Nitrite formation from organic nitrogen by Streptomyces antibioticus supporting bacterial cell growth and possible...

The actinomycete Streptomyces antibioticus was shown to produce nitrite (NO-(2)) and ammonium (NH+(4)]) when aerobically incubated in an organic nitrogen-rich medium. The production of NO-(2) was synchronized with rapid cell growth, whereas most NH+(4)] was produced after cell proliferation had ceased. Intracellular formation of nitric oxide (NO) was also observed during the incubation. The production of these inorganic nitrogen compounds along with cell growth was prevented by several enzyme inhibitors (of nitric oxide synthase or nitrate reductase) or glucose. Distinct, membrane-bound nitrate reductase was induced in the NO-(2)-producing cells. Tungstate (a potent inhibitor of this enzyme) prevented the NO-(2) production and cell growth, whereas it did not prevent the NO formation. These results revealed the occurrence of novel nitrogen metabolic pathway in S. antibioticus forming NO-(2) from organic nitrogen by which rapid cell growth is possible. NO synthase, NO dioxygenase (flavohemoglobin), and dissimilatory nitrate reductase are possible enzymes responsible for the NO-(2) formation.