Abstract
Aerobic methane-oxidizing bacteria, or methanotrophs, play a crucial role in the global methane cycle. Their methane oxidation activity in various environmental settings has a great mitigation effect on global climate change. Alphaproteobacterial methanotrophs were among the first to be taxonomically characterized, nowadays unified in the Methylocystaceae and Beijerinckiaceae families. Originally thought to have an obligate growth requirement for methane and related one-carbon compounds as a source of carbon and energy, it was later shown that various alphaproteobacterial methanotrophs are facultative, able to grow on multi-carbon compounds such as acetate. Most recently, we expanded our knowledge of the metabolic versatility of alphaproteobacterial methanotrophs. We showed that Methylocystis sp. strain SC2 has the capacity for mixotrophic growth on H2 and CH4. This mini-review will summarize the change in perception from the long-held paradigm of obligate methanotrophy to today's recognition of alphaproteobacterial methanotrophs as having both facultative and mixotrophic capabilities.
Highlights
Methane (CH4) is the most abundant organic compound in the Earth’s atmosphere, and it is the second most importantMethanotrophs are a subset of a physiological group known as methylotrophs, microorganisms that grow on one-carbon compounds such as methanol and methylated amines
Thought to have an obligate growth requirement for methane and related one-carbon compounds as a source of carbon and energy, it was later shown that various alphaproteobacterial methanotrophs are facultative, able to grow on multi-carbon compounds such as acetate
Hydrogenase activities in proteobacterial methanotrophs have been shown to contribute reducing power for methane oxidation (Hanczar et al 2002), recycle endogenous hydrogen produced during nitrogen fixation (Chen et al 1987) and drive the nonproductive oxidation of chlorinated solvents in Methylosinus trichosporium OB3b (Shah et al 1995)
Summary
Methane (CH4) is the most abundant organic compound in the Earth’s atmosphere, and it is the second most importantMethanotrophs are a subset of a physiological group known as methylotrophs, microorganisms that grow on one-carbon compounds such as methanol and methylated amines. Thought to have an obligate growth requirement for methane and related one-carbon compounds as a source of carbon and energy, it was later shown that various alphaproteobacterial methanotrophs are facultative, able to grow on multi-carbon compounds such as acetate.
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