Characterization of Escherichia coli mutants tolerant to bacteriocin JF246: two new classes of tolerant mutants.

Several hundred independent bacteriocin-tolerant mutants have been isolated without mutagenesis from three strains of Escherichia coli. On the basis of patterns of sensitivity to eight different colicins, over 85% of these mutants could be grouped into four classes. Two classes of mutants, class A and class B, are equivalent to tolA and tolB type mutants. We found tolA and tolB mutants were sensitive to the antibiotic bacitracin. The other two classes of bacteriocin-tolerant mutants, class F and class G, are distinguished from other types of colicin-tolerant mutants on the basis of sensitivity to colicins, dyes, detergents, antibiotics, and chelating agents. The mutation in class F and class G mutants is located between 21 to 23 min on the E. coli chromosome. We propose to designate the loci of these mutations as tolF and tolG, respectively.