Quorum sensing: Dynamic response of Pseudomonas aeruginosa to external signals

Department of Microbiology and Immunology, University of Rochester, Rochester, NY 14642, USA.
Trends in Microbiology (Impact Factor: 9.19). 03/2006; 14(2):55-8. DOI: 10.1016/j.tim.2005.12.002
Source: PubMed


A recent study suggests that the opportunistic pathogen Pseudomonas aeruginosa can actively monitor the host immune system. The P. aeruginosa outer membrane protein OprF was found to bind specifically to the cytokine interferon-gamma (IFN-gamma), and this interaction upregulated production of virulence factors through a cell-cell communication system known as quorum sensing (QS). Taken together with previous findings that P. aeruginosa QS can alter the host immune response (e.g. by activation of IFN-gamma), these data illustrate an exciting new element of bacteria-host interactions in which the P. aeruginosa quorum-sensing system both senses and modulates the host immune state.

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Available from: Victoria E Wagner, Feb 11, 2015
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    • "Thealternativeoradditionalpossibilitythattheeffectscaused bytheabsenceofOprFresultfromsomethingelseotherthanOM disorganizationcannotbedisregarded,especiallyconsidering theroleofOprFasahostimmunesystemsensor(Wuetal., 2005;Mishraetal.,2015),moregenerallyasanenvironmental sensor(Wagneretal.,2006;Fito-Boncompteetal.,2011).It isalsoconceivablethatOprF-dependentc-di-GMPmodulation islinkedtoitsabilitytotransmitortotransduceunknown signalsthroughtheOM,whichwouldthenbedetectedbya sensorproteininthecytoplasmicmembrane.Takentogether,our datashowforthefirsttimethatOprFislinkedtoc-di-GMP levelmodulations,throughadirect(signaling)and/orindirect (envelopestress)mechanism. "
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    ABSTRACT: OprF is the major outer membrane porin in bacteria belonging to the Pseudomonas genus. In previous studies, we have shown that OprF is required for full virulence expression of the opportunistic pathogen Pseudomonas aeruginosa. Here, we describe molecular insights on the nature of this relationship and report that the absence of OprF leads to increased biofilm formation and production of the Pel exopolysaccharide. Accordingly, the level of c-di-GMP, a key second messenger in biofilm control, is elevated in an oprF mutant. By decreasing c-di-GMP levels in this mutant, both biofilm formation and pel gene expression phenotypes were restored to wild-type levels. We further investigated the impact on two small RNAs, which are associated with the biofilm lifestyle, and found that expression of rsmZ but not of rsmY was increased in the oprF mutant and this occurs in a c-di-GMP-dependent manner. Finally, the extracytoplasmic function (ECF) sigma factors AlgU and SigX displayed higher activity levels in the oprF mutant. Two genes of the SigX regulon involved in c-di-GMP metabolism, PA1181 and adcA (PA4843), were up-regulated in the oprF mutant, partly explaining the increased c-di-GMP level. We hypothesized that the absence of OprF leads to a cell envelope stress that activates SigX and results in a c-di-GMP elevated level due to higher expression of adcA and PA1181. The c-di-GMP level can in turn stimulate Pel synthesis via increased rsmZ sRNA levels and pel mRNA, thus affecting Pel-dependent phenotypes such as cell aggregation and biofilm formation. This work highlights the connection between OprF and c-di-GMP regulatory networks, likely via SigX (ECF), on the regulation of biofilm phenotypes.
    Full-text · Article · Jun 2015 · Frontiers in Microbiology
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    • "So far, the majority of studies on the role of AHLs have been based on genetic approaches (De Kievit et al., 2001; Pesci, Pearson, Seed, & Iglewski, 1997; Venturi, 2006) in which AHL synthase knock-out mutants were used to evaluate the potential phenotypes regulated by the signaling compounds (Whiteley et al., 1999). AHL-producing microorganisms are able to synthesize AHLs when they reach a sufficiently high population density (Medina-Martínez, Uyttendaele, Demolder, & Debevere, 2006; Pesci et al., 1997; Venturi, 2006; Zhang et al., 2013), and for many AHL QS-regulated genes, a quorum concentration of AHL signal molecules is necessary (Diggle, Winzer, Lazdunski, Williams, & Cámara, 2002; Schuster, Lostroh, Ogi, & Greenberg, 2003; Wagner et al., 2006). However, it is not well understood what happens when low numbers of microorganisms, that perhaps themselves do not produce AHLs, encounter AHLs in the environment. "
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    ABSTRACT: The objective of this study was to examine the effect of an acylated homoserine lactones-containing culture extract (AHL-CCE) on bacterial growth, enzyme activity and biofilm formation of Pseudomonas aeruginosa. Chicken breast muscle broth in which P. aeruginosa had been grown for 24 h at 20 °C was extracted with acidified ethyl acetate, the solvent was evaporated and the residue was dissolved in water and heated at 100 °C for 15 min. Thin-layer chromatography combined with Agrobacterium tumefaciens KYC55-based bioassays indicated the presence of C4-, C6-, C8- and C12-homoserine lactones in the extract. The addition of AHL-CCE to a culture of P. aeruginosa caused the bacteria to reach their highest count after 36 h whereas cultures without the extract required 72 h to reach their peak counts, but the maximum cell count was higher for the extract-free culture. No biofilm was detected when P. aeruginosa was cultured in chicken broth at 10 °C when the extract was present. Addition of extract reduced proteolysis of actin, troponin-T and tropomyosin by P. aeruginosa, but had no effect on lipase activity. Therefore, AHL-CCE can be used to reduce the bacterial growth time and inhibit biofilm formation; thus, benefiting food safety and quality.
    Full-text · Article · Jun 2014 · Lebensmittel-Wissenschaft und-Technologie
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    • "Thus, these characteristics do not exist in many single cells, such as commensalism, bioluminescence, thallus motility, antibiotic synthesis, plasmid conjugate transfer, animal/plant pathogenesis, toxic factor expression, and biomembrane/spore formation [3] [4] . This important mechanism for synchronous gene expression and functional coordination of bacterial colony may prevent and treat pathogen by interfering QS signal molecule [5] [6] . The synthesis and degradation of QS signal molecule can be regulated through modern biotechnological means. "
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    ABSTRACT: An associated heterotrophic dominant single bacteria-Z-QS01 was selected to study its mechanism of quorum sensing and factors that affected quorum sensing by using ecotoxicological method in co-cultural system with Chlorella vulgaris. The results showed that self-regulation and inhibitive effect to Chlorella vulgaris of bacteria-Z-QS01 were conducted through excreting chemic substance. Density of bacteria-Z-QS01 and concentration of chemic substance excreted by bacteria-Z-QS01 were necessary conditions, which decided whether the regulation mechanism could be carried out or not; enhanced UV-B radiation could affect quorum sensing of bacteria-Z-QS01 significantly, and the inhibitition effect was enhanced gradually with the dose of UV-B radiation increasing.
    Full-text · Article · Dec 2011
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