04571nas a2200433 a 4500 20260818171903.0 090602s2008 th uu|m rtt 0| a1eng d .b12057381 AIT Diss. no.EV-08-10 Worawan Kitphati Physiological study of Ferric Uptake Regulator (FUR) gene in agrobacterium tumefaciens Pathum Thani, Thailand : Asian Institute of Technology, 2008 136 p. : ill. Dissertation ; no. EV-08-10 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 Thesis (Ph.D.) - Asian Institute of Technology - Chulabhorn Research Institute - Mahidol University, 2008 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 NTL₄. 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 Agrobacterium tumefaciens Skorn Mongkolsuk, Chairperson Preeda Pakpian, Examination Committee Suvit Loprasert, Examination committee Dubbs, James M., Examination committee Chulabhorn Research Institute, Scholarship donor Mahidol University, Scholarship donor Asian Institute of Technology Fellowship, Scholarship donor Office of Higher Education Commission (OHEC), Thailand, Scholarship donor Asian Institute of Technology. Dissertation ; no. EV-08-10 Full-Text http://203.159.5.9/ait-thesis/detail.php?q=B00534 .b12057381 mnait u 240329 0 090602 m a u 0 mnait mnarc 22 40 Barcode : 30050120725709 CREATED : 2012-08-16 RECORD # : i12687261 LPATRON : 0 LCHKIN : - # RENEWALS : 0 # OVERDUE : 0 IUSE3 : 0 TOT CHKOUT : 0 TOT RENEW : 0 Barcode : 30050160004270 CREATED : 2016-09-02 RECORD # : i1287890x LPATRON : 0 LCHKIN : - # RENEWALS : 0 # OVERDUE : 0 IUSE3 : 0 TOT CHKOUT : 0 TOT RENEW : 0 87894 87894 0 0 0 0 MAIN MAIN mnait 2026-08-18 0 AIT Diss. no.EV-08-10 30050120725709 2026-08-18 17:19:03 3 2026-08-18 22 0 0 0 0 MAIN MAIN mnarc 2026-08-18 0 AIT Diss. no.EV-08-10 30050160004270 2026-08-18 17:19:03 2026-08-18 40