Lysis of Bacterial Spores with Hydrogen Peroxide

Summary Spores of Bacillus cereus were made sensitive to lysis with H 2 O 2 by treatment with reagents which break disulphide bonds (e.g. thioglycollic acid), by incubation with reagents which break hydrogen bonds (e.g. urea and lithium bromide) or by incubation at high temperatures. However, treated spores lost viability in the presence of H 2 O 2 at the same rate as did untreated spores. Lysis was optimal at high pH values and in the presence of metal ions, e.g. Cu 2+ , suggesting that lysis was caused by free radicals formed by metal catalysed decomposition of the peroxide. Isolated spore coats, in contrast to whole spores, were lysed by H 2 O 2 even when not pretreated. and the immediate products of spore coat lysis were soluble proteins; on continued incubation with H 2 O 2 these proteins were degraded to low MW peptides and amino acids. It appeared that whole spores resisted lysis because peroxide sensitive bonds were masked by compact tertiary molecular structures, and that the sensitizing agents were able to loosen these structures sufficiently to expose bonds sensitive to H 2 O 2 .