Transferable colicinogenic factors as mobilizing agents for extrachromosomal streptomycin resistance.

Abstract

Many strains with transferable colicinogenic factors were found to mobilize non-transferable but extrachromosomally located streptomycin resistance determinants in laboratory strains. In turn, with only one exception, all strains which were found in triparental crosses to mobilize the transfer of the S-determinants harboured a transferable col factor. These findings may show the ecological importance of transferable colicinogenic strains which occur frequently among wild type strains of E. coli in the origin and spreading of resistance transfer factors under natural conditions. When studying transfer factors and transferable resistance, it is nessessary to check the donor strains for colicinogeny and to destroy the colicines produced. Otherwise false negative results may be obtained.