Biodiversity of methylotrophic microbial communities and their potential role in mitigation of abiotic stresses in plants

Methylotrophic bacterial community is very important group of bacteria utilizing reduced carbon compounds and plays significant role in plant growth promotion (PGP), crop yield and soil fertility for sustainable agriculture. Abiotic and biotic stresses are very important factors affecting PGP in agriculture. A vast number of microbial communities play an important role in abiotic stress tolerance. The PGP methylotrophic microbes have been reported well enough to mitigate different types of biotic and abiotic stresses. The abiotic stress tolerance was well documented by several methylotrophic bacterial communities such as Hyphomicrobium, Methylarcula, Methylobacillus, Methylobacterium, Methylocapsa, Methylocella, Methyloferula, Methylohalomonas, Methylomonas, Methylophilus, Methylopila, Methylosinus, Methylotenera, Methylovirgula and Methylovorus. The abiotic stress tolerance ability of different methylotrophs and their colonization in different parts of plants under severe low temperature, high temperature, drought and salt stress conditions have been investigated in various studies. The methylotrophic communities help in proliferation of plant directly through solubilization of phosphorus, potassium and zinc, production of phytohormones viz., auxins and cytokinins; production of Fe-chelating compound, biological nitrogen fixation and ACC-deaminase activities or indirectly through productions of ammonia, siderophores and secondary metabolites. The auxin and cytokinin secreted by methylotrophs influence seed germination and plant root growth and help plants to endure water stress. On the plant surface, the abundant methylotrophs exude osmo-protectants such as sugars and alcohols which ultimately help to protect the plants from desiccation and excessive radiations. The utilisation of these potent methylotrophic strains may facilitate proper crop production, PGP by ameliorating abiotic stresses.