Bibliography: leaves 165-188. This research examines biological and behavioural interactions among the diamond-back moth, Plutella xylostella L. (Lepidoptera: Plutellidae), Cotesia plutellae Kurdjumov (Hymenoptera: Braconidae) and the microbial insecticide, Bacillus thuringiensis Berliner. A deterministic simulation model is developed describing the influence of C. plutellae on the evolution of resistance to Bt in a diamond-back moth poulation.

Graduation date: 1995

Bacillus thuringiensis NEB17 is a plant growth promoting rhizobacterium that produces a compound that directly increases plant growth. The compound is a bacteriocin and we propose the name thuricin 17. Thuricin 17 is a novel peptide inhibiting the growth of Bacillus species/strains, displaying both bactericidal and static effects. Its molecular weight, estimated via SDS-PAGE and verified by MALDI-QTOF mass spectroscopy, is 3162 Da. The partial amino acid sequence was determined and is N-term---WTCWSCLVCAACSVELL, C-term-CAS. Heat and pH stability, production and susceptibility to proteolysis were conducted. Thuricin 17 is active in pH 1.00-9.25, stable above 60°C and produced in the late exponential growth phase. This is the first bacteriocin from a Bacillus PGPR and the first reported to increase plant growth. This work presents an original discovery regarding PGPR mechanisms.

Methylobacterium extorquens ATCC55366 is an interesting candidate for large-scale production of recombinant proteins. Development and optimization of this recombinant expression system were done using the green fluorescent protein (GFP) gene cloned into expression vectors (pRK310 and pCM110) as model systems. Selection of efficient GFP-expressing clones, long-term production stability without selection in flasks, effects of selection, oxygen and methanol supplies, were studied during fed-batch fermentations in a 20-l bioreactor. Sequential batch-culture cultivations in shake flasks showed that specific GFP production was constant in the presence of tetracycline. However, the GFP production decreased in the absence of this selective pressure. In fed-batch fermentations of recombinant M. extorquens ATCC 55366 (pMxaF-GFP), overall GFP yields (≈70 mg/g; GFP/cell dry weight) were not affected by the presence or absence of tetracycline, nor by oxygen and methanol concentration oscillations. The cry1Aa gene from Bacillus thuringiensis kurstaki NRD-12 was cloned in pCM110 and then transformed into M. extorquens. Heterologous expression of the cry1Aa gene in M. extorquens AM1 and ATCC 55366 was detected by immunoblot analyses. This study suggests that M. extorquens can be used as a valuable expression system for intracellular recombinant protein production.

The purpose of this study was to compare the pathology caused by two bacterial species, Bacillus subtilis and Bacillus thuringiensis, in European corn borer larvae. The study consisted of: (1) a determination of the mortality of larvae that had ingested various concentrations of bacterial spores; (2) light microscopic examination of midgut tissues of larvae treated with various concentrations of bacterial spores, and (3) examination of midgut tissues of treated larvae with transmission electron microscopy.The results of the mortality study indicated that B. subtilis did not cause mortality in corn borer larvae. Light and electron microscopy did not reveal any pathological damage to midgut tissues of larvae treated with B. subtilis. It was observed that there was an increase in the amount of peritrophic membrane produced in the larvae treated with B. subtilis. These larvae were also observed to be sluggish and have diahrrea, suggesting a mild disease state.Mortality in larvae treated with B. thuringiensis varied with the concentration of spores ingested, and ranged as high as 100 percent. The mortality data were used to select three spore concentrations, corresponding to 25 percent, 50 percent, and 90 percent mortality levels. Larvae treated with B. thuringiensis spores in these concentrations were then examined by light microscopy. The pathology observed included slight swelling and vacuolation of the epithelial cells, cellular disruption, and complete breakdown of the epithelial tissue and subsequent bacteremia. It was observed that the degree of pathology increased with an increase in the bacterial spore concentration.Electron microscopic examination of midgut of B. thuringiensis treated larvae revealed the following pathological symptoms: decrease in apical microvilli, decrease in microvilli of goblet cells, and decrease in basal infoldings of plasma membrane.

Bibliography: leaves 165-188. / ix, 188 leaves, [2] leaves of plates : ill. (some col.) ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / This research examines biological and behavioural interactions among the diamond-back moth, Plutella xylostella L. (Lepidoptera: Plutellidae), Cotesia plutellae Kurdjumov (Hymenoptera: Braconidae) and the microbial insecticide, Bacillus thuringiensis Berliner. A deterministic simulation model is developed describing the influence of C. plutellae on the evolution of resistance to Bt in a diamond-back moth poulation. / Thesis (Ph.D.)--University of Adelaide, Dept. of Crop Protection, 1998

Thesis (Ph. D.)--University of Adelaide, Dept. of Crop Protection, 1998. / Includes bibliographical references (leaves 165-188).

Thesis (Ph. D.)--Auburn University. / Abstract. Includes bibliographical references.

Thesis (Ph. D.)--West Virginia University, 1999. / Title from document title page. Document formatted into pages; contains x, 149 p. : ill. Vita. Includes abstract. Includes bibliographical references (p. 138-142).

Hohenheim, Univ., Diss., 2004.