. nov., sp. nov., a novel moderately thermophilic obligate methanotroph from a hot spring in Japan
Jun Tsubota1,
Bulat Ts. Eshinimaev2,
Valentina N. Khmelenina2 and
Yuri A. Trotsenko2
1 Energy and Technology Laboratories, Osaka Gas Co., Ltd, 6-19-9 Torishima Konohana-ku, Osaka 554-0051, Japan
2 G. K. Skryabin Institute of Biochemistry and Physiology of Microorganisms, Russian Academy of Sciences, 142290 Pushchino, Moscow Region, Russia
Correspondence
Yuri A. Trotsenko
trotsenko{at}ibpm.pushchino.ru
A novel moderately thermophilic methanotroph, strain MYHTT, was isolated from a hot spring in Japan. The isolate grew on methane or methanol at 3767 °C, and optimally at 5759 °C. It was found to be a Gram-negative aerobe, with colourless colonies of non-motile coccoid cells, possessing type I intracytoplasmic membranes and regularly arranged surface layers of linear (p2) symmetry. Strain MYHTT expressed only the particulate methane monooxygenase and employed the ribulose monophosphate pathway for formaldehyde assimilation. It is a neutrophilic and halotolerant organism capable of growth at pH 6·57·5 (optimum pH 6·8) and in up to 3 % NaCl (optimum 0·51 % NaCl). Phylogenetic analysis based on 16S rRNA gene sequence analysis indicated that strain MYHTT is most closely related to the thermophilic undescribed methanotroph Methylothermus HB (91 % identity) and the novel halophilic methanotroph Methylohalobius crimeensis 10KiT (90 % identity). Comparative sequence analysis of particulate methane monooxygenase (pmoA) genes also confirmed the clustering of strain MYHTT with Methylothermus HB and Methylohalobius crimeensis 10KiT (98 and 92 % derived amino acid sequence identity, respectively). The DNA G+C content was 62·5 mol%. The major cellular fatty acids were C16 : 0 (37·2 %) and C18 : 1
9c (35·2 %) and the major polar lipids were phosphatidylethanolamine and phosphatidylglycerol. The major ubiquinone was Q-8. On the basis of comparative phenotypic and genotypic characteristics, a new genus and species, Methylothermus thermalis gen. nov., sp. nov., is proposed, with MYHTT as the type strain (=VKM B-2345T=IPOD FERM P-19714T).
Abbreviations: ICM, intracytoplasmic membrane; PLFA, phospholipid fatty acid; pMMO and sMMO, particulate and soluble methane monooxygenase, respectively; RuMP, ribulose monophosphate
The GenBank/EMBL/DDBJ accession numbers for the 16S rRNA gene sequence and partial sequence of the pmoA gene of Methylothermus thermalis strain MYHTT are AY829009 and AY829010, respectively.
A figure showing the oxidation and assimilation of 14C-methane by cells of strain MYHTT is available as supplementary material in IJSEM Online.
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Copyright © 2005 by the International Union of Microbiological Societies.