The role of peptidoglycan structure and structural dynamics during endospore dormancy and germination
The role of peptidoglycan structure and structural dynamics during endospore dormancy and germination
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DOI：
10.1023/a:1001800507443
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发表时间：
1999-05-01
影响因子：
2.6
通讯作者：
Foster, SJ
中科院分区：
文献类型：
--
作者：
Atrih, A;Foster, SJ
然而，细菌内生孢子是已知的最具抵抗力的活结构。孢子细胞壁（皮层）保持休眠、核心脱水和耐热性。皮层肽聚糖具有独特的孢子特异性结构，使其能够发挥作用。孢子皮层肽聚糖的交联指数非常低，仅占胞壁酸残基的2.9%，而在营养细胞中为33%。皮层的交联水平可能对维持孢子休眠和耐热性很重要。孢子皮层中约50%的胞壁酸残基被胞壁酸δ-内酰胺取代。这种修饰是孢子特异性的，是皮层的主要特征。胞壁δ-内酰胺在建立核心脱水、保持休眠或耐热性方面没有明显的作用。然而，胞壁δ-内酰胺残基是萌发过程中孢子皮层水解所必需的。它们构成了萌发特异性裂解酶（GSLEs）的底物识别谱的一部分，而GSLEs负责皮层的水解。萌发导致休眠孢子性质的丧失，皮层的水解对于以后的萌发事件和生长是必不可少的。应用muropeptide分析，以确定在发芽过程中的肽聚糖的结构动力学，揭示了一个意想不到的复杂程度的肽聚糖水解。至少有三种水解活性，N-乙酰氨基葡萄糖苷酶，溶解转糖基酶和可能的酰胺酶，涉及。一种非水解活性，可能是胞壁酸的差向异构酶，也发生在萌发早期。溶解转糖基酶产生脱水-胞肽，这些肽在萌发过程中释放，并可能在生长过程中再循环，形成新的营养细胞壁的一部分。
Dormant, bacterial endospores are the most resistant living structures known. The spore cell wall (cortex) maintains dormancy, core dehydration, and heat resistance. The cortex peptidoglycan has a unique, spore specific structure that enables it to fulfill its role. The cross-linking index of spore cortex peptidoglycan is very low, occurring at only 2.9% of the muramic acid residues compared to 33% in vegetative cells. The level of cross-linking of the cortex may be important in maintaining spore dormancy and heat resistance. Approximately 50% of the muramic acid residues in spore cortex are substituted with muramic delta-lactam. This modification is spore specific and is the major characteristic feature of the cortex. The muramic delta-lactam has no apparent role in establishing core dehydration, maintaining dormancy or heat resistance. However, the muramic delta-lactam residues are necessary for spore cortex hydrolysis during germination. They constitute part of the substrate recognition profile of the germination specific lytic enzymes (GSLEs) which are responsible for cortex hydrolysis.Germination results in loss of dormant spore properties and hydrolysis of the cortex is essential for later germination events and outgrowth. Application of muropeptide analysis to determine peptidoglycan structural dynamics during germination has revealed an unexpected degree of complexity in peptidoglycan hydrolysis. At least three hydrolytic activities, an N-acetyl glucosaminidase, a lytic transglycosylase and a possible amidase, are involved. A non-hydrolytic acitivity, likely to be an epimerase of muramic acid also occurs early during germination.The lytic transglycosylase generates anhydro-muropeptides which are released during germination and may be recycled during outgrowth to form part of the new vegetative cell wall.