EPISOME-MEDIATED TRANSFER OF DRUG RESISTANCE IN ENTEROBACTERIACEAE VII. : Two Types of Naturally Occurring R Factors

AUTOR(ES)
RESUMO

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 T1 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 T7 as well. Phages λ and T1 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. CaCl2 exhibited antagonistic actions against the restrictions of phages λ and T1 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 T1 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.

ACESSO AO ARTIGO

Documentos Relacionados