Methylobacter

Methylobacterium, commonly referred to as Methylobacter, is a genus of Gram-negative, rod-shaped bacteria that are pink-pigmented due to carotenoid production. They are facultative methylotrophs, meaning they can use one-carbon compounds such as methanol as carbon and energy sources, although they can also grow on multicarbon substrates. Taxonomically, Methylobacterium belongs to the Beijerinckiaceae family within the Alphaproteobacteria; in recent classifications several species formerly placed in Methylobacterium have been reassigned to the genus Methylorubrum.

Ecology and habitat: Methylobacterium species are widespread in soil and freshwater environments and are particularly common on plant surfaces (the phyllosphere). Many isolates function as endophytes or epiphytes in association with diverse host plants. They are adapted to nutrient-limited conditions and can utilize methanol emitted from plant tissues.

Metabolism and physiology: As methylotrophs, these bacteria oxidize methanol via methanol dehydrogenases, often MxaFI or XoxF, with PQQ as a cofactor. Formaldehyde produced in this process is assimilated through pathways such as the serine cycle. They generally tolerate oxygen and can use a range of substrates beyond methanol.

Ecological and applied relevance: Methylobacterium species are studied for their plant-associated interactions, including potential growth promotion and nutrient acquisition, as well as biocontrol aspects. Their methylotrophic metabolism makes them of interest for biotechnological applications, including methanol-based bioconversion and the production of value-added compounds. Genomic and comparative studies continue to refine understanding of their diversity, ecology, and capabilities.