Unstable Escherichia coli L forms revisited: Growth requires peptidoglycan synthesis
Unstable Escherichia coli L forms revisited: Growth requires peptidoglycan synthesis
复制标题
DOI：
10.1128/jb.00273-07
复制
发表时间：
2007-09-01
影响因子：
3.2
通讯作者：
D'Ari, Richard
中科院分区：
文献类型：
--
作者：
Joseleau-Petit, Daniele;Liebart, Jean-Claude;D'Ari, Richard
尽管细胞分裂通常与隔膜肽聚糖的合成密不可分，但生长中的细菌 L 型被认为缺乏肽聚糖。为了探索 L 型使用哪些细胞分裂功能，我们建立了一个方案，通过使用青霉素结合蛋白 (PBP) 1A 和 1B 的特异性抑制剂 P-内酰胺头孢磺啶，将野生型大肠杆菌 K-12 菌株的培养物过夜定量转化为 L 型生长状态。在含有头孢磺啶的丰富高渗培养基中，所有细胞都是球形且对渗透敏感，就像经典的 L 形式一样。然而，令人惊讶的是，突变体研究表明集落形成需要 D-谷氨酸、二氨基庚二酸和 MurA 活性，所有这些都是肽聚糖合成所特有的。高效液相色谱分析证实，这些L型样细胞含有肽聚糖，含量为正常值的7%。此外，β-内酰胺哌拉西林是细胞分裂蛋白 PBP 3 的特异性抑制剂，可迅速阻断这些 L 型样细胞的细胞分裂。同样，青霉素诱导的 L 型样细胞仅在富含高渗平板的琼脂层内生长，也需要 D-谷氨酸、二氨基庚二酸和 MurA 活性。这些结果强烈表明，头孢磺啶和青霉素诱导的大肠杆菌 L 型样细胞（可能是所有 L 型）具有残留的肽聚糖合成，这对于它们的生长至关重要，可能是细胞分裂所必需的。
Growing bacterial L forms are reputed to lack peptidoglycan, although cell division is normally inseparable from septal peptidoglycan synthesis. To explore which cell division functions L forms use, we established a protocol for quantitatively converting a culture of a wild-type Escherichia coli K-12 strain overnight to a growing L-form-like state by use of the P-lactam cefsulodin, a specific inhibitor of penicillin-binding proteins (PBPs) 1A and 1B. In rich hypertonic medium containing cefsulodin, all cells are spherical and osmosensitive, like classical L forms. Surprisingly, however, mutant studies showed that colony formation requires D-glutamate, diaminopimelate, and MurA activity, all of which are specific to peptidoglycan synthesis. High-performance liquid chromatography analysis confirmed that these L-form-like cells contain peptidoglycan, with 7% of the normal amount. Moreover, the P-lactam piperacillin, a specific inhibitor of the cell division protein PBP 3, rapidly blocks the cell division of these L-form-like cells. Similarly, penicillin-induced L-form-like cells, which grow only within the agar layers of rich hypertonic plates, also require D-glutamate, diaminopimelate, and MurA activity. These results strongly suggest that cefsulodin- and penicillin-induced L-form-like cells of E. coli-and possibly all L forms-have residual peptidoglycan synthesis which is essential for their growth, probably being required for cell division.