Harris-Jones Tiffany N, Medina Krizia M Pérez, Hackett Kathleen T, Schave Melanie A, Schaub Ryan E, Dillard Joseph P
Department of Medical Microbiology and Immunology, University of Wisconsin-Madison School of Medicine and Public Health.
bioRxiv. 2023 Aug 24:2023.08.23.554517. doi: 10.1101/2023.08.23.554517.
Infection with the Gram-negative species leads to inflammation that is responsible for the disease symptoms of gonococcal urethritis, cervicitis, and pelvic inflammatory disease. During growth these bacteria release significant amounts of peptidoglycan (PG) fragments which elicit inflammatory responses in the human host. To better understand the mechanisms involved in PG synthesis and breakdown in , we characterized the effects of mutation of . MltG has been identified in other bacterial species as a terminase that stops PG strand growth by cleaving the growing glycan. Mutation of in did not affect bacterial growth rate but resulted in increased PG turnover, more cells of large size, decreased autolysis under non-growth conditions, and increased sensitivity to antibiotics that affect PG crosslinking. An mutant released greatly increased amounts of PG monomers, PG dimers, and larger oligomers. In the background, mutation of either or , encoding the lytic transglycosylases responsible for PG monomer liberation, resulted in wild-type levels of PG monomer release. Bacterial two-hybrid assays identified positive interactions of MltG with synthetic penicillin-binding proteins PBP1 and PBP2 and the PG-degrading endopeptidase PBP4 (PbpG). These data are consistent with MltG acting as a terminase in and suggest that absence of MltG activity results in excessive PG growth and extra PG in the sacculus that must be degraded by lytic transglycosylases including LtgA and LtgD. Furthermore, absence of MltG causes a cell wall defect that is manifested as large cell size and antibiotic sensitivity.
革兰氏阴性菌感染会引发炎症,这种炎症是淋菌性尿道炎、宫颈炎和盆腔炎等疾病症状的成因。在生长过程中,这些细菌会释放大量肽聚糖(PG)片段,从而在人类宿主中引发炎症反应。为了更好地理解[细菌名称]中PG合成和分解所涉及的机制,我们对[基因名称]突变的影响进行了表征。在其他细菌物种中,MltG已被鉴定为一种终止酶,它通过切割正在生长的聚糖来停止PG链的生长。[细菌名称]中[基因名称]的突变并不影响细菌的生长速率,但会导致PG周转增加、更多大尺寸细胞、在非生长条件下自溶减少以及对影响PG交联的抗生素敏感性增加。一个[突变体名称]突变体释放出大量增加的PG单体、PG二聚体和更大的寡聚体。在[细菌名称]背景下,编码负责释放PG单体的溶菌转糖基酶的[基因名称1]或[基因名称2]的突变导致PG单体释放水平恢复到野生型。细菌双杂交试验确定了MltG与合成青霉素结合蛋白PBP1和PBP2以及PG降解内肽酶PBP4(PbpG)之间存在正向相互作用。这些数据与MltG在[细菌名称]中作为终止酶的作用一致,并表明缺乏MltG活性会导致PG过度生长以及在细胞壁中产生额外的PG,这些额外的PG必须由包括LtgA和LtgD在内的溶菌转糖基酶降解。此外,缺乏MltG会导致细胞壁缺陷,表现为细胞尺寸增大和对抗生素敏感。