One-step growth curve, latent period and burst size

The adsorption assay was carried out according to Rahman et al. [28] with minor modifications. The log phase cultures of host strains were infected with phage suspensions at optimal multiplicity of infection (MOI) and incubated at 37 °C. At 0, 3, 6, 9, 12, 15, and 18 min of incubation, aliquots were taken (100 µl), mixed with LB medium (900 µl), and immediately filtered through a 0.22 µm pore size syringe filter. The titer of unadsorbed phage particles was determined by the double-agar layer method. The experiment was repeated three times for each phage.

To determine the latent period and phage burst size, a one-step growth curve was performed according to Yu et al. [29]. Phage suspensions were mixed with exponential growth phase cultures of host bacteria at optimal MOI. Samples were taken at 10 min intervals over a period of 80 min and phage titer was determined via the double-agar layer method. Latent time was measured as the interval between phage adsorption and the liberation of phage particles. Burst size was calculated as the ratio of the phage titer at the plateau phase to the initial count of infected bacterial cells/initial phage titer. Each experiment was performed in triplicate.