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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 H-2 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.