Chromosomal Aberrations Associated with Mutations to Bacteriophage Resistance in Escherichia coli

Abstract

Curtiss, Roy, III (University of Chicago, Chicago, Ill., and Oak Ridge National Laboratory, Oak Ridge, Tenn.). Chromosomal aberrations associated with mutations to bacteriophage resistance in Escherichia coli. J. Bacteriol. 89:28–40. 1965.—Ten types of mutants of Escherichia coli 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,λ, and /3,4,7,λ,pro⁻_1,2 mutants were unstable, changing to complete sensitivity to T₄. The results with strains having /3,4,7,λ,pro⁻_1,2 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,λ,pro⁻_1,2 mutation behaved genetically as a deletion. The /3,7,λ,pro⁻_1,2 and /3,4,7,λ,pro⁻_1,2 mutations caused positive interference, inhibition of genetic recombination in regions adjacent to them, and the formation of unstable partial diploid recombinants. One group of /3,4,7,λ mutations did not occur in the leu to try region of the bacterial genome. Other /3,4,7,λ 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,λ mutations at this locus were unable to conjugate; therefore, a complete genetic analysis of the effects of this /3,4,7,λ mutation could not be done.

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