Aflatoxin B1 Induction of Lysogenic Bacteria

Abstract

A technique for biological verification of aflatoxin B1 was developed based on toxin-mediated induction of lysis in a lysogenic strain of Bacillus megateriun NNRL B-3695. Reduction of culture turbidity was determined at various concentrations of toxin. Incubation of 1.1 X 10-4 g (dry weight) of cells/ml of growth medium containing 25 ,ug of B, per ml at 37 C reduced initial turbidity 0.20 absorbance units in 4 hr. If the bacterial lysate of the lysogenic strain, after a 2-hr incubation with 25 ,ug of B1 per ml, was plated with a sensitive B. megaterium strain (NRRL B-3694), plaque-forming units increased approximately 150 times relative to the control. Comparable testing of the effects of aflatoxin on the nonlysogenic, sensitive strain demonstrated that 75 ,ug of B1 per ml neither induced lysis nor plaque-forming units. Although induction is not an exclusive property of aflatoxin B1, the differential response of the lysogenic and sensitive Bacillus strains to B1 offers a unique and rapid technique for biological verification of the toxin.