[Effect of certain environmental factors on Bradyrhizobium japonicum]

Dependence of motility and chemotaxis was studied in two strains of Bradyrhizobium japonicum upon several environmental factors. In both strains, chemotaxis was found to increase with an increasing concentration of the attractant (glucose) to 5.6 x 10(-2) M. Both motility and chemotaxis reached their maximum in the two- to three-day cultures at neutral pH. The maximum motility of these bacteria occurred at 40 degrees C. The maximum values of chemotaxis in these microorganisms were, however, observed at 20-25 degrees C. Chemotaxis in acidic or alkaline media and at low temperatures was found to be markedly weaker. Nonoptimal values of these parameters in soil may be a limiting factor for the interaction of the given bacteria with soybean roots.