Watanabe, Tsutomu (Keio University, Tokyo, Japan), Hiroshi Nishida, Chizuko Ogata, Toshihiko Arai, and Sachiko Sato. Episome-mediated transfer of drug resistance in Enterobacteriaceae. VII. Two types of naturally occurring R factors. J. Bacteriol. 88:716-726. 1964.-Naturally occurring R factors are classified into two types, fi(+) and fi(-), depending on their fi characters. The term fi is an abbreviation of fertility inhibition and fi(-) and fi(-) mean, respectively, the presence and absence of suppression of the functions of the sex factor F of Escherichia coli K-12. It was found that fi(-) R factors reduce the efficiency of plating of phages lambda and T(1) in K-12; fi(+) R factors did not have this inhibitory action. One of the fi(-) R factors reduced the efficiency of plating of phage T(7) as well. Phages lambda and T(1) underwent host-induced modifications in the host carrying some fi(-) R factors. At least two types of fi(-) R factors were recognized by the types of their restriction and host-induced modification of these phages. CaCl(2) exhibited antagonistic actions against the restrictions of phages lambda and T(1) by fi(-) R factors. Transduction of the ability to ferment galactose with HFT lysates of lambda was reduced by fi(-) R factors. Ultraviolet induction of lambda was not affected by any R factors. Furthermore, adsorption of phages lambda and T(1) was not altered by the presence of any R factors. From these results, we concluded that the suppression of progeny formation of these phages by fi(-) R factors is due to some step(s) after adsorption of the phages to the bacteria. Superinfection immunity and mutual exclusion were found between two different fi(+) R factors but not between fi(+) and fi(-) R factors. The two different fi(-) R factors were frequently genetically recombined. but fi(+) and fi(-) R factors were not genetically recombined, as indicated by findings of independent transfer of these R factors by conjugation and by transduction from the donors having these two R factors. It was assumed from these findings that fi(+) and fi(-) R factors are considerably different episomes having different resistance-transfer factors.

Acridines↗

PubMed1964

EPISOME-MEDIATED TRANSFER OF DRUG RESISTANCE IN ENTEROBACTERIACEAE. 8. SIX-DRUG-RESISTANCE R FACTOR.

Watanabe, Tsutomu (Keio University School of Medicine, Tokyo, Japan), Chizuko Ogata, and Sachiko Sato. Episome-mediated transfer of drug resistance in Enterobacteriaceae. VIII. Six-drug-resistance R factor. J. Bacteriol. 88:922-928. 1964.-The multiple-drug-resistant Escherichia coli strain isolated by Lebek in 1963 was found to transfer resistance to sulfonamide, streptomycin, chloramphenicol, tetracycline, kanamycin, and neomycin together by conjugation, as well as by transduction with phage P1kc, suggesting that these drug-resistance markers are carried by a single R factor (R(6)). The results of transductional and spontaneous segregations of the drug-resistance markers of R(6) have shown that R(6) has independent genetic determinants for sulfonamide, streptomycin, chloramphenicol, tetracycline, and kanamycin-neomycin resistance. Resistance to kanamycin and neomycin is probably controlled by a single gene, because no segregation was observed between these two. The resistance transfer factor of R(6) was found to be of the fi(+) type.

Anti-Bacterial Agents↗

PubMed1964