Abstract
The O antigen of E. coli K235 can be separated chromatographically into a series of fractions having different affinities for DEAE cellulose. These fractions are very closely related chemically. Though their avidity for homologous antibody exhibits variation, they are serologically homogeneous, save for one. All of the fractions have nearly identical colicine K activity. It has not been possible to separate the bactericidal activity from the Oantigen of E. coli K235.