Cell death induced by phage at high multiplicity of infection is not due to lysis inSalmonella typhimurium

Abstract

It has been reported [1] that high multiplicities of infection (MOI) with phage P22 produce a drastic decrease in the efficiency of transduction in Salmonella typhimurium. This phenomenon cannot be attributed to induction of lytic cycles by phage superinfection since it is known [2] that frequency of lysogeny is greater after infection at high MOIs than at low ones. An unexplored possibility to explain this phenomenon is that infection of S. typhimurium at high MOIs with phage P22 may induce an effect similar to lysis-from-without of Escherichia coli, where infection with phage T4 at high MOIs causes cellular death and lysis, but without production of phage. We present here the effect of infection, with temperate bacteriophage P22 and KB1 at high MOIs, on viability, absorbance and size distribution of cell cultures of S. typhimurium. To prevent lytic cycles which could be produced at low MOIs and distort the results, heavily UV-irradiated phage were used. The resuits show that infection of S. typhimurium at high MOIs with phage P22 or KB1 induces cellular filamentation and death but no lysis of the cells as happens in other phage-host cell systems. 2.1. Bacteria and bacteriophage