[Antibiotic formation in N-nitrosomethylbiuret exposure at different stages of conidium initiation in Penicillium chrysogenum, a producer of penicillin].

Survival and variation of strain 9741 of P. chrysogenum treated with N-nitroso-N-methyl biuret (NMB) at various stages of conidia initiation were studied. It was shown that the interval between the minimum and maximum levels of the conidia sensitivity to NMB was equal to 80 minutes, which corresponded to the period of DNA replication in the culture. When preliminary incubated conidia were subjected to the treatment, the frequency of the variants with higher potency increased as compared to the treatment of air-dried conidia. The variation coefficient increased, when conidia were treated with the mutagen after preliminary incubation for 80 or 100 minutes. This may be used for increasing the efficacy of directed improvement of the culture.