ACTIVATION OF BACTERIAL ENDOSPORES.

A. Keynan (Israel Institute of Biological Research, Ness Ziona, Israel), Z. Evenchik, H. O. Halvorson, and J. W. Hastings. Studies on the activation of bacterial endospores. J. Bacteriol. 88:313-318. 1964.-Heat activation of bacterial endospores was imitated by suspending spores in reducing agents (mercaptoethanol or thioglycolate) or in a pH less than 4.5. Urea (6 m) had no effect on spores. In addition to the well-known activation at 65 C for 45 min, spores were also activated by exposure to 34 C for 48 hr. The activation by heat and by reducing agents was reversible; the reverse reaction was temperature-dependent. No reversion occurred at -20 C, whereas at 28 C the spores reversed to their original dormant state within 72 hr. It is suggested that the heat-activation phenomenon could be explained by assuming that heat or reducing agents change the tertiary structure of a protein responsible for the maintenance of the dormant state by reducing the disulfide linkages which stabilize the protein in a specific configuration. The partial denaturation of this protein is reversible by reoxidation of the reduced disulfide bonds.