Substrate selection as a possible strategy for amelioration of acid pH by Rhizobium leguminosarum biovar viciae

A possible mechanism for bacteria to ameliorate an unfavorably acidic external pH would be to select for catabolism of those substrates in a mixture that would alkalinize the medium. This hypothesis was tested with cultures of Rhizobium leguminosarum biovar viciae WSM710 grown at pH 7.0 or 5.5 on binary mixtures of glucose plus fumarate or glucose plus histidine. The results showed no significant increase in the absolute or relative utilization of the alkalinizing substrates (fumarate or histidine) at pH 5.5.