ABSTRACT
A Gram-stain-negative, aerobic, non-motile and coccoid methanotroph, strain IM1T, was isolated from hot spring soil. Cells of strain IM1T were catalase-negative, oxidase-positive and displayed a characteristic intracytoplasmic membrane arrangement of type I methanotrophs. The strain possessed genes encoding both membrane-bound and soluble methane monooxygenases and grew only on methane or methanol. The strain was capable of growth at temperatures between 15 and 48 °C (optimum, 30-45 °C) and pH values between pH 4.8 and 8.2 (optimum, pH 6.2-7.0). Based on phylogenetic analysis of 16S rRNA gene and PmoA sequences, strain IM1T was demonstrated to be affiliated to the genus Methylococcus. The 16S rRNA gene sequence of this strain was most closely related to the sequences of an uncultured bacterium clone FD09 (100â%) and a partially described cultured Methylococcus sp. GDS2.4 (99.78â%). The most closely related taxonomically described strains were Methylococcus capsulatus TexasT (97.92â%), Methylococcus capsulatus Bath (97.86â%) and Methyloterricola oryzae 73aT (94.21â%). Strain IM1T shared average nucleotide identity values of 85.93 and 85.62â% with Methylococcus capsulatus strains TexasT and Bath, respectively. The digital DNA-DNA hybridization value with the closest type strain was 29.90â%. The DNA G+C content of strain IM1T was 63.3âmol% and the major cellular fatty acids were C16â:â0 (39.0â%), C16â:â1 ω7c (24.0â%), C16â:â1 ω6c (13.6â%) and C16â:â1 ω5c (12.0â%). The major ubiquinone was methylene-ubiquinone-8. On the basis of phenotypic, genetic and phylogenetic data, strain IM1T represents a novel species of the genus Methylococcus for which the name Methylococcus geothermalis sp. nov. is proposed, with strain IM1T (=JCM 33941T=KCTC 72677T) as the type strain.
Subject(s)
Hot Springs/microbiology , Methylococcus/classification , Phylogeny , Soil Microbiology , Bacterial Typing Techniques , Base Composition , DNA, Bacterial/genetics , Fatty Acids/chemistry , Methylococcus/isolation & purification , Nucleic Acid Hybridization , Oxygenases/genetics , RNA, Ribosomal, 16S/genetics , Republic of Korea , Sequence Analysis, DNA , Ubiquinone/chemistryABSTRACT
Methanotrophs were enriched and isolated from polluted environments in Canada and Germany. Enrichments in low copper media were designed to specifically encourage growth of soluble methane monooxygenase (sMMO) containing organisms. The 10 isolates were characterized physiologically and genetically with one type I and nine type II methanotrophs being identified. Three key genes: 16S rRNA; pmoA and mmoX, encoding for the particulate and soluble methane monooxygenases respectively, were cloned from the isolates and sequenced. Phylogenetic analysis of these sequences identified strains, which were closely related to Methylococcus capsulatus, Methylocystis sp., Methylosinus sporium and Methylosinus trichosporium. Diversity of sMMO-containing methanotrophs detected in this and previous studies was rather narrow, both genetically and physiologically, suggesting possible constraints on genetic diversity of sMMO due to essential conservation of enzyme function.