@article{mbs:/content/journal/micro/10.1099/00221287-13-3-561, author = "Sneath, P. H. A.", title = "Proof of the Spontaneity of a Mutation to Penicillinase Production in Bacillus cereus", journal= "Microbiology", year = "1955", volume = "13", number = "3", pages = "561-568", doi = "https://doi.org/10.1099/00221287-13-3-561", url = "https://www.microbiologyresearch.org/content/journal/micro/10.1099/00221287-13-3-561", publisher = "Microbiology Society", issn = "1465-2080", type = "Journal Article", abstract = "SUMMARY: A stable mutation in a strain of Bacillus cereus from penicillin sensitivity to penicillin resistance due to the production of large amounts of penicillinase is reported. By the velvet pad replicate technique this mutation has been shown to be a spontaneous event occurring in the absence of penicillin. Penicillin-resistant mutants were obtained and the penicillinase production proved, without ever bringing the cells into contact with the antibiotic. The mutation rate is about 3 × 10−8 mutations per bacterium per division.", }