Emergence of Methylobacterium spp. as Potential Organism in Agroecosystems

Methylobacterium spp. includes a group of stringently aerobic, Gram-negative, pink-pigmented, facultatively methylotrophs (PPFM) belonging to α-proteobacteria and are capable of growing on one-carbon compounds, such as formate, formaldehyde, methanol and methylamine or sometimes on multi-carbon compounds like diethyl ether and trimethyl amines. Significance of these bacteria for plant-growth promotion by the possible mechanisms include production of phytohormones, IAA, cytokinins, ACC-deaminase and perform nitrogen metabolism by means of bacterial urease, establish efficient nitrogen (N2)-fixing symbioses by nodulating legume roots; production of exopolysaccharides (EPS) and Poly-β-hydroxybutyrate (PHB) accumulation and abiotic stress endurance. These organisms induce systemic resistance by production of siderophores and proteins like phenylalanine ammonia lyase, peroxidase, chitinase and β-1,3-glucanase and phenolic compounds. On the other hand, they also promote the biodegradation of polycyclic aromatic hydrocarbon (PAH). In spite of their plant-growth promotional traits, commercialization of the Methylobacterium strains as bioinoculant have been hindered constantly.