The experiments were performed exactly as described
above for ammonium effect. The ntcA transcript is
expressed at basal levels when grown in nitrate-containing
medium and at maximal levels following N-depletion,
while it decreases when ammonium is supplied to the
N-depleted cultures (Fig. 7). The effects of nitrite and glutamine
on ntcA expression were more or less similar to that
of nitrate described above