The influence of host growth temperature, phase and media, together with the effect of infection temperature on bacteriophage PhiS1 infection of Pseudomonas fluorescens were examined. The rates of cell lysis and phage release were determined and showed that the efficacy of phage infection was optimal with host cells grown and infected at 26 degrees C. The host physiological state also affected these rates. Infection was dependent on the presence of cell wall proteins with molecular weights of 17.5+/-1 and 99+/-5 kDa.