细菌的生长和分裂依赖于形态发生复合物的复杂调节来重塑细胞包膜而不损害包膜完整性。近年来,在了解细胞壁代谢酶的调节方面取得了重大进展。然而,其他细胞包膜成分也在形态发生中起作用。在低渗透压环境中保护包膜完整性所需的主要因素是OpgH,渗透调节周质葡聚糖(OPGs)的合酶。这里,我们证明OpgH在α-蛋白细菌中必不可少。出乎意料的是,耗尽OpgH或尝试用催化死亡的OpgH变体进行补充导致显著的不对称膨胀和细胞裂解。这些形状缺陷伴随着细胞壁合成的减少和形态发生复合物的错误定位。有趣的是,CenKR双组分系统的过度激活与α-蛋白细菌表型中的细胞包膜应激稳态有关,与OpgH耗竭相关的形态发生缺陷。这些扰动中的每一个都导致延长体蛋白水平的增加,MreB,以及分裂体蛋白FtsZ和MipZ以及OpgH的水平降低,本身。在CenKR过度激活期间,OpgH的组成型产生可防止细胞膨胀,但是细胞仍然表现出形态发生缺陷。我们建议OPG消耗激活CenKR,导致细胞包膜相关基因表达的变化,但是OPGs也对形态发生产生不依赖CenKR的影响。我们的数据确立了OpgH同系物在形态发生中的令人惊讶的功能,并揭示了OpgH在维持杆菌属细胞形态中的重要作用。重要细菌必须以严格调节的方式合成和强化细胞包膜,以协调生长和适应。渗透调节的周质葡聚糖(OPGs)是重要的,但却知之甚少,革兰氏阴性细胞包膜的成分,有助于包膜完整性并防止渗透应激。这里,我们确定OPG合酶OpgH发挥了令人惊讶的作用,在结球菌形态发生中的重要作用。OpgH的丢失通过对形态发生复合物的定位和活性的错误调节而导致不对称的细胞膨胀和裂解。CenKR双组分系统的过度激活参与包膜稳态表型的OpgH耗竭,表明OpgH的消耗激活了CenKR。因为细胞包膜的完整性对细菌的生存至关重要,了解OpgH活性如何有助于形态发生和包膜完整性的维持可能有助于抗生素疗法的开发。
Bacterial growth and division rely on intricate regulation of morphogenetic complexes to remodel the cell envelope without compromising envelope integrity. Significant progress has been made in recent years towards understanding the regulation of cell wall metabolic enzymes. However, other cell envelope components play a role in morphogenesis as well. A primary factor required to protect envelope integrity in low osmolarity environments is OpgH, the synthase of osmoregulated periplasmic glucans (OPGs). Here, we demonstrate that OpgH is essential in the α-proteobacterium Caulobacter crescentus. Unexpectedly, depletion of OpgH or attempted complementation with a catalytically dead OpgH variant results in striking asymmetric bulging and cell lysis. These shape defects are accompanied by reduced cell wall synthesis and mislocalization of morphogenetic complexes. Interestingly, overactivation of the CenKR two-component system that has been implicated in cell envelope stress homeostasis in α-proteobacteria phenocopies the morphogenetic defects associated with OpgH depletion. Each of these perturbations leads to an increase in the levels of the elongasome protein, MreB, and decreases in the levels of
divisome proteins FtsZ and MipZ as well as OpgH, itself. Constitutive production of OpgH during CenKR overactivation prevents cell bulging, but cells still exhibit morphogenetic defects. We propose that OPG depletion activates CenKR, leading to changes in the expression of cell envelope-related genes, but that OPGs also exert CenKR-independent effects on morphogenesis. Our data establish a surprising function for an OpgH homolog in morphogenesis and reveal an essential role of OpgH in maintaining cell morphology in Caulobacter.IMPORTANCEBacteria must synthesize and fortify the cell envelope in a tightly regulated manner to orchestrate growth and adaptation. Osmoregulated periplasmic glucans (OPGs) are important, but poorly understood, constituents of Gram-negative cell envelopes that contribute to envelope integrity and protect against osmotic stress. Here, we determined that the OPG synthase OpgH plays a surprising, essential role in morphogenesis in Caulobacter crescentus. Loss of OpgH causes asymmetric cell bulging and lysis via misregulation of the localization and activity of morphogenetic complexes. Overactivation of the CenKR two-component system involved in envelope homeostasis phenocopies OpgH depletion, suggesting that depletion of OpgH activates CenKR. Because cell envelope integrity is critical for bacterial survival, understanding how OpgH activity contributes to morphogenesis and maintenance of envelope integrity could aid in the development of antibiotic therapies.