title: Methylothermus thermalis gen. nov., sp. nov., a novel moderately thermophilic obligate methanotroph from a hot spring in Japan.
abstract: A novel moderately thermophilic methanotroph, strain MYHT(T), was isolated from a hot spring in Japan. The isolate grew on methane or methanol at 37-67 degrees C, and optimally at 57-59 degrees 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 MYHT(T) 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 6.5-7.5 (optimum pH 6.8) and in up to 3% NaCl (optimum 0.5-1% NaCl). Phylogenetic analysis based on 16S rRNA gene sequence analysis indicated that strain MYHT(T) is most closely related to the thermophilic undescribed methanotroph 'Methylothermus' HB (91% identity) and the novel halophilic methanotroph Methylohalobius crimeensis 10Ki(T) (90% identity). Comparative sequence analysis of particulate methane monooxygenase (pmoA) genes also confirmed the clustering of strain MYHT(T) with 'Methylothermus' HB and Methylohalobius crimeensis 10Ki(T) (98 and 92% derived amino acid sequence identity, respectively). The DNA G+C content was 62.5 mol%. The major cellular fatty acids were C(16:0) (37.2%) and C(18:1)omega9c (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 MYHT(T) as the type strain (=VKM B-2345(T)=IPOD FERM P-19714(T)).
authors.affiliation: Energy and Technology Laboratories, Osaka Gas Co., Ltd, 6-19-9 Torishima Konohana-ku, Osaka 554-0051, Japan.
authors.forename: Jun
authors.initials: J
authors.lastname: Tsubota
authors.affiliation: G. K. Skryabin Institute of Biochemistry and Physiology of Microorganisms, Russian Academy of Sciences, 142290 Pushchino, Moscow Region, Russia.
authors.forename: Bulat Ts
authors.initials: BT
authors.lastname: Eshinimaev
authors.affiliation: G. K. Skryabin Institute of Biochemistry and Physiology of Microorganisms, Russian Academy of Sciences, 142290 Pushchino, Moscow Region, Russia.
authors.forename: Valentina N
authors.initials: VN
authors.lastname: Khmelenina
authors.affiliation: G. K. Skryabin Institute of Biochemistry and Physiology of Microorganisms, Russian Academy of Sciences, 142290 Pushchino, Moscow Region, Russia.
authors.forename: Yuri A
authors.initials: YA
authors.lastname: Trotsenko
mesh_terms: D015373:Bacterial Typing Techniques; D004269:DNA, Bacterial / Q000032:analysis; D005838:Genotype; D045482:Hot Springs / Q000382:microbiology*; D006358:Hot Temperature; D007564:Japan; D008697:Methane / Q000378:metabolism*; D000432:Methanol / Q000378:metabolism*; D008772:Methylococcaceae / Q000145:classification* / Q000235:genetics / Q000302:isolation & purification / Q000502:physiology; D008969:Molecular Sequence Data; D010105:Oxygenases / Q000235:genetics; D010641:Phenotype; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D017422:Sequence Analysis, DNA
chemical_list: D004269:DNA, Bacterial; D012336:RNA, Ribosomal, 16S; D010105:Oxygenases; C021555:methane monooxygenase; D008697:Methane; D000432:Methanol