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Digitale Medien

QUORUM SENSING IN PLANT-PATHOGENIC BACTERIA (2003)

von Bodman, Susanne B. ; Bauer, W. Dietz ; Coplin, David L.

Palo Alto, Calif. : Annual Reviews

Annual Review of Phytopathology 41 (2003), S. 455-482

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ISSN: 0066-4286

Quelle: Annual Reviews Electronic Back Volume Collection 1932-2001ff

Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft , Biologie

Notizen: Quorum sensing (QS) allows bacteria to assess their local population density and/or physical confinement via the secretion and detection of small, diffusible signal molecules. This review describes how phytopathogenic bacteria have incorporated QS mechanisms into complex regulatory cascades that control genes for pathogenicity and colonization of host surfaces. Traits regulated by QS include the production of extracellular polysaccharides, degradative enzymes, antibiotics, siderophores, and pigments, as well as Hrp protein secretion, Ti plasmid transfer, motility, biofilm formation, and epiphytic fitness. Since QS regulatory systems are often required for pathogenesis, interference with QS signaling may offer a means of controlling bacterial diseases of plants. Several bacterial pathogens of plants that have been intensively studied and have revealed information of both fundamental and practical importance are reviewed here: Agrobacterium tumefaciens, Pantoea stewartii, Erwinia carotovora, Ralstonia solanacearum, Pseudomonas syringae, Pseudomonas aeruginosa, and Xanthomonas campestris.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1146/annurev.phyto.41.052002.095652

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Digitale Medien

The cell density-dependent expression of stewartan exopolysaccharide in Pantoea stewartii ssp. stewartii is a function of EsaR-mediated repression of the rcsA gene (2005)

Minogue, Timothy D. ; Carlier, Aurelien L. ; Koutsoudis, Maria D. ; [weitere]

Oxford, UK : Blackwell Science Ltd

Molecular microbiology 56 (2005), S. 0

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ISSN: 1365-2958

Quelle: Blackwell Publishing Journal Backfiles 1879-2005

Thema: Biologie , Medizin

Notizen: The LuxR-type quorum-sensing transcription factor EsaR functions as a repressor of exopolysaccharide (EPS) synthesis in the phytopathogenic bacterium Pantoea stewartii ssp. stewartii. The cell density-dependent expression of EPS is critical for Stewart's wilt disease development. Strains deficient in the synthesis of a diffusible acyl-homoserine lactone inducer remain repressed for EPS synthesis and are consequently avirulent. In contrast, disruption of the esaR gene leads to hypermucoidy and attenuated disease development. Ligand-free EsaR functions as a negative autoregulator of the esaR gene and responds to exogenous acyl-homoserine lactone for derepression. The focus of this study was to define the mechanism by which EsaR governs the expression of the cps locus, which encodes functions required for stewartan EPS synthesis and membrane translocation. Genetic and biochemical studies show that EsaR directly represses the transcription of the rcsA gene. RcsA encodes an essential coactivator for RcsA/RcsB-mediated transcriptional activation of cps genes. In vitro assays identify an EsaR DNA binding site within the rcsA promoter that is reasonably well conserved with the previously described esaR box. We also describe that RcsA positively controls its own expression. Interestingly, promoter proximal genes within the cps cluster are significantly more acyl-homoserine lactone responsive than genes located towards the middle or 3′ end of the gene cluster. We will discuss a possible role of EsaR-mediated quorum sensing in the differential expression of the cps operon.