R (Transmissible Drug-resistance) Factors in Salmonella typhimurium: Pattern of Transduction by Phage P22 and Ultraviolet-protection Effect

Abstract

S U M M A R YR factors from Enterobacter strains isolated outside Japan were transferred to Salmonella typhimurium LT 2 and their resistance traits transduced by phage P 22. Of five$+ factors conferring resistance to tetracycline (Tc), streptomycin (Sm), sulphonamides (Su) and chloramphenicol (Cm), three, one of which conferred also resistance to kanamycin (Km), behaved like previously reported factors in that: Tc was transduced by itself but never with any other trait; all other traits were usually co-transduced; no transductants could transmit resistance by conjugation, even after infection with F'-13 lac. The other two $+ factors, which conferred also resistance to benzylpenicillin (Pn), behaved similarly, except that : Pn was transduced only at a low rate, and was never co-transduced with any other trait; and a few transductants when given F'-13 lac became able to transmit. Four $-factors, two of type Tc, Sm, Su, Pn and two of type Tc, Su, Pn differed in that : nearly all Tc transductants acquired also all the other traits; Pn was usually co-transduced with the other traits ; and some transductants could transmit by conjugation, even without F'-I 3 lac. The various transductant classes obtained by treatment with P 22 grown on LT 2 carrying both an$+ (Tc, Sm, Su, Cm, Km) and$-(Tc, Sm, Su, Pn) factor could be accounted for by transduction of fragments of either one or the other of these factors. The sorts of transductants produced by lysates of a strain possessing Tc, Sm, Su, Cm, Km determinants obtained by growing a strain carrying a n 3 + (Tc, Sm, Su, Cm) factor with one carrying an$+ (Km) factor suggested that the strain carried two $+ factors, not a recombinant factor. Both Ji-and $+ factors conferring resistance to benzylpenicillin conferred also resistance to cephalothin and cephaloridine and caused the constitutive production of a 1-lactamase, active on both benzylpenicillin and on cephalothin. All four-fi-and one of the five$+ factors resembled colI factors in that they protected strain LT 2 against the bactericidal effect of ultraviolet irradiation.

Properties of R Plasmids Determining Gentamicin Resistance by Acetylation in Pseudomonas aeruginosa

“…By spectrophotometric assay (4), the presence of gentamicin acetyltransferase in sonic extracts of Capetown no. 18 and Stone no. 130 was confirmed (11,39).…”

Plasmid Modification of Radiation and Chemical-mutagen Sensitivity in Pseudomonas aeruginosa

“…Certain plasmids such as some colicin factors (Howarth, 1965(Howarth, , 1966)~ several enteric R factors (Drabble & Stocker, 1968;Marsh & Smith, 1969;Siccardi, 1969; MacPhee 1972, 19-73 b) and particular Pseudomonas aeruginosa sex factors (Krishnapillai, I 975) confer protection against the lethal effects of ultraviolet radiation on their hosts while increasing the susceptibility of the host to the mutagenic effects of ultraviolet (u.v. ) light.…”

R Factor-mediated Resistance to Ultraviolet Light in Strains of Escherichia coli Deficient in Known Repair Functions

“…irradiation on wild-type bacteria (Howarth, 1965;Drabble & Stocker, 1968;Marsh & Smith, 1969). These include the fi-N group R factor R46, which has also been designated R-Brighton (Anderson & Datta, 1969, R1818 (Datta & Kontomichalou, 1965 and TP12o (Grindley, Grindley & Anderson, 1972).…”