Park Sohee, Cho Hongbaek
Department of Biological Sciences, College of Natural Sciences, Sungkyunkwan University, Suwon, South Korea.
Front Microbiol. 2022 May 3;13:891926. doi: 10.3389/fmicb.2022.891926. eCollection 2022.
The Tol-Pal system is a transenvelope complex widely conserved among Gram-negative bacteria. It is recruited to the septal ring during cytokinesis, and its inactivation causes pleiotropic phenotypes mainly associated with the division process. From our genetic screen to identify factors required for delaying lysis upon treatment of beta lactams, we discovered that the mutant shares similar defects with mutants of the major class A PBP system (PBP1b-LpoB) in terms of lysis prevention. Further phenotypic analyses revealed that the Tol-Pal system plays an important role in maintaining cell integrity not only during septation, but also during cell elongation. Simultaneous inactivation of the Tol-Pal system and the PBP1b-LpoB system leads to lysis during cell elongation as well as during division. Moreover, production of the Lpo activator-bypass PBP1b, but not wild-type PBP1b, partially suppressed the Tol-Pal defect in maintaining cell integrity upon treatment of mecillinam specific for the Rod system, suggesting that the Tol-Pal system is likely to be involved in the activation of aPBP by Lpo factors. Overall, our results indicate that the Tol-Pal system plays an important role in maintaining cell wall integrity during elongation in addition to its multifaceted roles during cytokinesis.
Tol-Pal系统是一种广泛存在于革兰氏阴性菌中的跨膜复合体。在胞质分裂过程中，它被募集到隔膜环上，其失活会导致多效性表型，主要与分裂过程相关。通过我们的遗传筛选来鉴定在β-内酰胺处理后延迟裂解所需的因子，我们发现该突变体在防止裂解方面与主要的A类青霉素结合蛋白系统（PBP1b-LpoB）的突变体具有相似的缺陷。进一步的表型分析表明，Tol-Pal系统不仅在隔膜形成过程中，而且在细胞伸长过程中，在维持细胞完整性方面都起着重要作用。Tol-Pal系统和PBP1b-LpoB系统同时失活会导致细胞在伸长和分裂过程中裂解。此外，产生Lpo激活剂旁路PBP1b而非野生型PBP1b，部分抑制了在美西林处理（对Rod系统具有特异性）时Tol-Pal系统在维持细胞完整性方面的缺陷，这表明Tol-Pal系统可能参与Lpo因子对aPBP的激活。总体而言，我们的结果表明，Tol-Pal系统除了在胞质分裂过程中具有多方面作用外，在细胞伸长过程中维持细胞壁完整性方面也起着重要作用。
