LytM-Domain Factors Are Required for Daughter Cell Separation and Rapid Ampicillin-Induced Lysis in Escherichia coli
LytM-Domain Factors Are Required for Daughter Cell Separation and Rapid Ampicillin-Induced Lysis in Escherichia coli
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DOI：
10.1128/jb.00505-09
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发表时间：
2009-08-15
影响因子：
3.2
通讯作者：
Bernhardt, Thomas G.
中科院分区：
文献类型：
--
作者：
Uehara, Tsuyoshi;Dinh, Thuy;Bernhardt, Thomas G.
细菌胞质分裂与新肽聚糖（PG）在分裂位点的局部合成偶联。这种新产生的隔PG最初由子细胞共享。在大肠杆菌和其他革兰氏阴性细菌中，它在产生后不久就分裂，以促进子细胞分离，并允许外膜收缩紧密跟随内膜收缩。我们发现，含有溶葡萄球菌酶（LytM）结构域的E.大肠杆菌（EnvC、NlpD、YgeR和YebA）中的细胞是分隔PG分裂和子细胞分离所绝对需要的。缺乏所有LytM因子的突变体形成长细胞链，其中隔膜含有一层未分裂的PG。与这些因子在隔膜PG分裂中起直接作用一致，发现EnvC-mCherry和NlpD-mCherry融合体都被特异性地募集到分裂位点。我们还发现了LytM结构域因子在β-内酰胺诱导的细胞裂解过程中的作用。与野生型细胞相比，缺乏LytM结构域因子的突变体在用氨苄青霉素处理后细胞溶解的发生延迟。此外，LytM（-）细胞不是像野生型细胞那样从中细胞病变中溶解，而是通过逐渐丧失细胞形状和完整性来溶解。总体而言，缺乏LytM结构域因子的突变体的表型与N-乙酰胞壁酰-L-丙氨酸酰胺酶缺陷的突变体的表型具有惊人的相似性：AmiA、AmiB和AmiC。E.因此，大肠杆菌似乎依赖于两组不同的推定PG水解酶来促进适当的细胞分裂。
Bacterial cytokinesis is coupled to the localized synthesis of new peptidoglycan (PG) at the division site. This newly generated septal PG is initially shared by the daughter cells. In Escherichia coli and other gram-negative bacteria, it is split shortly after it is made to promote daughter cell separation and allow outer membrane constriction to closely follow that of the inner membrane. We have discovered that the LytM (lysostaphin)domain containing factors of E. coli (EnvC, NlpD, YgeR, and YebA) are absolutely required for septal PG splitting and daughter cell separation. Mutants lacking all LytM factors form long cell chains with septa containing a layer of unsplit PG. Consistent with these factors playing a direct role in septal PG splitting, both EnvC-mCherry and NlpD-mCherry fusions were found to be specifically recruited to the division site. We also uncovered a role for the LytM-domain factors in the process of beta-lactam-induced cell lysis. Compared to wild-type cells, mutants lacking LytM-domain factors were delayed in the onset of cell lysis after treatment with ampicillin. Moreover, rather than lysing from midcell lesions like wild-type cells, LytM(-) cells appeared to lyse through a gradual loss of cell shape and integrity. Overall, the phenotypes of mutants lacking LytM- domain factors bear a striking resemblance to those of mutants defective for the N-acetylmuramyl-L-alanine amidases: AmiA, AmiB, and AmiC. E. coli thus appears to rely on two distinct sets of putative PG hydrolases to promote proper cell division.