Duchêne Marie-Clémence, Rolain Thomas, Knoops Adrien, Courtin Pascal, Chapot-Chartier Marie-Pierre, Dufrêne Yves F, Hallet Bernard F, Hols Pascal
Louvain Institute of Biomolecular Science and Technology, Université Catholique de Louvain, Louvain-La-Neuve, Belgium.
Micalis Institute, INRA, AgroParisTech, Université Paris-Saclay, Jouy-en-Josas, France.
Front Microbiol. 2019 Apr 12;10:713. doi: 10.3389/fmicb.2019.00713. eCollection 2019.
Peptidoglycan (PG) is an essential lattice of the bacterial cell wall that needs to be continuously remodeled to allow growth. This task is ensured by the concerted action of PG synthases that insert new material in the pre-existing structure and PG hydrolases (PGHs) that cleave the PG meshwork at critical sites for its processing. Contrasting with that contains more than 35 PGHs, is a non-sporulating rod-shaped bacterium that is predicted to possess a minimal set of 12 PGHs. Their role in morphogenesis and cell cycle remains mostly unexplored, except for the involvement of the glucosaminidase Acm2 in cell separation and the NlpC/P60 D, L-endopeptidase LytA in cell shape maintenance. Besides LytA, encodes three additional NlpC/P60 endopeptidases (i.e., LytB, LytC and LytD). The analysis of these four endopeptidases suggests that they could have redundant functions based on their modular organization, forming two pairs of paralogous enzymes. In this work, we investigate the role of each Lyt endopeptidase in cell morphogenesis in order to evaluate their distinct or redundant functions, and eventually their synthetic lethality. We show that the paralogous LytC and LytD enzymes are not required for cell shape maintenance, which may indicate an accessory role such as in PG recycling. In contrast, LytA and LytB appear to be key players of the cell cycle. We show here that LytA is required for cell elongation while LytB is involved in the spatio-temporal regulation of cell division. In addition, both PGHs are involved in the proper positioning of the division site. The absence of LytA activity is responsible for the asymmetrical positioning of septa in round cells while the lack of LytB results in a lateral misplacement of division planes in rod-shaped cells. Finally, we show that the co-inactivation of LytA and LytB is synthetically affecting cell growth, which confirms the key roles played by both enzymes in PG remodeling during the cell cycle of . Based on the large distribution of NlpC/P60 endopeptidases in low-GC Gram-positive bacteria, these enzymes are attractive targets for the discovery of novel antimicrobial compounds.
肽聚糖(PG)是细菌细胞壁的一种必需晶格结构,需要不断重塑以支持生长。这项任务由PG合成酶和PG水解酶(PGHs)的协同作用来确保,PG合成酶负责在已有结构中插入新的物质,而PG水解酶则在关键位点切割PG网络以进行加工。与含有超过35种PGH的细菌不同,[细菌名称]是一种非芽孢形成的杆状细菌,预计仅拥有最少的12种PGH。除了氨基葡萄糖苷酶Acm2参与细胞分裂以及NlpC/P60 D,L-内肽酶LytA参与细胞形状维持外,它们在形态发生和细胞周期中的作用大多仍未被探索。除LytA外,[细菌名称]还编码另外三种NlpC/P60内肽酶(即LytB、LytC和LytD)。对这四种内肽酶的分析表明,基于它们的模块化组织,它们可能具有冗余功能,形成两对同源酶。在这项工作中,我们研究了每种Lyt内肽酶在细胞形态发生中的作用,以评估它们各自或冗余的功能,以及最终它们的合成致死性。我们发现同源的LytC和LytD酶对于细胞形状维持并非必需,这可能表明它们具有辅助作用,例如参与PG循环利用。相比之下,LytA和LytB似乎是细胞周期的关键参与者。我们在此表明,LytA是细胞伸长所必需的,而LytB参与细胞分裂的时空调节。此外,这两种PGH都参与分裂位点的正确定位。缺乏LytA活性会导致圆形细胞中隔膜的不对称定位,而缺乏LytB则会导致杆状细胞中分裂平面的侧向错位。最后,我们表明LytA和LytB的共同失活会综合影响细胞生长,这证实了这两种酶在[细菌名称]细胞周期中PG重塑过程中所起的关键作用。基于NlpC/P60内肽酶在低GC革兰氏阳性细菌中的广泛分布,这些酶是发现新型抗菌化合物的有吸引力的靶点。