Bacteriophagy of Bacillus mycoides with Reference to Effect on Dissociation and Transmission by Spores.

Because of its unique colony form Bacillus mycoides has been a favorite species for the study of dissociation and life cycles. The mutually confirmatory reports of Nyberg (1929), Lewis (1932) and den Dooren de Jong (1933) have shown that this species is characterized by marked colonial polymorphism and that the sequence of events in dissociation is readily followed in cultures. So far as we are aware no complete study has been made as to the effect of bacteriophage on dissociation in B. mycoides. Since marked effects have been reported for other species it seemed that a detailed study of dissociation of B. mycoides in the presence of a bacteriophage should afford results of interest and value. The strains of B. mycoides used in a previous investigation of this species, (Lewis (1932)) have been employed in the present study. The bacteriophage was isolated from domestic sewage by a slight modification of the method described by Keller (1931). Difficulty was encountered in obtaining a high-titer bacteriophage for the original type strains but not for variants. Although numerous feeding and filtration experiments were carried out, the titer was never more than about 10-i for the original while a titer of 10-8 was readily obtained for the variants. Secondary growth occurred in all broth cultures with age. Plaques which developed in nutrient 1 per cent agar were rather large and corresponded roughly with the titer obtained in nutrient broth. When spread on the surface of inoculated agar plates the variant strains showed complete clearing, in which some secondary growth could 195