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Escherichia coli strains that cause dysentery-like disease, parenteral infection, and infantile diarrhea form specific groups based on mobility of O and K antigens in immunoelectrophoresis. Members from each of these groups were assayed for gross nucleotide sequence relatedness. The method used was interspecific deoxyribonucleic acid (DNA) reassociation reactions carried out free in solution. Reassociated DNA was separated from unreacted DNA by passage through hydroxyapatite. DNA relatedness between these groups was approximately 80%. The groups containing those strains causing parenteral infection and those responsible for dysentery-like disease showed preferentially high intragroup DNA relatedness. The group containing strains responsible for infantile diarrhea did not show preferentially high intragroup DNA relatedness with the reference strain employed. These strains, however, did exhibit preferentially high DNA relatedness to a second reference strain.

The K88 antigen was carried by episomal transfer to D282, a nonmotile Escherichia coli strain without K antigen. D520, obtained by this episomal transfer, was used for the extraction of K88 antigen. It was shown by the agar gel precipitation technique that some K88 antigen was released from D520 into suspending aqueous medium. The amount of liberated material was increased by gentle heating (60 C) or treatment in a Waring Blendor. The antigen was obtained from the extracts in a purified form by making use of its insolubility between pH 3.5 and 5.5 and of its high sedimentation rate (S(0) (20,w) = 36.7S). The homogeneity of the material was demonstrated by agar gel precipitation with D520 antiserum, by analytical ultracentrifugation, and by moving-boundary electrophoresis. Chemical analysis revealed that K88 is a pure protein containing all the common amino acids with the exception of cysteine-cystine. Purified K88 selectively precipitated the K88 antibodies from D520 antiserum and was shown to be immunogenic in rabbits.

Hirota, Yukinori (Osaka University, Osaka, Japan), Yukinobu Nishimura, Frits Ørskov, and Ida Ørskov. Effect of drug-resistance factor R on the F properties of Escherichia coli. J. Bacteriol. 87:341-351. 1964.-Infection of Escherichia coli male cells (Hfr or F(+)) with resistance factor R results in the co-ordinate inhibition of several distinct functions of F factor: mating capacity to transfer chromosome by conjugation, production of f(+) antigen, and formation of receptors for the male-specific bacteriophages, f1 and ribonucleic acid phage. The i(-) mutant (R(100-1)) of R factor, which was isolated from wild-type R factor (R(100)), shows no inhibition of these F properties. Male R(+) (100-1) cells were autoagglutinable but the f(+) antigen was still present. When R-infected female cells had acquired the ability to form recombinants with an F(-) strain, they also had become autoagglutinable. The question of the presence of f(+) antigen in these strains was not solved. The cause of the autoagglutinability is not known, but it is not the result of loss of O antigen (rough autoagglutinability). Sensitivity to a phage tau, which can form plaques on female cells only, is not affected by the presence or absence of R factor. No difference in the pattern of segregation of recombinants was observed between the cross of Hfr R(-) x F(-) and that of Hfr R(+) x F(-). These results indicate that R factor controls a key mechanism in the synthesis of "F substances" formed on the cell surface by the F factor.

Ørskov, Ida (Statens Seruminstitut, Copenhagen, Denmark), and Frits Ørskov. Episome-carried surface antigen K88 of Escherichia coli. I. Transmission of the determinant of the K88 antigen and influence on the transfer of chromosomal markers. J. Bacteriol. 91:69-75. 1966.-The transmission of the determinant of the Escherichia coli K88 antigen in mixed cultures of E. coli strains is described. The K88 factor could not be transferred by filtrates, nor could responsible phages or colicines be detected. Acriflavine was shown to "cure" the bacteria for the K88 antigen. Generally, the strains having acquired the K88 antigen also acquired the ability to transfer chromosomal markers, but this ability was in some cases retained by segregants which had lost the K88 antigen. Introduction into an F(+) strain caused reduction of the recombination frequency and disappearance of the f(+) antigen. Not all wild-type strains with the K88 antigen are genetic donors of this antigen, at least not to a discernible degree. It was concluded that the K88 antigen determinant is carried by an episome.

Two nonfimbriate strains of Escherichia coli and their K88(+) counterparts, obtained by episomal transfer of this antigen, were studied with the electron microscope. Specimens were prepared with the spray drop method and were studied after shadow-casting. Under these conditions, the alteration in surface structure, due to the acquisition of K88 antigen, appeared as a fur of fine filaments, distinctly more flexible than fimbriae. Purified K88 antigen was also studied and found to have the same structure.