Methylotrophy

Methylotrophy is the ability of certain organisms to grow on reduced one-carbon compounds, or C1 substrates, as sole sources of carbon and energy. Common C1 substrates include methane, methanol, methylamine, and formate. Methylotrophs are found across bacteria, archaea, and some yeasts, and they play important roles in global carbon cycling and in biotechnological processes.

In methylotroph metabolism, oxidation of C1 substrates provides energy and reducing power, while formaldehyde often serves as a central intermediate that is then assimilated into biomass. Two main routes for carbon assimilation are the ribulose monophosphate (RuMP) pathway and the serine cycle. Methanotrophic bacteria, which oxidize methane, typically use methane monooxygenase to convert methane to methanol, followed by further oxidation to formaldehyde. Depending on the lineage, carbon is incorporated into cellular material via RuMP or the serine cycle.

Organisms are classified as methanotrophs (specializing in methane oxidation) and non-methanotrophic methylotrophs (which grow on methanol, methylamine, or other C1 substrates). Notable methanotrophs include members of the genera Methylococcus, Methylosinus, and Methylocystis, while Methylobacterium and Hyphomicrobium are examples of non-methanotrophic methylotrophs. Methylotrophs can be facultative, able to utilize C1 substrates as well as multicarbon compounds, or obligate, relying primarily on C1 substrates for growth.

Applications and importance include bioremediation of methane-rich environments, bioconversion of methanol to biomass or value-added products, and insights into carbon cycling in natural and engineered ecosystems.