Halle, Universiẗat, Diss., 2000.

Thesis (M.S.)--University of Wisconsin--Madison, 1969. / eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis--University of Wisconsin--Madison. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 116-121).

Thesis (M. Phil.)--University of Hong Kong, 2006. / Title proper from title frame. Also available in printed format.

The process of transformation has been demonstrated in Pseudomonas solanacearum. The DNA isolated from various virulent strains of the pathogen induced formation of wild-type virulent cells in pure cultures of weakly virulent strains of the organism. DNase completely inhibited the reaction. Cultures of transformed cells were found to be equally as pathogenic to tomato as the wild, virulent strains. The cells of both cultures were also shown to possess similar capacities for storing poly β-hydroxy butyric acid. Various comparative studies were carried out on virulent and weakly virulent strains of one of the isolates used in the transformation experiments. DMAs isolated from cells of the two strains were found to have identical G-C values, as determined by their buoyant densities in CsCl and their thermal denaturation temperatures. The organisms also manifested similar reactions in several biochemical tests commonly used in the identification of bacterial species. Antisera were prepared against the cells and extracellular products of both strains. Serological studies indicated the presence of common antigenic determinants among the four different antigens. However, evidence was produced which suggested some heterogeneity of antigenic components. Chromatographic analyses of the extracellular products of the two strains indicated no qualitative differences in the sugar or amino acid components. Glucose, fructose, galactosamine and mannose were the sugars detected, while the amino acid components included leucine, phenylalanine, methionine, lysine, glycine, glutamic acid, alanine, hydroxyproline and an unidentified amino acid. The latter moved at the same rate as histidine but gave a different colour with ninhydrin spray. An argument attempting to coordinate results of the two phases of the study was presented. Further, the significance of the phenomenon of transformation in the biology of Pseudomonas solanacearum was briefly discussed. / Land and Food Systems, Faculty of / Graduate

published_or_final_version / abstract / Botany / Master / Master of Philosophy

published_or_final_version / Biological Sciences / Master / Master of Philosophy

published_or_final_version / Biological Sciences / Master / Master of Philosophy

Burkholderia sp. MBA4 was identified from soil for its ability to grow on monobromoacetic acid. A dehalogenase, Deh4a, confers a dehalogenation function in MBA4. A permease gene, deh4p, forms a haloacid operon with deh4a. Deh4a has been well characterized but the regulatory mechanism of the haloacid operon was unknown. Electrophoretic mobility shift assay shows that at least one regulatory protein exists and binds with the promoter of deh4a. A DNA-affinity column purified several DNA-binding proteins and two proteins were identified by tandem mass spectroscopy as putative transcriptional regulators of B. xenovorans LB400. One of these proteins was named IclR1 and subjected to further analysis in this study. Here I report the cloning of the iclR1 gene and the functional study of this protein. The iclR1 gene was cloned by means of chromosome walking. The iclR1 gene has 837 bases and encodes 278 amino acids. The putative protein is classified as a member of the IclR family. Recombinant IclR1 was produced in E. coli and purified by Ni-NTA column. The experimental size of IclR1 is 27.5 kD and a dimer of 52.3 kD can be identified in vitro with cross-linking reagent. Purified IclR1 failed to bind the deh4a promoter, and mutants with a disrupted iclR1 gene or over-expressing IclR1 has no effect on the deh4a expression. It is likely that IclR1 is not a regulator of the haloacid operon. EMSA shows that IclR1 binds to its own promoter which contains a palindrome sequence and a pair of inverted repeats upstream of the start codon. The transcription start site of iclR1 was determined to be a G 110 bp upstream of the start codon by 5’ RACE. The iclR1 promoter region was ligated with a lacZ reporter gene, and transformed into wild type MBA4, a disruptant and an over-producer mutant. ONPG assay shows that the expression of the reporter is induced by NaCl. The transcript level of iclR1 is also higher in NaCl-containing medium. Over-expression of IclR1 inhibits the expression of the reporter, indicating that IclR1 is a self-regulated repressor. The growth of an iclR1 disruptant is more sensitive to salt. These results suggest that IclR1 is beneficial for the survival of the cell in NaCl stress, but excessive IclR1 prevent the responding system from overworking. Since MBA4 is very sensitive to NaCl, understanding the NaCl-related physiology of MBA4 is important. The gene(s) under direct control of IclR1 is unknown and the specific function of IclR1 awaits further study. / published_or_final_version / Biological Sciences / Doctoral / Doctor of Philosophy

Thesis (M. Phil.)--University of Hong Kong, 2009. / Includes bibliographical references (leaves 112-131) Also available in print.