[Origin of plague moderate phages of serotype 2].

Results of study of the negative colonies morphology, the structure of corpuscles, antigenic properties, specificity, and the action range permitted to refer the phages obtained from 18 E. coli strain, 1 plaque strain, and 1 pseudotoberculosis bacillus strain to the same group and to identify them with plague phages of serological type 2. Isolation of the same phage type from different bacterial species permits to regard them as "polyhostal" ones. E. coli should be considered as the main carrier of phages belonging to serological type 2. It is suggested that phages existing on microbes belonging to different species should be called "polyhostal".