Transferable colicinogenic factors as mobilizing agents for extrachromosomal streptomycin resistance

Abstract

Many strains with transferable colicinopenic factors were found to mobilize non-transferable but extrachromosomally located streptomycin resistance determinants in laboratory strains. I n 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 nesseesary t o check the donor strains for colicinogeny and t o destroy the colicines produced. Otherwise false negative results may be obtained.During the investigation of the so-called transfer factors (ANDERSON 1968) in antibiotic-susceptible wild type strains of Escherichi coli, it was found in this laboratory that, with only one exception, the susceptible transfer factor bearing (tj") strains of E . coli are colicinogenic and harbour a transferable col factor.Occurrence of the transfer factor property in some colicinogenic strains i. e. that function of a sex factor which provides transfer of non-transmissible but extrachromosomal resistance to antibiotics was also observed by LEWIS (1968). The principles of this mobilization were reviewed by MEYNELL et al. (1968).I n turn, we also observed that the strain E . coli K-260, bearing three colicinogenic factors, and some other strains with transferable colicinogenic factors (further designed as tf+col+) e . g. 63 R-82 and 62 G-1 were able to mobilize extrachromosomal but non-transferable streptomycin resistance (further designated as tj-S,,). It therefore seemed interesting to investigate, on a larger scale, the ability of the tf+col+ factors to mobilize and mediate the transfer of S-determinants which ot'herwise are not transferred to various recipient strains although localized extrachromosomally (LEWIS 1969. Therefore, 15 tf+col+ strains and 8 tf-col' strains i. e . strains with non-transmissible col factors were tested. Throughout this study, trypsine was used t o inactivate the colicines produced.

Pathogenomics of the Virulence Plasmids ofEscherichia coli

“…He also reported that a nontransmissible Col plasmid, when placed into the same cell as a conjugative plasmid, was transferred to recipient cells; such plasmids were deemed to be mobilizable, or capable of being moved from a donor to a recipient cell in the presence of another plasmid's conjugative apparatus. Fredericq also determined that these plasmids could be integrated into the host chromosome, and much subsequent work involved Hfr strains, which were shown in vitro to be capable of such integration (56)(57)(58)(59)96).…”

Colicinogeny and related phenomena.

“…Transfer is unaffected by the host recA mutation and can also be promoted by a traI mutant of F which cannot transfer F DNA although the cells harboring the plasmid form sex pili (4,478). The transfer of many small R factors is similarly promoted very efficiently by self-transmissible plasmids including group II Col factors (11,174,227,358,407). " From Harden (228) and personal communication.…”