Effects of chloramine on Bacillus subtilis deoxyribonucleic acid

Abstract

The lesions induced in B. subtilis deoxyribonucleic acid (DNA) after treating bacterial cells (in vivo) and bacterial DNA (in vitro) with chloramine were studied biologically and physically. Single strand breaks and a few doublestrand scissions (at higher chloramine doses) accompanied loss of DNA transforming activity in both kinds of treatments. Chloramine was about three times more efficient in vitro than in vivo in inducing DNA single strand breaks. DNA was slowly chlorinated; the subsequent efficiency of producing DNA breaks was high. Chlorination of cells also reduced activity of endonucleases in cells; however, chlorinated DNA of both treatments was sensitized to cleavage by endonucleases. The procedure of extracting DNA from cells treated with chloramine induced further DNA degradation. Both treatments introduced a small fraction of alkali sensitive lesions in DNA. DNA chlorinated in vitro showed further reduction in transforming activity as well as further degradation after incubation at 50 C for 5 h whereas DNA extracted from chloramine treated cells did not show such a heat sensitivity.