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Title: Genetic and signal regulation of quorum sensing in Agrobacterium tumefaciens
Authors: WANG CHAO
Keywords: quorum quenching, semialdehyde acid, signal degradation, crown gall, stress response, ppGpp
Issue Date: 19-Dec-2007
Citation: WANG CHAO (2007-12-19). Genetic and signal regulation of quorum sensing in Agrobacterium tumefaciens. ScholarBank@NUS Repository.
Abstract: In Agrobacterium tumefaciens, a quorum sensing (QS) system modulates the Ti plasmid conjugation and replication and hence plays an important role in maintenance of the virulence genes in the bacterial population. Our lab has recently discovered a quorum quenching (QQ) system in this pathogen. This QQ mechanism consists of a transcriptional repressor AttJ and an AHL-lactonase AttM. Under normal conditions, QQ is not active. However, the AttM activity is strongly induced under environmental stresses, which leads to the degradation of QS signal and switching off QS. This project aimed to dissect the mechanism of QQ regulation. We demonstrated that this QQ system is activated by nutrient starvation via ppGpp. We showed succinic semialdehyde (SSA) is the signal ligand which couples the stress-response pathway to the QQ pathway. Genomics analysis revealed that SSA is able to promote nitrate and C4-dicarboxylate assimilation, enhance bacterial oxidative tolerance and biofilm production. Furthermore, we identified an additional TraM-like antiactivator doubly controls QS in some of the A. tumefaciens strains.
Appears in Collections:Ph.D Theses (Open)

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