Absence of competition between salmonella phage P22 and coliphage P1 for adsorption sites on a Salmonella typhosa - Escherichia coli hybrid strain.

Salmonella typhimurium mutants sensitive to coliphage P1 are resistant to salmonella phage P22 and lose their P1-sensitivity upon reversion to P22-sensitivity. A tryptophan-requiring Salmonella typhosa - Escherichia coli hybrid, which has the unique ability to serve as recipient in transduction mediated by both P22 and P1, was sued to determine if P22 and P1 adsorb at the same or overlapping sites: (i) The adsorption of each of P1 and P22 is similar when added individually or together to the hybrid at a saturating multiplicity of infection (moi). (ii) P1 grown on trp+ E. coli yields the maximum frequency of Trp+ abortive transductions at an moi of 6 with the trp hybrid recipient; the presence of increasing numbers of P22 grown on trp S. typhimurium does not decrease the number of Trp+ transduction from P1. (iii) A mixture of P1 (grown on trp+ E. coli) and P22 (grown on trp+ S. typhimurium) yields more abortive transductions than does P1 alone. Thus phages P1 and P22 adsorb to the hybrid cells on different sites.