By using these and other markers such as phospholipid fatty acids, the community structures of MOB have been intensively investigated in various types of ecosystems, mainly targeting type I and type II MOB.Ĭonsidering their unique function, MOB may play important roles in the water columns of freshwater lake ecosystems.
The pmoA gene encoding the α-subunit of this enzyme has been widely used as a marker to detect and identify MOB, along with the 16S rRNA gene. Especially, the particulate methane monooxygenase is found in most of the known MOB. Methane oxidation by all known MOB is mediated by monooxygenases, in contrast to the reverse methanogenesis pathway used by methane-oxidizing archaea.
oxyfera’-like bacteria detected in natural environments have been regarded as the MOB responsible for nitrite-dependent methane oxidation 9, 10, 11, 12. oxyfera’ and its relatives has been observed consistently in methane-oxidizing enrichment cultures established under anoxic nitrite-reducing conditions 5, 6, 7, 8, 9. oxyfera’ has the notable ability to produce oxygen from nitrite, which enables nitrite-dependent methane oxidation without an external supply of oxygen 4. Members of this group are recognized as ‘ Candidatus Methylomirabilis oxyfera’ and its close relatives, belonging to the candidate phylum NC10 3, 4. The fourth group has no representative isolated in pure culture. The third group, MOB in the phylum Verrucomicrobia, is extremely acidophilic and the family Methylacidiphilaceae was proposed to encompass this group 2. Type II MOB species belong to the families Methylocystaceae and Beijerinckiaceae. Most type I MOB are members of the family Methylococcaceae, but the family Methylothermaceae, was recently proposed 1. These 2 groups are also referred to as type I and type II, respectively. Two of these MOB groups, belonging to the classes Gammaproteobacteria and Alphaproteobacteria in the phylum Proteobacteria, have been well characterized. This ability is observed only in restricted lineages of prokaryotes and 4 major phylogenetic groups of MOB are currently known. Methane-oxidizing bacteria (MOB) are capable of gaining energy from the oxidation of the simplest hydrocarbon, methane. This is the first study to demonstrate that close relatives of the nitrite reducer can be major component of planktonic MOB community which may affect carbon flow in aquatic ecosystems. oxyfera’-like organisms in deep water was confirmed by catalyzed reporter deposition–fluorescence in situ hybridization, in which cells stained with a specific probe accounted for 16% of total microbial cells.
The presence of 3 groups of MOB in deep water was also shown by a cloning analysis of the pmoA gene encoding particulate methane monooxygenase. The last group, which consists of close relatives of the nitrite reducer ‘ Candidatus Methylomirabilis oxyfera’, was frequently detected in the clone libraries of deep-water environments. The groups belonged to the class Gammaproteobacteria, the class Alphaproteobacteria and the candidate phylum NC10.
Three groups of phylogenetically distinct MOB were detected in the clone libraries of polymerase chain reaction products obtained with universal primers. Bacterial community structure was investigated through the analysis of the 16S rRNA gene. In this study, the community structure of planktonic MOB was investigated in a subtropical reservoir. Methane-oxidizing bacteria (MOB) gain energy from the oxidation of methane and may play important roles in freshwater ecosystems.
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