Mechanism on germination and formation of bacterial spores.

食品防腐剂对商业巴氏灭菌难以灭菌的耐热细菌孢子的灭活具有重要意义，从分子水平上了解其萌发机制将有助于食品工业领域的研究。多种证据表明蛋白酶和孢子皮质裂解酶参与了细菌孢子的萌发过程，我们在蜡样芽孢杆菌和Cl的孢子中寻找了这些酶。perfringens。萌发过程中在萌发培养基中释放出一种皮质酶。从蜡样芽孢杆菌中分离得到该酶，其氨基末端序列与已有报道的细胞壁裂解酶无同源性。分离的酶以类似发芽的方式破坏了敏化孢子的肽聚糖，并伴有相变暗。此外，该酶不能分解来自营养细胞的细胞壁肽聚糖。这些观察结果有力地表明，在这里分离的皮质裂解酶是发芽特异性肽聚糖降解酶。在氯的孢子中也发现了一种与该酶非常相似的酶。perfringens。不幸的是，在本实验中没有检测到参与发芽的蛋白酶。但从蜡样芽孢杆菌中分离到2种与枯草菌素性质不同的芽孢相关样枯草菌素酶，且在营养细胞培养中未检出，说明这些蛋白酶是在孢子形成过程中合成的。利用抗皮层裂解酶抗体对孢子中皮层裂解酶的位置及其活化过程进行了研究。

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.