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Appl Environ Microbiol. 1970 November; 20(5): 782-785
Copyright © 1970 American Society for Microbiology. All Rights Reserved.

Aflatoxin B₁ Induction of Lysogenic Bacteria

Northern Regional Research Laboratory, U.S. Department of Agriculture, Peoria, Illinois 61604

ABSTRACT

A technique for biological verification of aflatoxin B₁ was developed based on toxin-mediated induction of lysis in a lysogenic strain of Bacillus megaterium 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 µg of B₁ 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 µg 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 µg 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.