Isolation and properties of bacteriocin-tolerant mutants ofKlebsiella edwardsii var.edwardsii

Bacteriocin-resistant mutants ofKlebsiella edwardsii var.edwardsii were isolated, some of which, although still adsorbing the bacteriocin, were nevertheless insensitive (tolerant) to its effect.Selection was carried out with bacteriocins produced byKlebsiella pneumoniae (strains S6 and S8) andEnterobacter cloacae (strain DF 13). These bacteriocins are adsorbed by different receptor sites but have the same mode of action. Most of the isolated mutants (80–90%) could no longer adsorb any of the bacteriocins used. Therefore it is suggested that the different receptor sites on sensitive bacteria have some components in common. Seven different groups of tolerant mutants were isolated. The majority of these mutants are tolerant to the three bacteriocins used (Group I). In the other groups tolerance to one or two bacteriocins is accompanied by either sensitivity to, or resistance (non-adsorption) against, the other(s). The latter mutants must be considered as receptor mutants in which the specific stimulus sent from the bacteriocin receptor site through the cytoplasmic membrane to the intracellular target fails to initiate. Many tolerant mutants were extremely sensitive to desoxycholate and to ethylenediaminetetraacetate.The skillful technical assistance of Miss E. A. Spanjaerdt Speckman and Mr. E. Hoogendijk is gratefully acknowledged.