Inhibition of Enzyme Formation Following Infection of Escherichia coli with phage T2r+

The induction of L-arabinose isomerase in Salmonella typhimurium (LT2) is repressed on infection with clear plaque forming mutants (C1 and C2) of the temperate phage P22 (C+). However, after infection with C+ leading to lysogeny, there is a temporary repression. During this period, messenger ribonucleic acid (RNA) for L-arabinose isomerase accumulates. DNA-RNA hybridization data suggest that there is transcription of host DNA during the period of repression. Interference at the level of translation might be responsible for the cessation of induced enzyme synthesis.

supporting

confidence: 88%

Induction and Repression of l -Arabinose Isomerase in Bacteriophage-Infected Salmonella typhimurium

Chakravorty

1970

“…There is an abrupt block in the induction of certain host enzymes when E. coli is infected by bacteriophage T2 (12,24,31), T6 (6, 12), or T4 (this paper); there is also an abrupt block in the synthesis of constitutive 3-galactosidase after T6 infection (13). Thus, it seems likely that synthesis of many, if not all, host proteins terminate soon after infection by the T-even phages.…”

Section: Discussionmentioning

confidence: 79%

Inhibition of Host Protein Synthesis During Infection of Escherichia coli by Bacteriophage T4 I. Continued Synthesis of Host Ribonucleic Acid

Kennell

1968

The ribonucleic acid (RNA) synthesized at specified intervals during infection of Escherichia coli K-12 by bacteriophage T4 was hybridized to denatured E. coli or T4 deoxyribonucleic acids (DNA). The reactions were performed under conditions that maximized the yield and at RNA/DNA inputs such that excess DNA sites were available for all RNA species. Most of the RNA synthesized at any time during the first 3 min of infection was host-specific. The fraction declined rapidly as infection progressed; host RNA represented about half that made between 3 and 4 min. It is unlikely that this represented RNA synthesized by bacteria that had escaped infection, as judged by the kinetics of adsorption and killing as well as by the rapid inhibition of 3-galactosidase induction after infection. The nature of the host RNA was also examined. Part of the RNA synthesized during infection of cells rendered sensitive to actinomycin was stable in the presence of this inhibitor. This RNA was essentially all host-specific and it sedimented as ribosomal and transfer RNA; most of the ribosomal RNA was incorporated into 30S and 50S ribosomes. Hybridization analyses suggested that unstable E. coli messenger RNA was also synthesized for several minutes after infection; the proportion of unstable to stable host RNA synthesized appeared to be similar in infected and uninfected cells. Thus, it is concluded that significant amounts of E. coli RNA are synthesized during the first minutes of T4 infection. Host messenger RNA initiated after infection may not be translated into enzymes; alternatively, it is conceivable that continued bacterial messenger RNA synthesis only reflects the completion of transcription of operons whose reading was initiated prior to infection.

“…The ghosts were titered by a modification of the method of Duckworth and Bessman (9). Several 10-ml cultures of E. coli B (2 to 4 X 108 cells/ml) in TGA medium, nutrient broth, or in TY broth were placed in 125-ml Erlenmeyer flasks and supplemented with 20 pg of L-tryptophan per ml. Known volumes of ghost preparation were added to the cultures and the mixtures were allowed to stand at room temperature for 2 min.…”

Section: Methodsmentioning

confidence: 99%

Effect of Bacteriophage Ghost Infection on Protein Synthesis in Escherichia coli

Fukuma

Kaji

1972

The rate of protein synthesis by Escherichia coli markedly decreased within 1 min after phage T4 infection, whereas a complete cessation of protein synthesis was observed within at least 25 sec after T4 ghost infection. The cellular level of amino acids and aminoacyl-transfer ribonucleic acid (tRNA) did not change drastically upon infection with ghosts, indicating that the inhibition of protein synthesis took place at a step(s) beyond aminoacyl-tRNA formation. The host messenger RNA remained intact and still bound to ribosomes shortly after ghost infection. Kinetic studies of the effect of ghosts on host protein synthesis revealed that nascent peptide chains on ribosomes were not released upon ghost infection. Casamino Acids to a final concentration of 0.2%c. TY broth contained 10 g of tryptone, 5 g of yeast extract, and 10 g of NaCl per liter. Growth and infection of bacteria. Cells of E. coli B were grown at 37 C in an Eberbach reciprocal shaker. Growth was measured in a Klett colorimeter, and the Klett reading had been calibrated to the number of colony formers in the culture media. The mass doubling times were 50, 50, and 30 min, in TG medium, TGA medium, and TY broth, respectively. Cells were grown to a densitv of I to 5 X 108 cells/ml and were 713