Transduction of resistance from a multiply antibiotic-resistant strain of sub-group II was studied using the typing phage 108. The effect of increasing doses of ultraviolet radiation on the transducing phage was used to indicate the chromosomal or plasmid nature of the genes. Tetracycline and chloramphenicol resistance behaved as plasmid genes and streptomycin resistance as a chromosomal marker. It was also possible to transduce penicillin resistance (Pc) due to penicillinase production ( ) using a low level of benzylpenicillin (0.03 μg ml) for recovery. Approximately 10 transductant colonies per phage input were obtained and ultraviolet kinetics indicated that Pc was plasmid carried. Pc transductants fell into two categories. In one group Pc was stable as in the donor strain and transductants had the same phage sensitivity as the recipient. In the other, Pc was unstable at 37C and the instability was enhanced by growth at approximately 43.5 C; these transductants also gained genes for restriction and modification of certain phages. Transductants that subsequently lost also lost the restriction and modification characters.


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