NITRITE OXIDATION BY HETEROTROPHIC BACTERIA UNDER VARIOUS NUTRITIONALAND AEROBIC CONDITIONS

The nitrite transforming activities of heterotrophic bacteria from cul ture collections and isolates from activated sludge were studied under various nutritional and aerobic conditions. Among the 48 organisms te sted, 17 strains, many of which are reported as denitrification negati ves, consumed 1-5 mM of nitrite and accumulated corresponding amounts of nitrate. Twelve strains, many of which are denitrification-positive , consumed nitrite with the accumulation of less nitrate, while more t han 1 mM nitrite was consumed but little nitrate was accumulated by 14 strains, many of which are Enterobacteriaceae or lactic acid bacteria . None of the organisms formed significant nitrate in the medium witho ut nitrite, though a considerable amount of ammonia was also accumulat ed by most strains. Although the growth and nitrate accumulation of Ba cillus badius I-73 was affected by the concentrations of sodium nitrit e and peptone and by the culture volume, the amount of nitrate accumul ated was always proportional to that of the nitrite consumed. Intact c ells of B. badius I-73 produced almost the same amount of nitrate as t he decrease in nitrite. On the other hand, in B. subtilis I-41, a deni trification-positive isolate, the ratio of the amount of nitrate accum ulated to that of nitrite consumed varied from 0-100% depending on the culture conditions.