Department of Oral Biology, Rady Faculty of Health Sciences, Dr. Gerald Niznick College of Dentistry, University of Manitoba, Winnipeg, MB R3E 0W2, Canada.
College of Life Sciences, Northwest University, Xi'an 710069, China.
Int J Mol Sci. 2021 Nov 22;22(22):12561. doi: 10.3390/ijms222212561.
The opportunistic pathogen is a significant cause of infection in immunocompromised individuals, cystic fibrosis patients, and burn victims. To benefit its survival, the bacterium adapt to either a motile or sessile lifestyle when infecting the host. The motile bacterium has an often activated type III secretion system (T3SS), which is virulent to the host, whereas the sessile bacterium harbors an active T6SS and lives in biofilms. Regulatory pathways involving Gac-Rsm or secondary messengers such as c-di-GMP determine which lifestyle is favorable for . Here, we introduce the RNA binding protein RtcB as a modulator of the switch between motile and sessile bacterial lifestyles. Using the wild-type PAO1, and a mutant PAO1(∆) in which T3SS is repressed and T6SS active, we show that deleting led to simultaneous expression of T3SS and T6SS in both PAO1(∆) and PAO1(∆∆). The deletion of also increased biofilm formation in PAO1(∆) and restored the motility of PAO1(∆∆). RNA-sequencing data suggested RtcB as a global modulator affecting multiple virulence factors, including bacterial secretion systems. Competitive killing and infection assays showed that the three T6SS systems (H1, H2, and H3) in PAO1(∆) were activated into a functional syringe, and could compete with and effectively infect lettuce. Western blotting and RT-PCR results showed that RtcB probably exerted its function through RsmA in PAO1(∆∆). Quantification of c-di-GMP showed an elevated intracellular levels in PAO1(∆), which likely drove the switch between T6SS and T3SS, and contributed to the altered phenotypes and characteristics observed. Our data demonstrate a pivotal role of RtcB in the virulence of by controlling multiple virulence determinants, such as biofilm formation, motility, pyocyanin production, T3SS, and T6SS secretion systems towards eukaryotic and prokaryotic cells. These findings suggest RtcB as a potential target for controlling colonization, establishment, and pathogenicity.
机会性病原体是免疫功能低下个体、囊性纤维化患者和烧伤患者感染的重要原因。为了生存，细菌在感染宿主时会适应游动或定殖生活方式。游动细菌通常具有激活的 III 型分泌系统（T3SS），对宿主具有毒性，而定殖细菌则具有活跃的 T6SS 并生活在生物膜中。涉及 Gac-Rsm 或 c-di-GMP 等二级信使的调节途径决定了哪种生活方式对 有利。在这里，我们介绍 RNA 结合蛋白 RtcB 作为调节细菌游动和定殖生活方式之间转换的调节剂。使用野生型 PAO1 和 T3SS 被抑制但 T6SS 活跃的 突变体 PAO1(∆)，我们表明，删除 导致 PAO1(∆)和 PAO1(∆∆)中同时表达 T3SS 和 T6SS。 缺失还增加了 PAO1(∆)中的生物膜形成，并恢复了 PAO1(∆∆)的运动性。RNA 测序数据表明 RtcB 是一种全局调节剂，影响包括细菌分泌系统在内的多种毒力因子。竞争杀伤和感染测定表明，PAO1(∆)中的三个 T6SS 系统（H1、H2 和 H3）被激活为功能性注射器，并且可以与 和有效感染生菜竞争。Western blotting 和 RT-PCR 结果表明，RtcB 可能通过 PAO1(∆∆)中的 RsmA 发挥其功能。c-di-GMP 的定量显示 PAO1(∆)中的细胞内水平升高，这可能导致 T6SS 和 T3SS 之间的转换，并导致观察到的表型和特征发生改变。我们的数据表明，RtcB 通过控制生物膜形成、运动性、绿脓菌素产生、T3SS 和 T6SS 分泌系统等多种毒力决定因素，在 毒力中发挥关键作用，针对真核细胞和原核细胞。这些发现表明 RtcB 是控制 定植、建立和致病性的潜在靶标。
