EPISOME-MEDIATED TRANSFER OF DRUG RESISTANCE IN ENTEROBACTERIACEAE VII

Abstract

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 λ 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 λ 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 λ and T 1 by fi − R factors. Transduction of the ability to ferment galactose with HFT lysates of λ was reduced by fi − R factors. Ultraviolet induction of λ was not affected by any R factors. Furthermore, adsorption of phages λ 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.