Effects of Mitomycin C and Thymidine Deprivation on Lysogenic and Sensitive Strains of Bacillus megaterium

Abstract

A triple auxotroph of Bacillus megaterium strain KM was lysogenized with a phage suspension from B. megaterium 899a. The lysogenic and phage-sensitive derivatives of KM were found to die at the same exponential rate during thymineless incubation, despite the fact that the lysogenic strain became induced. The lysogenic strain was also induced by mitomycin C, and died at an exponential rate which was approximately twice that of the sensitive strain. With both strains, the lethality of mitomycin C was the same in the presence and absence of thymidine; thymidine was required for maximal phage production. Mitomycin C preferentially inhibited deoxyribonucleic acid (DNA) synthesis of both strains for the first 60 min. The (DNA) synthetic ability of the lysogenic strain was subsequently restored, due to phage production. Since there was no evidence that sensitive strains of KM contained other inducible elements (prophage or probacteriocins), it is concluded that both thymineless death and mitomycin C death can occur via mechanisms not involving induction.

Properties of Thymineless Strains of Bacillus megaterium1

“…Previous studies with thymineless strains of Bacillus megaterium KM have shown that both lysogenic and phage-sensitive derivatives undergo similar rates of thymineless death, despite the fact that lysogenic strains are induced by thymine deprivation (5,6). Since there is no evidence that phage-sensitive strains of B. megaterium carry any inducible elements (prophage or probacteriocins), it was concluded that thymineless death occurs via mechanisms unrelated to phage induction (6).…”

Aflatoxin B1 Induction of Lysogenic Bacteria

“…Several reports have described procedures involving production of infective phage from lysogenic bacteria as a screening mechanism for compounds that cause tumors, mutations, or are tumoricidal (8,11,14,19,27). Mechanism studies of inducing substances have shown that they have in common the characteristic of inhibiting host cell deoxyribonucleic acid (DNA) metabolism (20)(21)26).…”