Article

Pseudomonas aeruginosa AlgR represses the Rhl quorum-sensing system in a biofilm-specific manner.

Tulane University Health Sciences Center, Department of Microbiology and Immunology, New Orleans, LA 70112, USA.
Journal of Bacteriology (Impact Factor: 2.69). 12/2007; 189(21):7752-64. DOI: 10.1128/JB.01797-06
Source: PubMed

ABSTRACT AlgR controls numerous virulence factors in Pseudomonas aeruginosa, including alginate, hydrogen cyanide production, and type IV pilus-mediated twitching motility. In this study, the role of AlgR in biofilms was examined in continuous-flow and static biofilm assays. Strain PSL317 (DeltaalgR) produced one-third the biofilm biomass of wild-type strain PAO1. Complementation with algR, but not fimTU-pilVWXY1Y2E, restored PSL317 to the wild-type biofilm phenotype. Comparisons of the transcriptional profiles of biofilm-grown PAO1 and PSL317 revealed that a number of quorum-sensing genes were upregulated in the algR deletion strain. Measurement of rhlA::lacZ and rhlI::lacZ promoter fusions confirmed the transcriptional profiling data when PSL317 was grown as a biofilm, but not planktonically. Increased amounts of rhamnolipids and N-butyryl homoserine lactone were detected in the biofilm effluent but not the planktonic supernatants of the algR mutant. Additionally, AlgR specifically bound to the rhlA and rhlI promoters in mobility shift assays. Moreover, PAO1 containing a chromosomal mutated AlgR binding site in its rhlI promoter formed biofilms and produced increased amounts of rhamnolipids similarly to the algR deletion strain. These observations indicate that AlgR specifically represses the Rhl quorum-sensing system during biofilm growth and that such repression is necessary for normal biofilm development. These data also suggest that AlgR may control transcription in a contact-dependent or biofilm-specific manner.

0 Bookmarks
 · 
142 Views
  • [Show abstract] [Hide abstract]
    ABSTRACT: Pseudomonas aeruginosa virulence components are subject to complex regulatory control primarily through two-component regulatory systems that allow for sensing and responding to environmental stimuli. In this study, the expression and regulation of the P. aeruginosa AlgZR two-component regulatory system were examined. Primer extension and S1 nuclease protection assays were used to identify two transcriptional initiation sites for algR within the algZ coding region, and two additional start sites were identified upstream of the algZ coding region. The two algR transcriptional start sites, RT1 and RT2, are directly regulated by AlgU consistent with previous reports of increased algR expression in mucoid backgrounds, and RpoS additionally plays a role in algR transcription. The expression of the first algZ promoter, ZT1, is entirely dependent upon Vfr for expression whereas Vfr, RpoS or AlgU does not regulate the second algZ promoter, ZT2. Western blot, RT-qPCR and transcriptional fusion analyses show that algZR expression is Vfr-dependent. The algZ and algR genes are also co-transcribed, in both nonmucoid and mucoid backgrounds. Furthermore, algZR was found to be co-transcribed with hemCD by RT-PCR. RT-qPCR confirmed that hemC transcription in PAO1 ΔalgZ was 40% of the wild-type strain. Taken together these results indicate that algZR transcription involves multiple factors at multiple start sites that control individual gene expression as well as co-expression of this two-component system with heme biosynthetic genes. Copyright © 2014, American Society for Microbiology. All Rights Reserved.
    Journal of Bacteriology 12/2014; 197(4). DOI:10.1128/JB.02290-14 · 2.69 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: In the recent years, biosurfactants proved to be an interesting alternative to petrochemically derived surfactants. Two classes of biosurfactants, namely glycolipids and lipopeptides, have attracted significant commercial interest. Despite their environmental advantages and equal performance, commercialization of these molecules remains a challenge due to missing acquaintance of the applicants, higher price and lack of structural variation. The latter two issues can partially be tackled by screening for novel and better wild-type producers and optimizing the fermentation process. Yet, these traditional approaches cannot overcome all hurdles. In this review, an overview is given on how biotechnology offers opportunities for increased biosurfactant production and the creation of new types of molecules, in this way enhancing their commercial potential.
    Current Opinion in Biotechnology 07/2014; 30C:66-72. DOI:10.1016/j.copbio.2014.06.002 · 8.04 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Pseudomonas aeruginosa is an opportunistic pathogen that causes a multitude of infections. These infections can occur at almost any site in the body and are usually associated with a breach of the innate immune system. One of the prominent sites where P. aeruginosa causes chronic infections is within the lungs of cystic fibrosis patients. P. aeruginosa uses two-component systems that sense environmental changes to differentially express virulence factors that cause both acute and chronic infections. The P. aeruginosa AlgZR two component system is one of its global regulatory systems that affects the organism's fitness in a broad manner. This two-component system is absolutely required for two P. aeruginosa phenotypes: twitching motility and alginate production, indicating its importance in both chronic and acute infections. Additionally, global transcriptome analyses indicate that it regulates the expression of many different genes, including those associated with quorum sensing, type IV pili, type III secretion system, anaerobic metabolism, cyanide and rhamnolipid production. This review examines the complex AlgZR regulatory network, what is known about the structure and function of each protein, and how it relates to the organism's ability to cause infections.
    Frontiers in Cellular and Infection Microbiology 06/2014; 4:82. DOI:10.3389/fcimb.2014.00082 · 2.62 Impact Factor

Full-text (2 Sources)

Download
36 Downloads
Available from
May 17, 2014