Semiaerobic induction of a nitrate reductase activity in growing cultures of Rhodopseudomonas capsulata E1F1 containing NH 4 + ions as nitrogen source

Rhodopseudomonas capsulata E₁F₁ growing under chemo- or photoorganotrophic conditions shows nitrate reductase activity which:

1. Is not repressed by ammonium ions;
2. Is governed by the partial pressure of oxygen in the gas phase.

Upon induction of nitrate reductase activity under optimum conditions, and also in the presence of amonium ions, subsequent addition of nitrate does not result in nitrite production. The specific activity of the enzyme increases by a factor of 10, when the growth medium is supplemented by the addition of nitrate. The physiological role of this ammonium resistant activity is not known.