Chromosomal Aberrations Associated with Mutations to Bacteriophage Resistance in Escherichia coli

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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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