RT Journal Article SR Electronic(1) A1 Kozak, Witold A1 Rajchert-Trzpil, Marianna A1 Dobrzański, Władysław T.YR 1974 T1 The Effect of Proflavin, Ethidium Bromide and an Elevated Temperature on the Appearance of Nisin-negative Clones in Nisin-producing Strains of Streptococcus lactis JF Microbiology, VO 83 IS 2 SP 295 OP 302 DO https://doi.org/10.1099/00221287-83-2-295 PB Microbiology Society, SN 1465-2080, AB SUMMARY In some nisin-producing strains of Streptococcus lactis, clones which were permanently incapable of producing nisin (Nis−) appeared spontaneously with a frequency of 0·03 to 0·82 %. Treatment with proflavin (Pro), ethidium bromide (EB) or at a temperature of 40 °C increased the number of such clones. In one strain 78 % of cells became Nis− after treatment with Pro. Treatment with nitrosoguanidine did not reverse the effect of Pro or EB. There was no evidence that Pro or EB selected spontaneously-occurring Nis− clones. These observations suggest that the gene(s) responsible for nisin production in some S. lactis strains may be located on a plasmid, but further investigation is required to confirm this., UL https://www.microbiologyresearch.org/content/journal/micro/10.1099/00221287-83-2-295