The Zur (zinc uptake regulator) regulon of a range of pathogenic and non-pathogenic E. coli strains was explored by combining in silico Zur binding site predictions with experimental approaches. Initially, novel Zur-binding sites were predicted in the genomes of K-12 MG1655, 0157:H7 str. Sakai, H10407 and CFT073 using patser. The effect of both zinc depletion and zur deletion was probed in each strain by transcriptomics analysis, in order to identify direct Zur targets. Known Zur targets, including zinT, an auxiliary component of the znuABC zinc uptake system, and ykgM, an alternative non-zinc-binding ribosomal protein were up-regulated in all strains under both zinc depletion and zur deletion conditions. In contrast, up-regulation of the high affinity zinc uptake system znuABC, was more modest and variable. Transcription of pUG (ycgK), encoding a periplasmic G-type lysozyme inhibitor, was up-regulated under zinc depletion conditions and upon zur deletion in all strains, and also possessed a high-scoring predicted Zur binding site within its promoter region, leading us to believe that it is a novel member of the conserved Zur regulon. Additionally, a novel Zurregulated operon, c1265-7 was predicted in the CFT073 genome, and validated by microarray data and the use of a promoter-lux fusion. C1265 appears to be a TonBdependent heme/hemoglobin receptor, whilst C1266 and C1267 showed significant homology to components of metal uptake systems. Deletion of c1265J 7, even in the presence of a znuABC deletion, showed no clear phenotypic outcome under a range of conditions tested. C1265-7 was found to be almost exclusively distributed in ExPEC strains suggesting it is of importance to extra-intestinal survival. Additionally, the severe growth defect of CFT073 D.zur, even in zinc-deplete media suggests the CFT073 zur regulon may include extra genes involved in zinc uptake. iii ... \ ...
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:606007 |
| Date | January 2012 |
| Creators | Clayton, Selina Ruth |
| Publisher | University of Nottingham |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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