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Artificial Elimination of F factor in Bact[eria] coli K-12

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  • Ecology
  • Geography


Artificial eliminatfon of F factor in Bact. coli K-12, A few years ago, Lederberg and his co-workers (1952; 1953) fsund that in Bact. cgli K-12 there was a difference in sex-compstibility between the two mating cells, one having a transmissible agent, F, and the other lacking this agent. Hayes (1953h) demonstrated that these mating types were very stable heritable characters, but, the accidental disappearance of the F factor was f&d by Lederberd 6. al. (1952), and by Hayes (1953a). The study‘rep'orted here reveals that it is possible to obtain F' cells at will from F+ cells under certain environmental conditions. This phenomenon may be called "F eli:nination". The environmental factor responsible for F elimination is the cobalt or nicks1 concentration in the medium ( Co(N4 1 t CoCl 32 2' etc.; Ni(N33)2, NiSJ4, etc.). The first method of artificial eliminatin of F factor is called the “&v&44-” trBTV method. A culture of F' cells was inoculated into yeptone medium ( peptone, log. and glucose, 2g. in 1 liter distilled wate:'.j , and incubated overnight at 37'C. Bfter 24hrs., c>,15ml. of &4X. cobalt sAution was added to 3 ml. of the culture ( the final concentration was 20mX.) which was Incubated for 24 hrs. m$eI' This treated culture was then spread on nutrient ager containing 40mM. of sodium citrate, which was used for detoxification of cobalt, and single colonies grown on the medium were isolated at random. By this procedure, it was found that many colonies wsre converted Into Fr For example, in the mutant K-12 strain 58-161 and the derived strains from 58-161, 10-30 ; of the colonies were converted into Fr However, all of the F- were sensitive to cobalt. 'i'he frequency of conversion varies according to the strain of Bact. coli K-12 used. The second method is called "resistant isolatiorP, in which cobalt- 2 medium containing cobalt in increasing concentrations. A slow and smooth increie of re

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