Genetics of host-controlled restriction and modification of deoxyribonucleic acid in Escherichia coli.

Lederberg, Seymour (Brown University, Providence, R.I.). Genetics of host-controlled restriction and modification of deoxyribonucleic acid in Escherichia coli. J. Bacteriol. 91:1029-1036. 1966.-The locus for the host specific restriction and modification of deoxyribonucleic acid in Escherichia coli has been mapped by matings between mutants for these characters in strains K-12, C600, and B. Linkage analysis and kinetics of marker transfer indicate that a single or closely linked multiple chromosomal site located about 4 min counterclockwise to leucine is responsible for these activities. Secondary factors which affect the quantitative level of restriction also were detected. Wild-type recombinants were isolated in crosses between rm(-) (restriction or modification, or both) mutants. The expression in zygotes of the restrictionless character of a rm(-) donor is masked by a separate, physiological impairment of restriction, which results from mating and is independent of the modification state of the donor. The relevance of the restriction character to mating incompatibilities in these and other bacterial strains is considered.