Abstract
When niacin requiring Escherichia coli (λ) was superinfected with λ phage during development of niacin deficiency, conversion of the injected molecule to covalently closed or nicked circles decreased in accordance with the reduction of cellular NAD (nicotinamide adenine dinucleotide) content. This finding suggested that host DNA ligase, which required NAD and induced the conversion, was not functional. In niacin deficient E. coli, vegetative growth of λoccurred, indicating that there were enough materials within the deficient cells to support multiplication of the phage. However, neither induction of prophage λ nor growth of superinfecting λCI after treatment with mitomycin C was observed in E. coli (λ). This indicated that the immunity substance was active in niacin-deficient E. coli (λ) even after treatment with mitomycin C.
