Time-course of viral abundance (107 virus ml-1) and bacterial abundance (106 cell ml-1) in the four experiments during the incubation period. Values are given as mean ± standard deviation of triplicate incubations. Asterisks indicate sampling time point for which the VFA and VF treatments were not significantly different from the V treatment (ANOVA, P > 0.05, n = 9). Note that the panels have different scales. LA1, LA2, LB1, LB2: abbreviations as in Table 1.