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 T 3 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 T 4 . 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 T 4 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.