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Chapter 6 : Regulatory Networks in Pathogenic Bacteria: Lessons from Cell-Cell Communication in Pseudomonas aeruginosa
Category: Bacterial Pathogenesis
Regulatory Networks in Pathogenic Bacteria: Lessons from Cell-Cell Communication in Pseudomonas aeruginosa, Page 1 of 2< Previous page | Next page > /docserver/preview/fulltext/10.1128/9781555815851/9781555814694_Chap06-1.gif /docserver/preview/fulltext/10.1128/9781555815851/9781555814694_Chap06-2.gif
Signal transduction and gene regulation show the steepest dependence on the total number of genes among all functional categories of genes in prokaryotic genomes, and this disproportionate increase in the hierarchical complexity of gene regulation with the increase in genome size may ultimately control the maximum achievable genome size. Vibrio cholerae and Pseudomonas aeruginosa are motile organisms with comparatively large genomes and complex regulatory systems reflecting their adaptability to diverse environments. Researchers have begun to decipher the underlying transcriptional networks and the role that these networks play in responding to a multitude of environmental conditions. The authors focus on one such regulatory network, quorum sensing, which allows P. aeruginosa to regulate hundreds of genes, many of which encode virulence factors, in response to population size. The genome-scale studies described in this chapter reveal that P. aeruginosa quorum sensing is a global regulatory system that affects many different cellular functions. The route of P. aeruginosa infection of course depends on the predisposing condition (for example, ventilator-associated pneumonia, burns, surgical wounds, and extended-wear contact lenses predispose to acute infection, whereas cystic fibrosis and implanted medical devices predispose to chronic infection) but also represents an important commitment by P. aeruginosa because acute and chronic routes of infection involve distinctly different virulence factors and bacterial lifestyles. P. aeruginosa quorum sensing is one of the best-understood cell-cell communication systems in bacteria.
Key Concept Ranking
- Type III Secretion System
Signaling complexity is related to genome size. Shown are the numbers of signaling systems (one- and two-component systems) corresponding to 150 sequenced genomes as a function of genome size (raw data were taken from reference 75 ). Black diamonds, pathogenic bacteria emphasized in the text.
Quorum-sensing circuitry. The schematic emphasizes the acyl-HSL signals, genes, and corresponding protein components of each quorum-sensing system. Circles denote acyl-HSL signals. Boxes upstream of target genes indicate conserved regulatory elements to which LasR, RhlR, or QscR bind. Some target (tgt) genes within the quorum-sensing regulon are activated by both LasR and RhlR.
Interconnection of quorum sensing with other regulatory networks. See the text for a detailed explanation. For enhanced clarity, effects on signal synthase and receptor expression have not been detailed separately. PA1760 is one of several predicted transcriptional regulators that is activated by las quorum sensing and appears to mediate quorum-sensing gene expression indirectly. The quorum-sensing regulon is defined as the collection of genes that is activated by LasR–3OC12-HSL or RhlR–C4-HSL, directly or indirectly. The different regulators shown affect the expression of overlapping subsets within the quorum-sensing (QS) regulon. ppGpp, guanosine tetraphosphate.