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1	Investigation of approaches to assess the consequences of introduction of a genetically modified bacterial inoculum to soil Povey, Jill Denise January 1994 (has links) This study was carried out as part of a contract funded by the Scottish Office to determine whether approaches to risk assessment, based on current recommendations, were adequate in determining the possibility of an adverse environmental effect of introduction of GMOs to the environment. The studies used a representative soil bacterium, Pseudomonas fluorescens, genetically modified by either chromosomal (FAC510) or plasmid (pUCD607) insertion of lux genes for bioluminescence. The starvation state is considered an important stress factor that bacteria added to soil may face. The ability to recover from this state, when substrates and nutrients become available, may be considered essential for the success of an introduced organism, and may ultimately determine the ecological effects of a GMO. The recovery response to the GMO constructs from carbon starvation was investigated in pure culture studies, and upon addition of starved cells to sterile soil. Pure culture studies clearly demonstrated a starvation-survival disadvantage of both the GMO constructs, as determined by growth and respiratory activity (dehydrogenase activity) when resuscitated from periods of starvation of up to 21 days. Correlation between dehydrogenase and luminescence activity was investigated. The lack of correlation between the two processes may have pointed to a change in maintenance energy costs as a consequence of genetic modification. Determination of the starvation-survival response in sterile soil was inconclusive, due to high variability and limitations to, and uncertainty in, cell extraction and culture. 572.8 Soil bacterium
2	The expression of Bt Cry1Ac in transformed cotton Bt Cry1Ac under abiotic stress Martins, Celia Marilia 03 November 2008 (has links) Bacillus thuringiensis (Bt) is a gram-positive common soil bacterium that produces crystals (Cry) containing proteins that are toxic to certain insects, in particular larvae of Lepidoptera and Diptera. The Bt toxin in the past has been widely used as a bioactive compound for the biological control of mainly lepidopteran pests. Most recently a variety of crops, including cotton and maize, have been genetically modified to express a Bt toxin to confer resistance to lepidopteran pests. However, the effect of abiotic environmental stress, such as drought and heat, which are typical for Africa, on Bt toxin expression in a genetically modified crop has so far not been fully evaluated. This study focuses on the expression and stability of the Cry1Ac insecticidal protein from Bacillus thuringiensis in genetically modified cotton plants under drought and heat stress. These include the physiological and biochemical characterization of the expressed Bt toxin gene under drought stress as well as the biological activity against first-instar larvae of the African cotton bollworm Helicoverpa armigera (Lepidoptera: Noctuidae). Non-genetically modified cotton (Gossypium hirsutum cv. Opal), as well as genetically modified cotton (cv. Nuopal) expressing the Bt toxin Cry1Ac, were exposed to drought and heat stress. Drought stress was induced by withholding watering plants until the soil moisture content reached 25- 30 % of field capacity. Non-stressed control plants were watered and soil moisture content to 80-100 % of field capacity was maintained. For heat stress, plants were grown at 38 to 32 DC during the day and night, respectively, whereas control plants were grown in a growth cabinet at a 28/25 DC day/night cycle. For growth analysis plants were harvested every second week after planting. At each harvest, different parts of the plant were collected and their fresh and dry weight determined. For biochemical analysis and determining biological activity against first-instar larvae of H. armigera, two types of experiments were carried out, the first experiment four weeks after treatment induction and the second experiment eight weeks after treatment induction. Different plant material (leaves, flowers and immature green bolls) were used for Bt detection as well as for determining biological activity against first-instar larvae of H. armigera. Under drought stress conditions a reduction in leaf area and leaf dry weight were found in both Bt toxin expressing and non-expressing cotton plants, but no significant difference in physiological performance between Bt-expressing and non-expressing cotton plants was found. This study shows that the Bt toxin (Cry1Ac) level decreases in senescent plants and that drought stress did not affect the growth and development of genetically modified Bt plants when compared to non-Bt plants. Although the expression of Bt toxin (Cry1Ac) in Bt cotton plants decreased under drought stress no effect on the efficacy of the toxin against H. armigera was observed. In addition, no significant decrease of Bt toxin content was found in Bt cotton leaves after exposure to heat stress when compared to leaves from nonheat stressed plants. / Dissertation (MSc)--University of Pretoria, 2008. / Plant Science / unrestricted Bacillus thuringiensis Gram-positive common soil bacterium Abiotic stress Lepidopteran pests UCTD
3	Purification, functional characterization and crystallization of the PerR peroxide sensor from Saccharopolyspora erythraea Elison Kalman, Grim January 2019 (has links) This report summarizes the work on the cloning, expression, and purification of PerR, a metal sensing regulator from Saccharopolyspora erythraea and the subsequent characterization using small angle X-ray scattering and other biochemical methods. The report aims to provide an insight into prokaryotic metal homeostasis, provide a better understanding of how PerR works and provide valuable information for the continued work on the crystallization of PerR. structural biology cell culture protein expression genetic engineering spectroscopy X-ray crystallography small angle X-ray scattering SAXS transcription factor PerR metal binding antibiotics Saccharopolyspora erythraea S. erythraea soil bacterium actinobacteria actinomycetes oxidative stress peroxide stress structure determination characterization stabilization peroxide sensor iron sensor manganese sensor metalloprotein metal ion homeostasis metal ion prokaryotic strukturbiologi cellodling proteinuttryck genteknik spektroskopi röntgenkristallografi småvinkel-röntgenspridning SAXS transkriptionsfaktor PerR metallbindande antibiotika Saccharopolyspora erythraea S. erythraea jordartsbakterie Aktinobakterier Actinobacteria Actinomycetes oxidativ stress peroxid stress strukturbestämning karaktärisering stabilisering peroxidsensor järnsensor mangansensor metalljonshomeostas metalljoner prokaryot Structural Biology Strukturbiologi

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