Mgl2 Is a Hypothetical Methyltransferase Involved in Exopolysaccharide Production, Biofilm Formation, and Motility in bv. .

In this study, functional characterization of the gene located near the Pss-I exopolysaccharide biosynthesis region in bv. TA1 is described. The hypothetical protein encoded by the gene was found to be similar to methyltransferases (MTases). Protein homology and template-based modeling facilitated prediction of the Mgl2 structure, which greatly resembled class I MTases with a S-adenosyl-L-methionine-binding cleft. The Mgl2 protein was engaged in exopolysaccharide, but not lipopolysaccharide, synthesis. The deletion mutant produced exopolysaccharide comprised of only low molecular weight fractions, while overexpression of caused overproduction of exopolysaccharide with a normal low to high molecular weight ratio. The deletion of the gene resulted in disturbances in biofilm formation and a slight increase in motility in minimal medium. Red clover () inoculated with the mutant formed effective nodules, and the appearance of the plants indicated active nitrogen fixation. The gene was preceded by an active and strong promoter. Mgl2 was defined as an integral membrane protein and formed homodimers in vivo; however, it did not interact with Pss proteins encoded within the Pss-I region. The results are discussed in the context of the possible involvement of the newly described potential MTase in various metabolic traits, such as the exopolysaccharide synthesis and motility that are important for rhizobial saprophytic and symbiotic relationships.