Potentials, Utilization, and Bioengineering of Plant Growth-Promoting Methylobacterium for Sustainable Agriculture

Plant growth-promoting bacteria (PGPB) have great potential to provide economical and sustainable solutions to current agricultural challenges. The Methylobacteria which are frequently present in the phyllosphere can promote plant growth and development. The Methylobacterium genus is composed mostly of pink-pigmented facultative methylotrophic bacteria, utilizing organic one-carbon compounds as the sole carbon and energy source for growth. Methylobacterium spp. have been isolated from diverse environments, especially from the surface of plants, because they can oxidize and assimilate methanol released by plant leaves as a byproduct of pectin formation during cell wall synthesis. Members of the Methylobacterium genus are good candidates as PGPB due to their positive impact on plant health and growth; they provide nutrients to plants, modulate phytohormone levels, and protect plants against pathogens. In this paper, interactions between Methylobacterium spp. and plants and how the bacteria promote crop growth is reviewed. Moreover, the following examples of how to engineer microbiomes of plants using plant-growth-promoting Methylobacterium are discussed in the present review: introducing external Methylobacterium spp. to plants, introducing functional genes or clusters to resident Methylobacterium spp. of crops, and enhancing the abilities of Methylobacterium spp. to promote plant growth by random mutation, acclimation, and engineering.