Oxygen protection of nitrogen fixation in free-living Azorhizobium caulinodans: the role of cytochrome aa.

The growth properties of Azorhizobium caulinodans wild-type and a cytochrome aa mutant strain, both growing with N as N source at fixed dissolved partial oxygen pressures in the range 0.5--4.0 kPa, were studied by making use of continuous cultures (chemostats and pH-auxostats) and transient cultures.