抄録
Phage ε15 propagated on cells of Salmonella anatum (=A) shows efficiency of plating (EOP) of about 10-2 on cells of Salmonella butantan (=I-1), while ε15 propagated on cells of I-1 shows EOP of 10-4 on cells A. The some is true in phages produced by respective lysogenic derivatives. One cycle growth of phage on one strain results in production of phages with lower EOP on the other. This reciprocal shifting of EOP has proved experimentally to be due to host-controlled variation (HCV) and not to host range mutation by the following experiments.
Phages can be adsorbed well even onto cells with lower EOP and phage genetic material is injected into the cells, resulting in de novo synthesis of somatic antigen 15 on infected cells. Some of cells may revert to sensitive cells even after being injected with genetic materials of restricted phages.
When cells I-1 were mixedly infected with ε15 [A] and ε15vir [A], number of mixed yielders was far more than that calculated under the assumption that each of ε15 [A] and ε15vir [A] contains a host range mutant capable of attacking cells of I-1 at a proportion of 10-2 and 2×10-2, respectively.
On the other hand, it has been shown that EOP is partly dependent on physiological states of cells and also that multiple infection may lead to phage multiplication even in cells which do not allow phage growth when singly infected.
