| Author | Worawan Kitphati |
| Call Number | AIT Diss. no.EV-08-10 |
| Subject(s) | Agrobacterium tumefaciens
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| Note | A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Environmental Engineering and Management Inter-University Program on Environmen tal Toxicology, Technology and Management |
| Publisher | Asian Institute of Technology |
| Series Statement | Dissertation ; no. EV-08-10 |
| Abstract | Iron is an essential metal for bacterial survival due to the fact that it is a required cofactor in a large number of iron-containing enzymes and proteins. However, when present in excess it can be toxic due to its ability to induce the generation of highly deleterious free radicals via the Fenton reaction. Therefore, intracellular iron concentrations need to be carefully adjusted by controlling iron transport, storage and consumption. In many bacteria, this regulation is mediated by the ferric uptake regulator (Fur) protein. Fur is a 17 KDa DNA binding protein which represses the transcription of many iron-responsive genes in Escherichia coli and other bacteria. Fur regulates not only iron-regulated genes but also genes involved in; metal homeostasis, the oxidative stress response and virulence. Agrobacterium tumefaciens is a soil-born plant pathogen that causes crown gall tumor in many dicotyledonous plants. The A. tumefaciens genome encodes 3 fur homologues; fur, irr and zur. In order to determine the functional role of A.tumefaciens Fur, an A. tumefaciens fur mutant was constructed by insertional inactivation. The mutant construction was confirmed by Southern blot analysis. The phenotypes of this mutant relating to metal homeostasis and the oxidative stress response were investigated. Atypically, A.tumefaciens Fur did show alterations in the levels of siderophore biosynthesis. However, the A. tumefaciens fur mutant was more sensitive to an iron chelator, 2,2-dipyridyl, and more resistant to an iron-activated antibiotic, streptonigrin, than the wild type A. tumefaciens NTLâ‚„. This suggested that Fur has a role in regulating the intracellular iron concentration and that the A. tumefaciens fur mutant was iron-deficient. Apart from iron, A.tumefaciens Fur may also be involved in the regulation of divalent cation homeostasis. A. tumefaciens Fur was shown to playa role in the oxidative stress response. The A. tumefaciens fur mutant was hypersensitive to hydrogen peroxide and showed reduced catalase activity. Virulence assays showed that the A. tumefaciens fur mutant had a reduced ability to cause tumors on tobacco leaves compared to the wild type strain. The virulence deficiency of the A. tumefaciens fur mutant was proposed to be due, at least in part, to an impaired ability to cope with oxidative stress conditions caused primarily by a reduction in catalase levels |
| Year | 2008 |
| Corresponding Series Added Entry | Asian Institute of Technology. Dissertation ; no. EV-08-10 |
| Type | Dissertation |
| School | School of Environment, Resources, and Development (SERD) |
| Department | Department of Energy and Climate Change (Former title: Department of Energy, Environment, and Climate Change (DEECC)) |
| Academic Program/FoS | Environmental Engineering and Management (EV) |
| Chairperson(s) | Skorn Mongkolsuk ;Preeda Parkpian (Co-Chairperson) |
| Examination Committee(s) | Suvit Loprasert ;Dubbs, James M. |
| Scholarship Donor(s) | Chulabhorn Research Institute ;Mahidol University ;Asian Institute of Technology Fellowship ;Office of Higher Education Commission (OHEC), Thailand |
| Degree | Thesis (Ph.D.) - Asian Institute of Technology - Chulabhorn Research Institute - Mahidol University, 2008 |