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Behavior of three colicine factors and an R (drug-resistance) factor in Hfr crosses in Salmonella typhimurium
Published online by Cambridge University Press: 14 April 2009
Extract
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 sequence
The introduction into the Hfr of the colicine factors colI, colE1 and colE2 and the R factor R2 had 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 (colI 5–30%, colE1 30–80%, colE2 5–30%, R2 0–9%). Transfer of colE1 occurred before 20 min., that of colE2 and colI later 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 acquired colE2 and colI. Nearly all recombinants and F− cells which acquired colI or colE2 acquired both, and colE1 also. Most cells which acquired R2 acquired one or more colicine factors. These plasmid associations can be formally represented by transfer of plasmids, independently of the chromosome, in the sequence colE1—(colI, colE2)—R2. Phage P22 grown on the Hfr carrying the four plasmids transduced the tet-r trait of R2 at very low frequency, and the sul-r str-r characters, together, at low frequency. Some of each sort of drug-resistance transductant, but no transductants in respect of chromosomal characters, acquired colEl or colE2 by co-transduction.
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- Copyright © Cambridge University Press 1967
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