Mechanism on germination and formation of bacterial spores.

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It is of importance for food preservatives to inactivate heat-resistant bacterial spores which are hardly sterilized under commercial pasteurization, and the understanding of germination mechanism in molecular level should be helpful in the field of food industry.Several lines of evidence had indicated that protease and spore-cortex lytic enzyme are involved in the germination process of bacterial spores, and we looked for those enzymes in spores of B. cereus and Cl. perfringens. A cortex lytic enzyme was released in the germination medium during germination. The enzyme from B. cereus was purified and its amino-terminal sequence determined did not show any homology with those of cell wall lytic enzyme reported so far. The isolated enzyme disrupted peptidoglycan of sensitized-spores accompanying with a phase darkening, in a manner similar to germination. Furthermore, the enzyme was incapable of decomposing peptidoglycan of cell wall derived from vegetative cells. These observations strongly indicate that the cortex lytic enzyme isolated here is germination-specific peptidoglycan-degrading enzyme. An enzyme showing quite similar characteristics to the enzyme was also detected in spores of Cl. perfringens. Unfortunately, protease involved in germination was not detected in the present experiment. However, 2 types of spore-associated subtilisin-like enzyme were isolated from B. cereus, which differ in the properties from subtilisin, and those enzyme were not detected in the culture of vegetative cells, suggesting that the proteases were synthesized during sporulation. Studies on the location of cortex lytic enzyme in spores and on its activation process are in progress using anti-cortex lytic enzyme antibody.