1980 Volume 26 Issue 3 Pages 223-228
By applying the co-mutation procedure, 258 mutants unable to reduce nitrate were isolated in Streptomyces coelicolor A3 (2) among hisA+ revertants induced by nitrosoguanidine (MNNG). Of these, 82 were isolated as temperature-sensitive mutants (ammtps) at the non-permissive temperature (39°).
On the basis of their growth pattern, the amm co-mutants could be distinguished as falling into two main classes: 70 percent (ammA) were unable to utilize nitrite as a nitrogen source, while the remaining 30 percent (ammB) were able to reduce it.
Finally, by using a functional allelism test based on heterokaryon formation in mixed cultures, the ammA and ammB classes of co-mutants were attributed to three and two different complementation groups (cistrons), respectively.
