GENETICS OF TWO DIFFERENT MECHANISMS 

 OF RESISTANCE TO COLICINS : RESISTANCE 



BY LOSS OF SPECIFIC RECEPTORS AND 

 IMMUNITY BY TRANSFER OF COLICINOGENIC 



FACTORS 



Pierre Fredericq 



Department of Microbiology and Hygiene^ University of Liige 



Introducing colicins and colicinogenic factors 



Many strains of Escherichia coli or related strains produce 

 antibiotic substances known as colicins (Fredericq, 1946a). 

 These colicins are highly specific antibiotic agents which kill 

 susceptible bacteria belonging to the same family, mostly 

 other Esch. coli or Shigella sonnei strains (Fredericq and 

 Levine, 1947; Fredericq, 1948^/; Halbert, 1948; Mondolfo, 

 1948; Chabbert, 1950; Grosso, 1950; Blackford, Parr and 

 Bobbins, 1951; Levine and Tanimoto, 1954). 



Colicins produced by various strains may differ by many 

 characteristics : extent and specificity of their activity spectra, 

 specificity of resistant mutants, morphology of inhibition 

 zones in agar, diffusibility, thermoresistance, susceptibility 

 to proteolytic enzymes (Fredericq, 1948^^; Chabbert, 1950), 

 electrophoretic motility (Ludford and Lederer, 1953) and 

 antigenic properties (Bordet, 1947; Goebel, Barry and 

 Shedlovsky, 1956; Hamon, 1956a). 



Despite their diversity, all colicins studied give the general 

 reactions of polypeptides or proteins (Heatley and Florey, 

 1946; Halbert and Magnuson, 1948; Depoux and Chabbert, 

 1953; Gardner, 1950). Cohcin K, which was recently purified 

 by Goebel and co-workers (1955), appears to be a macro- 

 molecular substance, consisting of carbohydrate, protein and 

 lipid, and containing 6-5 per cent nitrogen and 1 -6 per cent 



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