The Metabolic Activities of Escherichia coli during the Establishment of Lysogeny

Abstract

SUMMARY: Escherichia coti strain K112 was infected with h phage (multiplicity of input 20 particles/cell) in O-O~M-M~SO,, and 91 yo infected cells gave the lysogenic response. When the infected cells were transferred to a complete amino acid medium containing l4C-~~-pheny1alanine and a non-utilizable inducer for /3-galactosidaseY the net synthesis of protein and nucleic acids did not begin until after 100-120 min. During this period there was no induced synthesis of P-galactosidase (though the enzyme was readily developed in uninfected cells) and there was no increase in turbidity of the culture or in viable cell count. The synthesis of protein and nucleic acids began in uninfected cells immediately they were placed in the complete medium, turbidity increased from the start and the viable count after 30 min. This suggested that during lysogenization the infecting phage temporarily halts most if not all of the synthetic activities of the cell and thus forms an environment in which the phage genome can become attached to the bacterial chromosome and establish the prophage state.The biochemical changes which occur after infection in a cell which is to become lysogenic have not been studied before in any detail. Whilst much attention has been given to the biochemical effects of infection of Escherichia coli by the T phages, only a few experiments (cf. Lwoff, 1954-5) have been concerned with the effect of temperate phage on the metabolism of the host cell. The purpose of the present work was to attempt to study what determines the choice between the lytic and the lysogenic response, since the factors controlling this decision are not understood. At least in some bacteria, lysogeny is favoured by a high multiplicity of infection (Boyd, 1951), and after infection, changes in the environment, e.g. changes in temperature (Bertani & Nice, 1954), or the presence of substances which prevent protein synthesis (Lwoff, Kaplan & Ritz, 1954;Christensen, 1957) can alter the type of response. Conditions have been established for infecting virtually all the cells of a suspension of E. coti with h phage, and thus obtaining a population in which more than 90 yo of the infected cells give the lysogenic response. Some of the biochemical activities of these cells were examined and are reported here. A summary of these results has been given previously (Fry & Gros, 1958). METHODSThe organism, Escherichia coli strain K l l 2 , the preparation of washed cell suspensions and stock suspension of phage lambda the composition of nutrient broth, the detection of response of infected cells and the determination of viable counts have been described previously (Fry, 1959).

The Infection of Escherichia coli with Lambda (22) Phage and the Establishment of Lysogeny

“…after infection. Though this time differs from that obtained in the mating experiment, it is in keeping with the observation (Fry & Gros, 1959) that bacteria in which lysogeny is being established do not grow and metabolize normally until 60-80 min. after infection.…”

“…Bacteria which are becoming lysogenic for h phage show a delay in cell division and disturbance of their metabolism (Fry & Gros, 1959). These findings could be explained on the basis that they reflect the time required for the prophage to become established or, that the prophage may be established soon after infection but the events connected with this process cause a profound upset in the metabolism of the host bacterium which takes an appreciable time to recover.…”

“…After infection with a temperate phage, the metabolism of bacteria which are to become lysogenic seems to be profoundly disturbed and when the bacteria are placed in a growth medium one reflexion of this disturbance is a long delay before division occurs (Lieb, 1953;Fry & Gros, 1959). Moreover some bacteria may divide more than once before the prophage is fully established when no more non-lysogenic progeny segregate (Luria, Fraser, Adams & Burrows, 1958).…”

ISOLATION AND PRELIMINARY CHARACTERISTICS OF THREE BACTERIOPHAGES ASSOCIATED WITH A LYSOGENIC STRAIN OF PSEUDOMONAS AERUGINOSA ,

“…In particular, it would be well to know whether the lysis inhibition observed is a consequence of superinfection by phage 7v particles, as has been shown to be the case for the lysis inhibition of phage T2 (Doermann, 1948), or whether it is a result of superinfection by temperate phages such as phage 7m which are present in Ps-7 cultures in relatively high concentrations. In view of the demonstration (Fry and Gros, 1959) that significant metabolic disturbances in bacterial cells are brought about during the establishment of lysogeny, it could be postulated that the abortive infection as well as the lysis inhibition observed in this system is a consequence of super-PHAGES ASSOCIATED WITH P. AERUGINOSA infection by temperate phages. Unfortunately, the results obtained by the infection of a multilysogenic host system cannot be entirely attributed to the interaction of a single virus with the host cell; our attempts to isolate nonlysogenic, sensitive strains of P. aeruginosa have not been successful (Feary et al, 1963b).…”