Abstract
In the course of a study of F elimination by acriflavine, a new mating type, Fi (i=intermediate), was induced in F+ strains of E. coli K-12.
Two types of F+ were found; one having a tendency to spontaneously liberate F- cells, the other preserving its F factor firmly. It was found that acriflavine was especially effective in inducing Fi and F- from the former type.
Fi is distinguished from F+ and F- by the fact that it can mate with both F+ and F-, but is more fertile than F+ in crosses with a standard F+. Furthermore, Fi behaves as a recipient to F+, and as a donor to F- in recombination processes.
The phenotypic components of an Fi population are not uniform, but are composed of F+ -like, Fi and F- cells. When the population is transferred serially in broth, it has a tendency to become either F+-like or F-, especially the latter, with gradual changes of its components.
From these facts, it was assumed that there might be an unstable condition, the Fi state, between F+ and F-.
