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Category: Bacterial Pathogenesis
Quorum Sensing in Burkholderia, Page 1 of 2
< Previous page | Next page > /docserver/preview/fulltext/10.1128/9781555818524/9781555816766_Chap03-1.gif /docserver/preview/fulltext/10.1128/9781555818524/9781555816766_Chap03-2.gifAbstract:
This chapter focuses on quorum sensing in Burkholderia, specifically Burkholderia pseudomallei, Burkholderia thailandensis, and Burkholderia mallei (the Bptm group). This group has highly conserved quorum sensing systems, yet each species occupies strikingly different environments. Quorum sensing systems have been found in all of the Burkholderia species studied to date. Prior to discussing the quorum sensing components of the Bptm group, it is important to understand the evolutionary history and lifestyle of each species. B. thailandensis and B. pseudomallei are saprophytic bacteria found in the soil and water in tropical regions common to Southeast Asia, northern Australia, South America, the Middle East, and some regions in Africa. Diagnosis and treatment of melioidosis are challenging because the disease presents with various symptoms and B. pseudomallei is intrinsically multidrug-resistant. Quorum sensing was first described to occur in the Bptm group within the past decade. The quorum sensing circuits in these bacteria are among the most complex acylated homoserine lactone (AHL) systems described. A summary of the quorum sensing components and AHL signals for each species is discussed in the chapter. Quorum sensing in B. pseudomallei has many parallels with quorum sensing in P. aeruginosa. Bacterial adherence, aggregation into microcolonies, and biofilm formation are important survival factors during the saprophytic and host-associated lifestyle of many opportunistic pathogens. The quorum sensing-controlled phenotypes observed in B. thailandensis are consistent with the idea that this bacterium uses quorum sensing during its saprophytic lifestyle.
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Some examples of AHL quorum sensing signals. The AHL structures and corresponding names are shown, organized by chain length or complexity. The signal made by RhII of P. aeruginosa is C4-HSL. LuxI of V. fisheri makes 3OC6-HSL. The Bptm signals of QS-1, QS-2, and QS-3 are C8-HSL, 3OHC10-HSL, and 3OHC8-HSL, respectively. LasI of P. aeruginosa produces 3OC12- HSL, and RpaI of R. palustris synthesizes para-coumaroyl-HSL (pC-HSL). doi:10.1128/9781555818524.ch3f1
Some examples of AHL quorum sensing signals. The AHL structures and corresponding names are shown, organized by chain length or complexity. The signal made by RhII of P. aeruginosa is C4-HSL. LuxI of V. fisheri makes 3OC6-HSL. The Bptm signals of QS-1, QS-2, and QS-3 are C8-HSL, 3OHC10-HSL, and 3OHC8-HSL, respectively. LasI of P. aeruginosa produces 3OC12- HSL, and RpaI of R. palustris synthesizes para-coumaroyl-HSL (pC-HSL). doi:10.1128/9781555818524.ch3f1
AHL signaling in V. fischeri (A) and P. aeruginosa (B). AHL signals (see Fig. 1 ) are made by members of the LuxI family of signal synthases and specifically interact with LuxR family transcription factors. At high cell density, AHLs accumulate and interact with LuxR homologs. AHL interaction causes the LuxR protein to change conformation and become active, which induces target gene regulation. (A) In V. fischeri, LuxI and LuxR produce and respond to 3OC6-HSL (red stars), respectively. (B) In P. aeruginosa, the LasIR system produces and responds to 3OC12-HSL (purple stars), and the RhlR system produces and responds to C4-HSL (green stars). QscR is an orphan LuxR receptor that is not genetically linked to a luxI synthase gene. QscR responds to 3OC12-HSL produced by LasI. Each quorum sensing regulon is shown as a distinct entity in the figure, but in reality there exists some overlapping regulation among the controlled genes. doi:10.1128/9781555818524.ch3f2
AHL signaling in V. fischeri (A) and P. aeruginosa (B). AHL signals (see Fig. 1 ) are made by members of the LuxI family of signal synthases and specifically interact with LuxR family transcription factors. At high cell density, AHLs accumulate and interact with LuxR homologs. AHL interaction causes the LuxR protein to change conformation and become active, which induces target gene regulation. (A) In V. fischeri, LuxI and LuxR produce and respond to 3OC6-HSL (red stars), respectively. (B) In P. aeruginosa, the LasIR system produces and responds to 3OC12-HSL (purple stars), and the RhlR system produces and responds to C4-HSL (green stars). QscR is an orphan LuxR receptor that is not genetically linked to a luxI synthase gene. QscR responds to 3OC12-HSL produced by LasI. Each quorum sensing regulon is shown as a distinct entity in the figure, but in reality there exists some overlapping regulation among the controlled genes. doi:10.1128/9781555818524.ch3f2
Quorum sensing circuits of B. thailandensis, B. pseudomallei, and B. mallei. Shown are the genetic context of the homologous quorum sensing circuits (QS-1, QS-2, and QS-3) in B. thailandensis (Bt), B. pseudomallei (Bp), and B. mallei (Bm). The cognate signal of each system is shown below the QS designation, and each structure can be found in Fig. 1 . The signals that bind the orphan LuxR homologs have not been determined (nd). The genes for the QS-1 LuxIR homologs are separated by a small region that contains one or two open reading frames of unknown function. The genes coding for the QS-2 LuxIR homologs are found within the bactobolin biosynthetic gene cluster and are separated by three open reading frames predicted to contribute to bactobolin synthesis. The genes coding for the LuxIR homologs of the QS-3 system are separated by a small intergenic region that does not contain additional open reading frames. doi:10.1128/9781555818524.ch3f3
Quorum sensing circuits of B. thailandensis, B. pseudomallei, and B. mallei. Shown are the genetic context of the homologous quorum sensing circuits (QS-1, QS-2, and QS-3) in B. thailandensis (Bt), B. pseudomallei (Bp), and B. mallei (Bm). The cognate signal of each system is shown below the QS designation, and each structure can be found in Fig. 1 . The signals that bind the orphan LuxR homologs have not been determined (nd). The genes for the QS-1 LuxIR homologs are separated by a small region that contains one or two open reading frames of unknown function. The genes coding for the QS-2 LuxIR homologs are found within the bactobolin biosynthetic gene cluster and are separated by three open reading frames predicted to contribute to bactobolin synthesis. The genes coding for the LuxIR homologs of the QS-3 system are separated by a small intergenic region that does not contain additional open reading frames. doi:10.1128/9781555818524.ch3f3
Some AHL quorum sensing-regulated processes in diverse Proteobacteria
Some AHL quorum sensing-regulated processes in diverse Proteobacteria