Amino acids in the Bacillus subtilis morphogenetic protein SpoIVA with roles in spore coat and cortex formation
Amino acids in the Bacillus subtilis morphogenetic protein SpoIVA with roles in spore coat and cortex formation
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DOI：
10.1128/jb.183.5.1645-1654.2001
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发表时间：
2001-03-01
影响因子：
3.2
通讯作者：
Driks, A
中科院分区：
文献类型：
--
作者：
Catalano, FA;Meador-Parton, J;Driks, A
细菌孢子被一层蛋白质外壳和一层称为皮层的特殊肽聚糖保护着不受环境的影响。在枯草芽孢杆菌中，孢子表面被膜的附着和皮层的合成都依赖于孢子蛋白SpoIVA。为了鉴定SpoIVA的功能上重要的氨基酸，我们产生并表征了具有导致外壳和皮层形成缺陷的SpoIVA随机点突变的菌株。一个突变体类似于无效突变体，因为该菌株的孢子形成细胞缺乏皮层，并且外壳在周围的细胞质中形成漩涡，而不是围绕孢子的壳。我们确定了第二类的六个突变体的孢子装配的部分缺陷。在这些菌株的孢子形成细胞中，我们经常观察到在同一细胞中，除了孢子周围的被膜外，还有错误定位的被膜的漩涡。使用免疫荧光显微镜，我们发现，在这些突变体中的两个，SpoIVA未能本地化的孢子，而在其余的菌株，本地化在很大程度上是正常的。这些突变鉴定了参与SpoIVA靶向孢子和附着外壳的氨基酸。我们还分离出了大量的突变体，它们产生的孢子无法保持脱水状态。对该类中的一个突变体的分析表明，该菌株的孢子积累的肽聚糖水平降低，结构改变。
Bacterial spores are protected from the environment by a proteinaceous coat and a layer of specialized peptidoglycan called the cortex. In Bacillus subtilis, the attachment of the coat to the spore surface and the synthesis of the cortex both depend on the spore protein SpoIVA. To identify functionally important amino acids of SpoIVA, we generated and characterized strains bearing random point mutations of spoIVA that result in defects in coat and cortex formation. One mutant resembles the null mutant, as sporulating cells of this strain lack the cortex and the coat forms a swirl in the surrounding cytoplasm instead of a shell around the spore. We identified a second class of six mutants with a partial defect in spore assembly. In sporulating cells of these strains, we frequently observed swirls of mislocalized coat in addition to a coat surrounding the spore, in the same cell. Using immunofluorescence microscopy, we found that in two of these mutants, SpoIVA fails to localize to the spore, whereas in the remaining strains, localization is largely normal. These mutations identify amino acids involved in targeting of SpoIVA to the spore and in attachment of the coat. We also isolated a large set of mutants producing spores that are unable to maintain the dehydrated state. Analysis of one mutant in this class suggests that spores of this strain accumulate reduced levels of peptidoglycan with an altered structure.