methylotroph

Methylotrophs are microorganisms that can grow on reduced one-carbon compounds (C1) as their sole source of carbon and energy, or use C1 substrates in addition to other carbon sources. Common C1 substrates include methanol, methylamine, formate, and formaldehyde; methane is used by a specialized subset known as methanotrophs. Methylotrophs encompass a diverse range of bacteria as well as some yeasts.

Metabolism in methylotrophs involves oxidation of C1 substrates to yield energy and reducing equivalents, followed by assimilation of carbon into biomass. Methanotrophs typically oxidize methane to methanol via methane monooxygenase, with formaldehyde as an intermediate. Other methylotrophs metabolize methanol, methylamine, or formate through dedicated enzymes such as methanol dehydrogenase and amine oxidases. Assimilation of C1 carbon into biomass is achieved through pathways such as the ribulose monophosphate (RuMP) pathway or the serine cycle, with some lineages utilizing the Calvin cycle or alternative routes.

Ecology and distribution: methylotrophs are found in a wide range of environments, including soil, freshwater, and marine systems, as well as the phyllosphere of plants and in associations with roots and fungi. They contribute to global carbon cycling by transforming methanol and other C1 compounds released by plants and microbial activity.

Examples and applications: well-studied bacterial methylotrophs include Methylobacterium, Methylophilus, and Hyphomicrobium, while methanotrophic genera include Methylococcus and Methylosinus. Methylotrophic yeasts such as Candida boidinii and Pichia pastoris are important in biotechnology for methanol-based expression systems. Applications include bioremediation, methane mitigation, and biotechnological production using C1 substrates.