Sensitization of Bacterial Spores to Lysozyme and to Hydrogen Peroxide with Agents which Rupture Disulphide Bonds

Abstract

Spores of species Bacillus and Clostridium were subjected to oxidizing and reducing agents known to rupture protein disulfide bonds and to irradiation (ultraviolet; high speed electron). These treatments caused no loss of brightness of spores when viewed by phase-contrast microscopy. However, lysozyme or hydrogen-peroxide caused phase darkening of treated spores and loss of dipicolinic-acid typical of normal germination except that hydrogen-peroxide eventually caused almost complete lysis of the spores. Under certain conditions, spore viability was unaffected during treatment with reducing agents and during subsequent phase darkening in lysozyme. Spores made susceptible to lysozyme by reducing agents became insusceptible after storage in aerated water. These reactions are compatible with Vinter''s observation of the high content of disulfide bonds in the coast fraction of spores (Vinter, 1960) and with the chemical or physical rupture of these bonds. Rupture of disulfide bonds allows action of lysozyme or hydrogen-peroxide on previously protected substrates. The disulfide bonds are therefore probably important in the resistance of spores to enzymes and irradiation, and rupture of these bonds may be involved in the germination process. The probable location of the lysozyme substrate in mucopeptide of the spore cortex indicates the importance of the integrity of cortex structure in maintaining the phase brightness of spores.