Behavior of three colicine factors and an R (drug-resistance) factor in Hfr crosses inSalmonella typhimurium

Abstract

An LT2 Hfr strain,his metC gal, was crossed to a multiply marked LT2 F−line. Analysis of recombinant yields, segregation of unselected markers and interrupted matings indicated injection of the Hfr chromosome in the sequenceThe introduction into the Hfr of the colicine factorscolI, colE1andcolE2and the R factorR2had little or no effect on its fertility. All four factors were transmitted at low frequency to the F−population, and to recombinants at higher frequencies (colI5–30%,colE130–80%,colE25–30%,R20–9%). Transfer ofcolE1occurred before 20 min., that ofcolE2andcolIlater than 100 min. Segregation data did not reveal close linkage of any factor to any chromosomal locus, but recombinants with a long stretch of donor chromosome were more likely than others to have acquiredcolE2andcolI. Nearly all recombinants andF−cells which acquiredcolIorcolE2acquired both, andcolE1also. Most cells which acquiredR2acquired one or more colicine factors. These plasmid associations can be formally represented by transfer of plasmids, independently of the chromosome, in the sequencecolE1—(colI, colE2)—R2. Phage P22 grown on the Hfr carrying the four plasmids transduced thetet-rtrait ofR2at very low frequency, and thesul-r str-rcharacters, together, at low frequency. Some of each sort of drug-resistance transductant, but no transductants in respect of chromosomal characters, acquiredcolEl or colE2by co-transduction.

The pattern of evolutionary change in bacteria

“…One of these molecules carries the genes responsible for the transferability whilst the other carries the drug resistance determinants. What seems to be a similar phenomenon was reported by Dubnau and Stocker (1967). They introduced R factors and col factors independently into a strain of Salmonella typhimurium.…”

Co-Transduction of Plasmids Mediating Resistance to Tetracycline and Chloramphenicol in Staphylococcus aureus

“…The co-transduction of a different set of independent plasmids, a Col plasmid and an R factor, has also been reported (8).…”

Transmission of lac by the Sex Factor E in Erwinia Strains from Human Clinical Sources

“…It is now generally accepted that plasmid transmission is more frequent than previously thought among related bacteria sharing a common habitat (7,34,37). In addition, recombination between plasmids is known to occur under laboratory conditions (15,19,25,32,40,49) and possibly in nature (7,14). That plasmid inheritance might play a significant role in animal pathogenicity is indicated by the transmissible nature of ent (the determinant of enterotoxin production) and hly (the determinant of hemolysin production) among animal isolates of E. coli (38,41,42).…”