Spore cortex formation in Bacillus subtilis is regulated by accumulation of peptidoglycan precursors under the control of sigma K
Spore cortex formation in Bacillus subtilis is regulated by accumulation of peptidoglycan precursors under the control of sigma K
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DOI：
10.1111/j.1365-2958.2007.05896.x
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发表时间：
2007-09-01
影响因子：
3.6
通讯作者：
Popham, David L.
中科院分区：
文献类型：
--
作者：
Vasudevan, Pradeep;Weaver, Amy;Popham, David L.
细菌内生孢子皮层肽聚糖在发育中的前孢子的双层膜之间合成，是实现孢子脱水和休眠所必需的。枯草芽孢杆菌 spoVB、spoVD 和 spoVE 基因产物在孢子形成早期在母细胞区室中表达，并在皮质合成中发挥作用。在这里，我们发现这些基因的突变阻碍了皮质肽聚糖的合成并导致肽聚糖前体的积累，表明肽聚糖聚合的最早步骤存在缺陷。参与后来激活的 sigma(K) 依赖性母细胞基因表达的 spoIV 基因产物的丢失会导致皮层肽聚糖的合成减少，即使存在较早合成的 SpoV 蛋白，这显然是由于前体生成减少所致。数据显示，可溶性肽聚糖前体的合成增加需要 sigma(K) 的激活，并且蛋白质印迹分析显示前体合成酶 MurAA、MurB、MurC 和 MurF 的增加依赖于 sigma(K) 的激活。总体而言，我们的结果表明，早期孢子形成过程中肽聚糖前体合成的减少，随后在 sigma(K) 激活后重新合成前体，可作为孢子皮层合成时间的调节机制。
The bacterial endospore cortex peptidoglycan is synthesized between the double membranes of the developing forespore and is required for attainment of spore dehydration and dormancy. The Bacillus subtilis spoVB, spoVD and spoVE gene products are expressed in the mother cell compartment early during sporulation and play roles in cortex synthesis. Here we show that mutations in these genes block synthesis of cortex peptidoglycan and cause accumulation of peptidoglycan precursors, indicating a defect at the earliest steps of peptidoglycan polymerization. Loss of spoIV gene products involved in activation of later, sigma(K)-dependent mother cell gene expression results in decreased synthesis of cortex peptidoglycan, even in the presence of the SpoV proteins that were synthesized earlier, apparently due to decreased precursor production. Data show that activation of sigma(K) is required for increased synthesis of the soluble peptidoglycan precursors, and Western blot analyses show that increases in the precursor synthesis enzymes MurAA, MurB, MurC and MurF are dependent on sigma(K) activation. Overall, our results indicate that a decrease in peptidoglycan precursor synthesis during early sporulation, followed by renewed precursor synthesis upon sigma(K) activation, serves as a regulatory mechanism for the timing of spore cortex synthesis.