The Nature of the Colicin K of Escherichia coli K235

When E. coli K235 is grown in the presence of mitomycin C it elaborates part of its colicin as a protein, which has been purified by gel filtration and electrofocusing to yield a product that is serologically homogeneous. The colicin K of E. coli K235 is chemically and serologically identical with that of Proteus mirabilis . Like the colicin of the latter, the E. coli bacteriocin occurs in multiple forms that exhibit slight differences in mobility upon electrophoresis in a polyacrylamide gel.