Effect of mixed culture on Nitrosomonas europaea simulated by uptake and utilization of pyruvate

Clark, Connie (University of Minnesota, Minneapolis), and E. L. Schmidt. Effect of mixed culture on Nitrosomonas europaea simulated by uptake and utilization of pyruvate. J. Bacteriol. 91:367-373. 1966.-Contamination of a 5-liter culture of Nitrosomonas europaea resulted in enhanced nitrite formation as compared with pure cultures. The dominant contaminant, a yellow-pigmented, heterotrophic bacterium, was isolated and studied both in pure culture and in deliberate mixture with N. europaea. Growth of N. europaea was stimulated in mixed cultures with the heterotrophic isolate to varying degrees, apparently depending on the age and density of autotrophic inocula. Mixed culture stimulation of N. europaea was evidenced only by a shortened lag phase, since post-lag phase growth of the autotroph was equivalent in both pure and mixed cultures. The heterotrophic component had a nutritional requirement for amino acids when grown on simple media; presumably, in the mixed culture system, the heterotroph was provided with amino acids synthesized by the autotroph. The mixed culture effect was reproduced in all essential features by the addition of sodium pyruvate to the nitrification medium. Pure cultures of N. europaea were shown to incorpo...Continue Reading