Wang Jinglan, Alvarez Laura, Bulgheresi Silvia, Cava Felipe, den Blaauwen Tanneke
Bacterial Cell Biology & Physiology, Faculty of Science, Swammerdam Institute for Life Sciences, University of Amsterdam, Science Park 904, 1098 XH Amsterdam, The Netherlands.
Department of Molecular Biology, Umeå University, SE-901 87 Umeå, Sweden.
Antibiotics (Basel). 2021 Mar 9;10(3):274. doi: 10.3390/antibiotics10030274.
Peptidoglycan (PG) is essential for bacterial survival and maintaining cell shape. The rod-shaped model bacterium has a set of seven endopeptidases that remodel the PG during cell growth. The gamma proteobacterium Thiosymbion oneisti is also rod-shaped and attaches to the cuticle of its nematode host by one pole. It widens and divides by longitudinal fission using the canonical proteins MreB and FtsZ. The PG layer of . T. oneisti has an unusually high peptide cross-linkage of 67% but relatively short glycan chains with an average length of 12 disaccharides. Curiously, it has only two predicted endopeptidases, MepA and PBP4. Cellular localization of symbiont PBP4 by fluorescently labeled antibodies reveals its polar localization and its accumulation at the constriction sites, suggesting that PBP4 is involved in PG biosynthesis during septum formation. Isolated symbiont PBP4 protein shows a different selectivity for β-lactams compared to its homologue from . Bocillin-FL binding by PBP4 is activated by some β-lactams, suggesting the presence of an allosteric binding site. Overall, our data point to a role of PBP4 in PG cleavage during the longitudinal cell division and to a PG that might have been adapted to the symbiotic lifestyle.
肽聚糖（PG）对于细菌存活和维持细胞形态至关重要。杆状模式细菌有一组七种内肽酶，在细胞生长过程中重塑肽聚糖。γ-变形菌纲的硫共生菌Thiosymbion oneisti也是杆状的，通过一极附着于其线虫宿主的角质层。它利用典型蛋白MreB和FtsZ通过纵向分裂进行增宽和分裂。Thiosymbion oneisti的肽聚糖层具有异常高的67%的肽交联，但聚糖链相对较短，平均长度为12个二糖。奇怪的是，它只有两种预测的内肽酶，MepA和PBP4。通过荧光标记抗体对共生体PBP4进行细胞定位，揭示了其极性定位及其在缢缩位点的积累，表明PBP4在隔膜形成过程中参与肽聚糖生物合成。与来自[未提及的物种]的同源物相比，分离出的共生体PBP4蛋白对β-内酰胺显示出不同的选择性。PBP4与Bocillin-FL的结合被一些β-内酰胺激活，表明存在变构结合位点。总体而言，我们的数据表明PBP4在纵向细胞分裂过程中参与肽聚糖切割，并且表明肽聚糖可能已经适应了共生生活方式。
