Interaction of aflatoxin B1 with bacterial DNA: possible relationship to bacteriophage induction in lysogenic Bacillus megaterium.

Studies were conducted to determine possible interactions between aflatoxin B1 and deoxyribonucleic acid (DNA) and induction of bacteriophage formation in lysogenic Bacillus megaterium NRRL-B-3695. At pH 7.4, the spectrophotometric characteristics of B1 with various concentrations of calf thymus DNA were altered with both a hypochromic shift and a shift of the wavelength for maximum absorbance of the toxin. Aflatoxin B1 apparently interacted with DNA as indicated by spectrophotometric analysis and ultrafiltration studies. Under alkaline conditions (pH 10.0), spectrophotometric characteristics of this interaction were altered from those observed at pH 7.4. Toxin incubated at pH 7.4 could induce bacteriophage formation but failed to do so at pH 10. Preincubation of toxin with calf thymus DNA did not block subsequent induction. It is proposed that a bacterial DNA-toxin interaction, involving an alkaline-labile bond of aflatoxin B1, is necessary to cause induction of bacteriophage formation in lysogenic B. megaterium.