Metabolites Produced by Kaistia sp. 32K Promote Biofilm Formation in Coculture with Methylobacterium sp. ME121.

Previously, we reported that the coculture of motileMethylobacteriumsp. ME121 and non-motileKaistiasp. 32K, isolated from the same soil sample, displayed accelerated motility of strain ME121 due to an extracellular polysaccharide (EPS) produced by strain 32K. Since EPS is a major component of biofilms, we aimed to investigate the biofilm formation in cocultures of the two strains. The extent of biofilm formation was measured by a microtiter dish assay with the dye crystal violet. A significant increase in the amount of biofilm was observed in the coculture of the two strains, as compared to that of the monocultures, which could be due to a metabolite produced by strain 32K. However, in the coculture with strain 32K, usingEscherichia coliorPseudomonas aeruginosa, there was no difference in the amount of biofilm formation as compared with the monoculture. Elevated biofilm formation was also observed in the coculture of strain ME121 withKaistia adipata, which was isolated from a different soil sample.Methylobacterium radiotolerans, isolated from another soil sample, showed a significant increase in biofilm formation when cocultured withK. adipata, but not with strain 32K. We also found that the culture supernatants of strains 32K andK. adipataaccelerated the motility of strains ME121 andM. radiotolerans, wherein culture supernatant ofK. adipatasignificantly increased the motility ofM. radiotolerans, as compared to that by the culture supernatant of strain 32K. These results indicated that there was a positive relationship between accelerated motility and increased biofilm formation inMethylobacteriumspp. This is the first study to report that the metabolites fromKaistiaspp. could specifically modulate the biofilm-forming ability ofMethylobacteriumspp.Methylobacteriumspp. biofilms are capable of inhibiting the biofilm formation of mycobacteria, which are opportunistic pathogens that cause problems in infectious diseases. Thus, the metabolites from the culture supernatant ofKaistiaspp. have the potential to contribute to the environment in which increased biofilm production of Methylobacterium is desired.