Figure 3.
Maximal fitnesses (doublings/hr) seen in T7 and SP6 adapted to the hosts E. coli and Salmonella enterica. The normal host for T7 is E. coli, for SP6 is Salmonella enterica. There is a strong and similar effect of normal versus novel host for both phages, indicated by the parallel declines in fitness on the novel host. There is also a superiority of T7 over SP6 when host type is held constant. T7 and SP6 are both members of the Podoviridae, but they belong to different genera within the subfamily Autographivirinae.