Novel roles for two-component regulatory systems in cytotoxicity and virulence-related <em>properties in Pseudomonas aeruginosa</em>

Abstract

The rapid adaptation of the opportunistic bacterial pathogen Pseudomonas aeruginosa to various growth modes and environmental conditions is controlled in part through diverse two-component regulatory systems. Some of these systems are well studied, but the majority are poorly characterized, even though it is likely that several of these systems contribute to virulence. Here, we screened all available strain PA14 mutants in 50 sensor kinases, 50 response regulators and 5 hybrid sensor/regulators, for contributions to cytotoxicity against cultured human bronchial epithelial cells, as assessed by the release of cytosolic lactate dehydrogenase. This enabled the identification of 8 response regulators and 3 sensor kinases that caused substantial decreases in cytotoxicity, and 5 response regulators and 8 sensor kinases that significantly increased cytotoxicity by 15–58% or more. These regulators were additionally involved in motility, adherence, type 3 secretion, production of cytotoxins, and the development of biofilms. Here we investigated in more detail the roles of FleSR, PilSR and WspR. Not all cognate pairs contributed to cytotoxicity (e.g. PhoPQ, PilSR) in the same way and some differences could be detected between the same mutants in PAO1 and PA14 strain backgrounds (e.g. FleSR, PhoPQ). This study highlights the potential importance of these regulators and their downstream targets on pathogenesis and demonstrates that cytotoxicity can be regulated by several systems and that their contributions are partly dependent on strain background.

Pseudomonas aeruginosa biofilm formation on endotracheal tubes requires multiple two-component systems

“…We noted certain similarities between TCS genes involved in the biofilm formation on ETTs (this study) and those reported for biofilm formation on other surfaces such as polystyrene and glass [40,72,73]. This included the regulator of flagellum biogenesis FleR-FleS, phosphate response regulator PhoQ, and AlgR-KinB (Fig.…”

“…These studies have reported many TCS mutants with increased biofilm biomass. Of these negative regulators previously reported, we found that mutants in 22 genes, pilG, creB, creC, agtR, hsbR, hptB, PA3271, sagS, czcR, parR, PA14_43670 (PA1611), PA14_46370 (PA1396), PA14_52250 (PA0929), gacS, rcsB, cbrA, PA14_63210 (PA4781), gcbA, ntrB, dctB, algZ and algB had increased biofilm biomass on ETT surface [16,40,73,79,92,94,98,99,[101][102][103][104]. In addition, we found six new genes, agtS, cprR, parS, pprA, colR and pmrB with increased biofilm biomass.…”

“…Although a systematic analysis of the requirement of all TCS genes in biofilm formation has not been attempted in a single study, several studies have looked at the role of many TCS components in biofilm formation. The majority of these studies were done in microtitre plates (polystyrene material), and some on PVC surface or glass surface [11,16,25,40,73,[92][93][94][95][96][97][98][99][100]. These studies have reported many TCS mutants with increased biofilm biomass.…”

“…Of the 28 TCSs needed for the formation of biofilm on ETTs, FleR, FleS, PhoQ, AlgR and KinB have been reported to be involved in biofilm formation on other surfaces previously [34,46,72,93]. The loss of wspR (PA3702) enhanced the biofilm formation in polystyrene plates [40,73], but not on ETTs. This finding suggests that WspR chemosensory system may have a function in sensing harder surfaces such as polystyrene.…”

NtrBC Regulates Invasiveness and Virulence of Pseudomonas aeruginosa During High-Density Infection

“…Phenotypic screening of transposon mutants revealed that NtrC contributes to swarming motility (Yeung et al, 2009). Furthermore, we previously showed that mutants in ntrB and ntrC demonstrated modestly (∼20%) increased toxicity and substantially reduced adherence to epithelial cells (Gellatly et al, 2018). Here, the pathogenic properties of NtrB and NtrC were further explored.…”