@article{mbs:/content/journal/micro/10.1099/00221287-24-3-355, author = "Li, Koibong and Barksdale, L. and Garmise, L.", title = "Phenotypic Alterations Associated with the Bacteriophage Carrier State of Shigella dysenteriae", journal= "Microbiology", year = "1961", volume = "24", number = "3", pages = "355-367", doi = "https://doi.org/10.1099/00221287-24-3-355", url = "https://www.microbiologyresearch.org/content/journal/micro/10.1099/00221287-24-3-355", publisher = "Microbiology Society", issn = "1465-2080", type = "Journal Article", abstract = "Summary: Shigelladysenteriae strain 136-R4 is lactose-negative, mannitol-negative (Lac−Mann−) and is sensitive to bacteriophage T7. Carrier clones of strain R4 (contaminated with T7) were found to maintain their association with phage T7 through as many as fifty consecutive single-colony isolations (from an ancestral colony which had survived lysis by phage T7). All carrier cultures (so-called pseudolysogenic strains) were found to be lactose-positive and mannitol-positive (Lac+ Mann+). Passage of Lac+ Mann+ bacteria through media containing antiserum directed against phage T7 resulted in a change back to Lac− Mann− and in the complete elimination of phage T7. Biochemical, genetic and immunochemical evidence indicates that the change from Lac− Mann− to Lac+ Mann+ is the result of a phage-controlled alteration in the phenotype of Shigelladysenteriae. This dysentery bacillus is cryptic with respect to the expression of Lac+ Mann+ and the crypticity is attributable to surface structures (which are probably not a part of the Y or permease system). Under appropriate conditions decryptification may be brought about by phage-associated endolysin. Similar phenomena were observed in carrier strains of certain other members of the Enterobacteriaceae.", }