School of Chemistry and Molecular Biosciences, the University of Queensland, Brisbane, Queensland, Australia.
Australian Infectious Diseases Research Centre, the University of Queensland, Brisbane, Queensland, Australia.
mBio. 2018 Aug 21;9(4):e01462-18. doi: 10.1128/mBio.01462-18.
Curli are bacterial surface-associated amyloid fibers that bind to the dye Congo red (CR) and facilitate uropathogenic (UPEC) biofilm formation and protection against host innate defenses. Here we sequenced the genome of the curli-producing UPEC pyelonephritis strain MS7163 and showed it belongs to the highly virulent O45:K1:H7 neonatal meningitis-associated clone. MS7163 produced curli at human physiological temperature, and this correlated with biofilm growth, resistance of sessile cells to the human cationic peptide cathelicidin, and enhanced colonization of the mouse bladder. We devised a forward genetic screen using CR staining as a proxy for curli production and identified 41 genes that were required for optimal CR binding, of which 19 genes were essential for curli synthesis. Ten of these genes were novel or poorly characterized with respect to curli synthesis and included genes involved in purine biosynthesis, a regulator that controls the Rcs phosphorelay system, and a novel repressor of curli production (referred to as ). The involvement of these genes in curli production was confirmed by the construction of defined mutants and their complementation. The mutants did not express the curli major subunit CsgA and failed to produce curli based on CR binding. Mutation of (the first gene in the purine biosynthesis pathway) and also led to attenuated colonization of the mouse bladder. Overall, this work has provided new insight into the regulation of curli and the role of these amyloid fibers in UPEC biofilm formation and pathogenesis. Uropathogenic (UPEC) strains are the most common cause of urinary tract infection, a disease increasingly associated with escalating antibiotic resistance. UPEC strains possess multiple surface-associated factors that enable their colonization of the urinary tract, including fimbriae, curli, and autotransporters. Curli are extracellular amyloid fibers that enhance UPEC virulence and promote biofilm formation. Here we examined the function and regulation of curli in a UPEC pyelonephritis strain belonging to the highly virulent O45:K1:H7 neonatal meningitis-associated clone. Curli expression at human physiological temperature led to increased biofilm formation, resistance of sessile cells to the human cationic peptide LL-37, and enhanced bladder colonization. Using a comprehensive genetic screen, we identified multiple genes involved in curli production, including several that were novel or poorly characterized with respect to curli synthesis. In total, this study demonstrates an important role for curli as a UPEC virulence factor that promotes biofilm formation, resistance, and pathogenesis.
卷曲菌是一种细菌表面相关的淀粉样纤维，能与刚果红（CR）结合，并促进尿路致病性（UPEC）生物膜的形成和保护，免受宿主先天防御。在这里，我们对产卷曲菌的 UPEC 肾盂肾炎菌株 MS7163 进行了基因组测序，并表明它属于高毒力 O45：K1：H7 新生儿脑膜炎相关克隆。MS7163 在人体生理温度下产生卷曲菌，这与生物膜生长、游动细胞对人类阳离子肽 cathelicidin 的抗性以及增强对小鼠膀胱的定植有关。我们设计了一个正向遗传筛选实验，用 CR 染色作为卷曲菌产生的替代物，并鉴定了 41 个基因，这些基因对最佳 CR 结合是必需的，其中 19 个基因是卷曲菌合成所必需的。其中 10 个基因与卷曲菌合成有关，是新的或特征描述不佳的，包括参与嘌呤生物合成的基因、控制 Rcs 磷酸传递系统的调节剂，以及卷曲菌产生的一种新型抑制剂（称为）。这些基因在卷曲菌产生中的作用通过构建特定突变体及其互补来确认。突变体不表达卷曲菌主要亚基 CsgA，并且不能基于 CR 结合产生卷曲菌。嘌呤生物合成途径中的第一个基因（）和的突变也导致了小鼠膀胱定植能力减弱。总的来说，这项工作为卷曲菌的调控以及这些淀粉样纤维在 UPEC 生物膜形成和发病机制中的作用提供了新的见解。尿路致病性（UPEC）菌株是尿路感染最常见的原因，这种疾病与抗生素耐药性的不断上升越来越相关。UPEC 菌株具有多种使它们定植于泌尿道的表面相关因子，包括菌毛、卷曲菌和自转运蛋白。卷曲菌是增强 UPEC 毒力并促进生物膜形成的细胞外淀粉样纤维。在这里，我们研究了属于高毒力 O45：K1：H7 新生儿脑膜炎相关克隆的 UPEC 肾盂肾炎菌株中卷曲菌的功能和调控。在人体生理温度下表达卷曲菌会导致生物膜形成增加、游动细胞对人类阳离子肽 LL-37 的抗性增强，以及膀胱定植能力增强。通过全面的遗传筛选，我们鉴定了多个参与卷曲菌产生的基因，其中一些基因与卷曲菌合成有关，是新的或特征描述不佳的。总的来说，这项研究表明卷曲菌是 UPEC 毒力因子的一个重要作用，它促进了生物膜的形成、耐药性和发病机制。
