CHARACTERS OF NON-FILAMENTOUS DERIVATIVES OF ESCHERICHIA COLI STRAIN B_s-1 COMPARED WITH RELATED STRAINS OF E. COLI K12 AND B

Abstract

Non-filamentous (Fil^-) derivatives were isolated from E. coli strain B_s-1 and its lysogenized strain B_s-1(80). These Fil^- strains were 70 times more UV resistant, 1.5 times more X-ray resistant and had lower growth rate than B_s-1 and B_s-1(80). Transfer of episome F'13 resulted in complete (or partial) reversion of their characters to those of strain B_s-1 (or B_s-1(80)). Entry of episome F'13 altered the Fil^- UV^r phenotype of gene lon⁺ in wild-type K12 strains to Fil⁺ but UV^r phenotype, and the Fil⁺ UV^s phenotype of gene lon in filamentous K12 mutants to Fil⁺ but UV^r phenotype, whereas it did not affect the Fil⁺ UV^s phenotype of gene uvs in strains B and B_s-1. The following conclusions are reached. 1) Fil⁺ character is not necessarily correlated with UV^s character. 2) Gene uvs is not identical (but probably allelic) to lon and dominant to lon⁺. 3) Gene lon⁺ is dominant to lon for radiation resistance but not so for Fil^- character. 4) Fil^-, UV^r and slow-growing characters are induced in strain B_s-1 through genetic suppression of function of uvs by single or multiple suppressor genes. 5) Conclusion 4) may be related to the mystery why the extremely UV^s strain B_s-1 was discovered by Hill (1958) in surviving colonies of heavily UV irradiated culture of strain B. 6) The newly found suppressor gene in Fil^- derivatives of strain B_s-1 seems to have ability to give higher UV resistance than similar suppressor gene in B/r type strains.