COLICINE K VII. THE TRANS~V.R OF TYPE K COLICmOGENY

There can be but little doubt that the bactericidal activity of the colieine K which is elaborated by F~cherichia coli K235 resides in the protein portion of the bacterial somatic antigen (1). In its native state this component is firmly bound to a lipopolysaccharide and the two cannot be separated by the usual chemical or physical techniques. The question has arisen, however, as to what might happen were colicinogeny transferred from E. coli to another microorganism such as Shigella sonnei. Would the colicine again be produced as a protein-lipopolysaccharide complex or would it be released as an unconjugated protein? If the latter were true, our studies on the active site of the colicine molecule would be greatly simplified. On the other hand, were the new colicine to be released as a somatic antigen, one could now compare its properties with those of the somatic antigen of the noncolicinogenic parent strain used as the recipient. Such a study might reveal the changes which are brought about when a microorganism becomes colicinogenic. The investigation was therefore undertaken and evidence will be presented to show that type K colicinogeny can be transferred to Sh. sonnei. The new colicine is elaborated as a somatic antigen and, though its chemical and serological properties are strikingly different from those of colicine K, it will be seen that the two colicines do indeed possess certain properties in common.