FIG. 3.

Growth of E. coli RK 4353 and an E. coli RK 4353 mutant lacking all three known nitrate reductase enzymes determined by monitoring viable counts. The bacteria were first grown at pH 7 with sodium nitrate (10 mM NaNO₃). After 20 h the culture was transferred (and thereby diluted 1/10) to acidified urine (pH 5.0) containing 10 mM ascorbic acid, and bacterial growth was again monitored. Data are means ± standard deviations (n = 5).