Methylotrophs

Methylotrophs are a diverse group of bacteria and some archaea that can grow on reduced single-carbon compounds as their principal sources of carbon and energy. The group includes methanotrophs, which oxidize methane, and non-methanotrophic methylotrophs that utilize substrates such as methanol, methylamine, formate, or formaldehyde. They contribute to the global carbon cycle by transforming C1 compounds into biomass and other metabolites.

Metabolism in methylotrophs typically begins with the oxidation of a one-carbon substrate. In methanotrophs, methane is oxidized by methane monooxygenase to methanol, which is then converted to formaldehyde by methanol dehydrogenase. Formaldehyde may be assimilated into biomass or further oxidized to formate and CO2 for energy. Two major carbon-assimilation pathways operate in methylotrophs: the ribulose Monophosphate (RuMP) pathway and the serine cycle. Some methylotrophs can also fix CO2 via the Calvin-Benson-Bassham cycle. Key cofactors and enzymes, such as pyrroloquinoline quinone (PQQ) in methanol oxidation, support the unique energy and carbon economies of these organisms.

Ecology and significance: Methylotrophs are found in soils, freshwater and marine environments, plant surfaces, and engineered systems. They play important roles in methane mitigation and in recycling C1 compounds, linking methanogenesis with broader microbial food webs. They can be free-living or associated with plants or sediments and may interact with other microbes in syntrophic communities.

Examples and applications: Notable methylotrophic taxa include genera such as Methylobacter, Methylomonas, Methylomicrobium, and Methylophilus. Methylotrophs have potential applications in bioremediation, methane or methanol-based bioprocesses, and the production of value-added compounds through C1 metabolism.