Colicin Js of Shigella sonnei: classification of type colicin "7".

Colicinotype 7 of Shigella sonnei, introduced by Abbott and Graham, is one of those most frequently found in epidemiological screenings. It is represented by the production of a single colicin (acidic protein of m. w. 46 kD) endowed with some striking features. It is unstable at pH 8.0 and at the temperature of 70 degrees C. Its inhibitive activity is specific for the species Shigella sonnei, most strains of which seem to be sensitive. It is the only colicin known so far inactive towards Escherichia coli, including the indicator strains of broad-spectrum sensitivity, such as K12 Row. It shows no cross-resistance with any other colicin type. Its adsorption on sensitive bacteria and inhibitive effect on them proceed extremely quickly. As indicated by indirect fluorimetry, its mode of action is extremely quickly. As indicated by indirect fluorimetry, its mode of action is probably different from those known for other colicins: it does not concern the plasma membrane of sensitive bacteria under aerobiosis, but it interferes with it under anaerobic conditions. These data show clearly that it is a unique colicin type. It is proposed to include it into the current system of classified colicins as "colicin Js".