Department of Ophthalmology, University of Pittsburghgrid.21925.3d School of Medicine, Pittsburgh Pennsylvania, USA.
Infect Immun. 2022 Nov 17;90(11):e0039922. doi: 10.1128/iai.00399-22. Epub 2022 Nov 1.
Bacterial stress response signaling systems, like the Rcs system are triggered by membrane and cell wall damaging compounds, including antibiotics and immune system factors. These regulatory systems help bacteria survive envelope stress by altering the transcriptome resulting in protective phenotypic changes that may also influence the virulence of the bacterium. This study investigated the role of the Rcs stress response system using a clinical keratitis isolate of Serratia marcescens with a mutation in the gene. GumB, an IgaA ortholog, inhibits activation of the Rcs system, such that mutants have overactive Rcs signaling. Transcriptomic analysis indicated that approximately 15% of all S. marcescens genes were significantly altered with 2-fold or greater changes in expression in the Δ mutant compared to the wild type, indicating a global transcriptional regulatory role for GumB. We further investigated the phenotypic consequences of two classes of genes with altered expression in the Δ mutant expected to contribute to infections: serralysin metalloproteases PrtS, SlpB, and SlpE, and type I pili coded by . Secreted fractions from the Δ mutant had reduced cytotoxicity to a corneal cell line, and could be complemented by induced expression of , but not cytolysin , phospholipase , or flagellar master regulator operons. Proteomic analysis, qRT-PCR, and type I pili-dependent yeast agglutination indicated an inhibitory role for the Rcs system in adhesin production. Together these data demonstrate GumB has a global impact on S. marcescens gene expression that had measurable effects on bacterial cytotoxicity and surface adhesin production.
细菌应激反应信号系统，如 Rcs 系统，是由膜和细胞壁损伤化合物触发的，包括抗生素和免疫系统因素。这些调节系统通过改变转录组帮助细菌在 envelope stress 下存活，从而产生保护性表型变化，这些变化也可能影响细菌的毒力。本研究使用带有基因突变的临床角膜炎分离株化脓性链球菌来研究 Rcs 应激反应系统的作用。GumB，一种 IgaA 同源物，抑制 Rcs 系统的激活，使得突变体具有过度活跃的 Rcs 信号。转录组分析表明，大约 15%的所有化脓性链球菌基因在 Δ 突变体中的表达发生了显著改变，与野生型相比，表达变化达到 2 倍或更高，表明 GumB 具有全局转录调控作用。我们进一步研究了两类基因的表型后果，这些基因在 Δ 突变体中的表达发生了改变，预计会导致感染： Serralyisin 金属蛋白酶 PrtS、SlpB 和 SlpE，以及由编码的 I 型菌毛。与野生型相比，Δ 突变体分泌部分对角膜细胞系的细胞毒性降低，并且可以通过诱导表达来互补，但不能通过细胞溶解素、磷脂酶或鞭毛主调节物 operons 来互补。蛋白质组学分析、qRT-PCR 和 I 型菌毛依赖性酵母凝集表明，Rcs 系统在粘附素产生中起抑制作用。这些数据表明 GumB 对化脓性链球菌基因表达具有全局影响，对细菌细胞毒性和表面粘附素产生有可测量的影响。
