GENETIC VARIATION IN THE SEX FACTOR OF ESCHERICHIA COLI

Publisher Website
Google Scholar
Abstract
It has been shown that recombination occurs between attached sex factor (F) and chromosome in Hfr cells of Escherichia coli. Reciprocal exchange is evidenced by the changed properties of both partners: the sex factor acquires a high and specific affinity for the chromosomal site at which it had been attached, while returning to the autonomous state; the chromosome acquires an affinity at that site for either wild-type or recombinant sex factor. The recombinant sex factor is recognized by the fact that it is transmissible to F cells as an extra-chromosomal particle that convert the recipient cells to donors capable of transferring their chromosome with a specific orientation and with a relatively high frequence. The clone derived from the cell in which the recombination took place can be converted to F by treatment with acridine orange. On introduction of the wild-type F particle of strain K-12, these cells become high-frequency donors, unlike ordinary F cells, which are convertible by wild-type F only to low-frequency donors. This property reflects the presence of the sfa ("sex factor affinity") locus on the chromosome. A terminology is proposed for dealing with genetically varying sex factors, recombinant loci, and strains of bacteria carrying either or both.