MOLECULAR MECHANISM OF BACTERIAL SPORE GERMINATION

细菌孢子萌发，这意味着从休眠孢子到营养细胞的分化，由两个主要的生物化学事件组成：对萌发物响应的感觉反应和皮层（孢子肽聚糖）层通过皮层裂解酶的水解反应。本研究的目的是了解裂解酶的活化过程的机制和萌发装置的构建，并获得了以下结果。（一）.与产气荚膜梭菌SleM的胞壁酶功能不同，蜡状芽孢杆菌孢子中的一种新的皮层裂解酶SleL是N-乙酰氨基葡萄糖苷酶，可攻击部分降解的未受应激的皮层。（二）、编码酰胺酶的B sleB的转录受sigma G的调控，SleB B在孢子发育的第III阶段在孢子前室中合成。相反，产气荚膜梭菌SleC（酰胺酶）和SleM在孢子发育的阶段III在母细胞区室中表达。（三）、蜡状B杆菌的SleB和SleL以及产气荚膜梭菌的SleC和SleM均位于休眠孢子皮层的外侧。这些结果明确地表明，发芽paratusis构建在一个物种特异性的方式。（四）、产气荚膜梭菌SleC的N-末端前序列作为分子内分子伴侣来帮助分子的其余部分的折叠。（五）、产气荚膜梭菌SleC在萌发过程中被一组丝氨酸蛋白酶CspA、B和C激活，并且发现sleC和csp基因形成串联排列的簇。

Bacterial spore germination, which means a differentiation from dormant spores to vegetative cells, consists of two major biochemical events ; a sensory reaction which responds to germinants and a hydrolytic reaction of cortex (spore peptidoglycan) layer by cortex lytic enzymes. The present study was undertaken to understand mechanisms of activation process of the lytic enzymes and a construction of germination apparatus, and the following results were obtained.(1). Different from Clostridium perfringens SleM which function as muramidase, a novel cortex lytic enzyme SleL from Bacillus cereus spores acts as N-acetylglucosaminidase which attacks partially degraded unstressed cortex. (2). Transcription of B.cereus sleB which encodes amidase is regulated by sigma G, and SleB is synthesized in forespore compartment at stage III of developing spores. On the contrary, C.perfringens SleC (amidase) and SleM is expressed in mother cell compartment at stage III of developing spores. (3). All SleB and SleL of B.cereus and SleC and SleM of C.perfringens are located at the exterior side of cortex in the dormant spore. These results unequivocally indicate that germination aparatusis constructed in a species-specific manner. (4). The N-terminal presequence of C.perfringens SleC functions as intramolecular chaperone to assist folding of the remainder of molecule. (5). C.perfringens SleC is activated by a group of serineprotease CspA, B and C during germination, and sleC and csp genes were found to form a tandemly aligned cluster.