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Abstract:
Single cells of Escherichia coli K12, infected with the male-specific phages fd (DNA phage) or fr (RNA phage), may release up to several hundred particles of progeny phage per division cycle while the active cells continue to divide. The fd-infected or fr-infected state, for their indefinite maintenance, require reinfection and tend to be lost if phage readsorption is prevented by extremely diluting the growing bacteria. Death of fd-infected cells is infrequent (at 36°C), as judged from microscopic control and the high rate of bacterial growth observed in mass infection. Infection with fr phage leads to visible clearing of the infected cultures at 37° but is nonlethal if the infected cells are grown at 31°. Established infection of mass cultures with either fd or fr is reflected by a proportional increase of phage and bacterial counts, a phenomenon whose significance is discussed.
