@article{mbs:/content/journal/micro/10.1099/00221287-27-1-155, author = "de Klerk, H. C. and Coetzee, J. N.", title = "The S-R Variation in Lactobacillus casei", journal= "Microbiology", year = "1962", volume = "27", number = "1", pages = "155-166", doi = "https://doi.org/10.1099/00221287-27-1-155", url = "https://www.microbiologyresearch.org/content/journal/micro/10.1099/00221287-27-1-155", publisher = "Microbiology Society", issn = "1465-2080", type = "Journal Article", abstract = "SUMMARY: Colonies of four strains of Lactobacillus casei var. casei and three strains of L. casei var. rhamnosus investigated may develop rough outgrowths while growing on a medium containing no fermentable carbohydrate. Colonies do not form visible outgrowths when growing on the same medium containing more than 0ยท5% (w/v) glucose. Rough elements may be present in the latter colonies, but because of lack of a selective advantage do not show phenotypically. The rough outgrowths possess the characteristics of R variants. The biochemical reactions of the R variants are identical to those of the parent S form. The mutational origin of the R variants from wild S types is demonstrated by a method involving the direct observation of rough clones. The mutation rate involved is presented for six of the strains. In continuous culture in broth both the S and the R types are stable. On agar the R variant is also stable.", }