Effects of mixed-function oxidase and aflatoxin B1 on lysogenic and indicator strains of Bacillus subtilis

The present study was conducted to determine the effects of metabolized aflatoxin B1 (via a mammalian liver mixed-function oxidase system) and native aflatoxin B1 upon induction of bacteriophage in Bacillus subtilis and growth of B. subtilis. A lysogenic strain of B. subtilis (BDS-1, phi 105) and an indicator strain of this species (DBS-1) were utilized in the present experiment. Lysogenic cultures were incubated for various lengths of time in the presence of either native or metabolized toxin, and plaque-forming units were determined. Identical experiments were conducted with the indicator strain and colony-forming units were determined. At a native toxin concentration of 25 micrograms/ml of medium, the maximum number of plaque-forming units was induced in lysogenic cells. However, when cells were incubated in the presence of aflatoxin B1 and mixed-function oxidase, neither plaque-forming units nor colony-forming units could be detected from lysogenic or indicator cells, respectively. This organism is apparently much more susceptible to inhibition of cellular replication than to lysis via bacteriophage induction. Thus, from the present study and from previously reported research, differences in susceptibility to native and metabolized aflatoxin B1 exist among species of Bacillus.