Lysogeny and virulence in Bacillus anthracis cultures

Abstract

The purpose of this study was to determine if the virulence of two Bacillus anthracis cultures was directly associated with lysogeny. Two known virulent lysogenic cultures, designated AM1 and AM2, were selected for this study. Nonlysogenic derivatives of the lysogenic strains were produced by ultraviolet light irradiation of the parent strains for 250 seconds at a standard distance of 30 cm. Growth of colonies from cells that survived irradiation was inoculated into tryptose broth containing 10% rabbit antiphage serum; then streaked on tryptose agar. It was shown that ultraviolet irradiation alone would not produce nonlysogenic cultures. Nonlysogenic derivatives, designated AM1(-) and AM2(-), were plated with phage designated AM1p and AM2p, which originated from the parent strains AM1 and AM2, respectively. After 24 hours of incubation, confluent lysis occurred. Following an additional 24 hours of incubation, resistant colonies appeared with in the confluent plaques. Colonies were picked from these areas and substreaked several times before testing for lysogeny. Two "artificial" lysogenic cultures, designated AM1(+) and AM2(+) were used for the studies on virulence. ...