Department of Microbiology and Biotechnology Centre, The Maharaja Sayajirao University of Baroda, Vadodara, Gujarat, 390002, India.
Microbiol Res. 2021 Sep;250:126785. doi: 10.1016/j.micres.2021.126785. Epub 2021 May 5.
Pathogenesis of Staphylococcus aureus is attributed to its remarkable adaptation to changes in the environment, mediated by the arsenal of virulence factors, which are regulated by intricate mechanisms that include small RNAs (sRNAs) as important regulatory molecules. The sRNA SprX was previously described to be involved in the regulation of S. aureus pathogenicity, by modifying the expression of surface-associated clumping factor B and the secreted delta haemolysin. This study describes the regulation by SprX, of expression of multiple autolysins, which play an essential role in cell wall metabolism and function as important virulence factors that facilitate adhesion, internalization, and immune evasion during S. aureus colonization and pathogenesis. SprX acts by positively regulating the expression of autolysin regulator WalR. Overexpression of SprX resulted in differential regulation of autolysins IsaA, and LytM, while WalR levels were unchanged. SprX knockdown strain exhibited down-regulation of multiple autolytic bands corresponding to the major autolysin AtlA and its process intermediates in cell wall degradation zymography, and 0.2 to 0.1 fold reduction of lytM, atlA, isaA, and walR transcripts in qRT-PCRs. Down-regulation of SprX resulted in altered phenotype with high cell aggregation as analyzed by SEM, decrease in biofilm formation and higher resistance to Triton X-100-induced lysis, all of which indicate that SprX is essential for expression of autolysins. A putative RNA-RNA interaction was indicated in silico between SprX and walR mRNA and further confirmed by in vitro RNA-RNA interaction in electrophoretic mobility shift assays. These findings elucidate a new mechanism in which SprX modulates the S. aureus pathogenicity by regulating the regulator of autolysins in cell wall metabolism and as virulence factors.
金黄色葡萄球菌的发病机制归因于其对环境变化的显著适应能力，这是由其丰富的毒力因子介导的，这些毒力因子的表达受到复杂机制的调控，其中包括小 RNA（sRNA）等重要的调节分子。先前的研究表明，sRNA SprX 参与了金黄色葡萄球菌致病性的调节，通过调节表面相关聚集因子 B 和分泌的δ-溶血素的表达来实现。本研究描述了 SprX 对多种自溶素表达的调节作用，这些自溶素在细胞壁代谢中发挥着重要作用，并且作为重要的毒力因子，有助于金黄色葡萄球菌定植和发病过程中的黏附、内化和免疫逃避。SprX 通过正调控自溶素调节因子 WalR 的表达来发挥作用。SprX 的过表达导致自溶素 IsaA 和 LytM 的表达发生差异调节，而 WalR 水平不变。SprX 敲低菌株表现出多种自溶酶带的下调，这些自溶酶带对应于主要自溶素 AtlA 及其细胞壁降解同工酶中的中间产物，并且 qRT-PCR 分析显示 lytM、atlA、isaA 和 walR 转录物的表达水平降低了 0.2 到 0.1 倍。SprX 的下调导致 SEM 分析中细胞聚集增加的表型改变，生物膜形成减少，以及对 Triton X-100 诱导裂解的抗性增加，所有这些都表明 SprX 对自溶素的表达是必需的。计算机模拟表明 SprX 和 WalR mRNA 之间存在 RNA-RNA 相互作用，并且在电泳迁移率变动分析中的体外 RNA-RNA 相互作用实验进一步证实了这一点。这些发现阐明了一种新的机制，即 SprX 通过调节细胞壁代谢中的自溶素调节因子和作为毒力因子来调节金黄色葡萄球菌的致病性。
