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Abstract
Studies of Escherichia coli performed using fresh or log phase cultures may not accurately represent the stationary phase characteristics of such cells in nature. The interaction between E. coli host cells and T4 bacteriophage is known to change in stationary phase. This study uses a standard plaque assay to observe the effects of E. coli ZK126 culture age on the ability of T4 bacteriophage to form infective centers. Cells grown for 2-9 days were subsequently infected with T4 bacteriophage at a multiplicity of 1 and plated with or without chloroform lysis at 60 and 120 minutes post infection. Cultures infected for 4, 5 and 9 days produced intact, unreleased phage progeny by 60 minutes. These were released in 4 and 5 day-old cultures by 120 minutes. Cultures incubated for longer and shorter periods did not produce or release high concentrations of assembled phage at either time point. When the supernatants of 2 day-old and 4 day-old cultures were swapped, it was found that cells that formerly showed little viral progeny production gained the ability to assemble, but not autonomously release, over 1,000 viral particles per infected E. coli cell. The 4 day-old cultures that formerly produced and released viral particles lost the ability to autonomously release viral progeny when swapped into 2 day-old cell supernatant. These results suggest that physiological changes in stationary phase E. coli ZK126 affect the efficacy of T4 bacteriophage infection and highlight the need for more stationary phase studies representing the actual events that occur in nature.