Printed in Great Britain 265 Phage Growth Characteristics on Stationary Phase

The growth characteristics of ~3a bacteriophage on stationary phase Achromo-bacter strain 14 are described. Phage ~3 a growth on stationary phase cells is characterized by a long and variable latent period of 6 to 9 h and an increased burst size of 7Io p.f.u./cell as compared with I53 p.f.u./cell in exponential wild type cells. During the latent period the infected cells are very sensitive to changes in growth conditions and in particular, dilution. Pre-conditioning of the bacterial cells by allowing them to stand for 24 h after shaking for 3 days is an important aspect of the stationary phase phage growth system. Cells which have been allowed to stand retain the ability to be infected and to support phage growth for at least I6 days. Shaking cultures gradually lose the ability to support phage growth but the phage can persist in the host cell for to days until removal from shaking when the lytic cycle can proceed after allowing the cultures to stand