Chromosomal Aberrations Associated with Mutations to Bacteriophage Resistance in Escherichia coli

Abstract

Ten types of mutants of Escherlchla coll K-12 resistant to bacteriophage T3 have been isolated, and several of these types have been studied genetically. Many of the /3,4,7,/3,4,7, lambda, and /3,4,7,lambda,pro1,2 mutants were unstable, changing to complete sensitivity to''T4. The results with strains having /3,4,7,lambda,pro1,2 mutations were compatible with the hypothesis that this mutation caused a single break in the circular chromosome which prevented the_normal association in the inheritance of the outside markers leu and lac . When sensitivity to T4 was regained, association in the inheritance of outside markers was restored, and the resulting /3,7, lambda, prof, 2 mutation behaved genetically as a deletion. The /3, 7, lambda, pro1,2 and /3,4,7,lambda,pro1,2 mutations caused positive interference, inhibition of genetic recombination in regions adjacent to them, and the formation of unstable partial diploid re-combinants. One group of /3,4,7, lambda mutations did not occur in the leu to try_region of the bacterial genome. Other /3,4,7,lambda mutations in F bacteria prevented the joint inheritance of the outside markers lac+ and gal+, presumably by breakage of the circular chromosome. Hfr and F+ strains with /3,4,7,lambda mutations at this locus were unable to conjugate; therefore, a complete genetic analysis of the effects of this /3,4,7, lambda mutation could not be done.