Plant-root interaction occurs in the rhizosphere, a region referred to as a biologically active zone of soil where microorganisms and plant roots interact. This study examined the impact of genetically modified (GM) maize (Bt) on functional community of rhizobacteria. Soil samples of field grown GM and non-GM maize were collected from an experimental field in Delmas, South Africa, at 30 days after sowing (DAS) and I day after harvest (DAH). Chemical analyses of soil properties in GM and Non-GM soil samples were performed. Quantitative analysis was achieved through soil dilution and plate count (colony forming units) using selective and non-selective media (tryptic soy agar, nutrient agar, Luria Bertani agar and Pseudomonas selective agar). Qualitative analysis was achieved using analytical profile index identification systems and sequence data of rhizobacterial isolates. Biolog GN2 microplate was used to compare community catabolic profile of rhizobacteria in GM and non-GM soils and denaturing gradient gel electrophoresis technique (DGGE) was used in comparing rhizobacterial community profiles in GM and non-GM soil samples. Chemical analyses of GM and non-GM soil samples collected 30 DAS and 1 DAH indicated the same elements with similar percentages. The pH of GM and non-GM soil samples range from 6.12-7.03, indicating slightly acidic to slightly alkaline soil. Total count of rhizobacteria (cfulg) in GM and non-GM maize soil samples collected 30 DAS and 1 DAH was not significantly different in the media. Similar rhizobacterial species from the rhizosphere of both GM and non- GM maize were identified using analytical profile index and sequence data. No significant difference was observed in the community catabolic profile among the rhizobacteria in GM and non-GM soil samples. Cluster analyses of DGGE bands indicated that band patterns of GM and non-GM samples 30 DAS and 1 DAH were similar to each other. These findings suggest that the GM maize was not able to alter microbial community and activity and are significant to the investigation of the impact of GM maize on rhizobacteria. / Thesis (M.Sc. (Biology) North-West University, Mafikeng Campus, 2013

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The effect of <I>L. terrestris </I>on the transport of marked bacterial inocula in the absence of percolating water was investigated using repacked soil microcosms over a 10 day period. The microcosms consisted of cylindrical cores containing loamy sand. The bacterial inoculum was applied in filter paper disks to the surface of soil cores containing <I>L. terrestris </I>and to control cores. Destructive analysis of cores was carried out 5 and 10 days after inoculation to facilitate enumeration of marked bacterial inocula at 3 depths in the soil. Significantly greater vertical transport of marked bacteria occurred in cores containing <I>L. terrestris. </I>The effect of <I>L. terrestris </I> on the dispersal of marked bacteria in the presence of percolating water was investigated using both repacked soil cores and larger intact cores over a one month period. Bacterial inocula were again applied in filter paper disks to the surface of cores and the cores subjected to simulated rainfall events at 3 day intervals. Concentrations of marked bacteria in leachate were determined and destructive harvests of cores carried out after 24 days. The results from repacked soil cores demonstrated that cores containing earthworms were associated with early breakthrough, higher percentage recovery and greater numbers of marked bacteria in the leachate than control cores without earthworms. Results from intact soil cores demonstrated that cores containing earthworms were associated with different bacterial leaching patterns, higher percentage recovery and greater numbers of bacteria in the leachate than control cores. For both repacked and intact cores, the presence of earthworms in cores led to transport of marked bacteria to greater depths in the soil. Plaster of Paris impregnation of repacked and intact cores highlighted the importance of earthworm burrowing in providing pathways for bypass water flow and hence bacterial transport through soil. Results from the use of interdisciplinary methods developed and adapted in this study identify the importance of earthworms in the fate of microbial inocula in soil and the potential for use of earthworms in biotechnology.

Survival of P. fluorescens 10586s FAC510 was studied in liquid culture and soil microcosms in the presence of the ciliate C. steinii and the flagellate Cercomonas sp. Both protozoa caused a reduction in bacterial viable cell concentration, however the ciliate caused a greater decrease in abundance. Starvation of the bacterial prey caused a reduction in grazing rates of both the ciliate and flagellate, indicating the lower nutrional quality of starved as opposed to non-starved cells. Manipulation of the physiological state of prey cells, by starvation, had much the same effect as observed when bacterial prey resources are reduced. Luminescence provided a valuable marker for monitoring P. fluorescens 10586s FAC510 in liquid culture and soil, since detection by luminometry provided a sensitive, rapid, and non-extractive technique for measurement of microbial activity. In the presence of C. steinii, bacterial activity increased, whilst predation by Cercomonas sp. caused a reduction. The different responses of the bacterial inoculum may reflect the divergent balance between bacterial turnover, leading to nutrient regeneration, and grazing strategies, which are selective of the two protozoa. The distribution of bacterial cells in the soil pore network was manipulated by adjustment of the antecedant matric potential prior to inoculation. The ability to predominantly place bacterial and protozan cells in specific pore size classes was confirmed by partial chloroform fumigation and resin impregnated sections of soil.

Introduction: The Genetically Modified (GM) food, which is one of the fruit of the modern biotechnology, is closely related to people's lives. GM food, specifically, GM crops, also known as biotech food, are produced from genetically modified organisms (GMO), which use genetic engineering techniques to introduce, recombine and modify DNA. The safety of GM food still do not have final conclusion at present. Although GM food has been introduced into China for over 15 years, many of the surveys show that Chinese consumers‘ knowledge of GM food is relatively low comparing with other countries. In 2002, China‘s Ministry of Agriculture promulgated three regulations to manage the GMOs in China. The attitudes and acceptance of market for GM food have direct impact on the development of genetic engineering technique and government‘s policy making. This review aims to investigate cognition and attitudes of GM food among Chinese consumers; to investigate how the consumers react to the GM food labeling policy; to find out how factors such as knowledge about transgenic information, price of GM food would affect the consumption of GM food. Methods: Relevant studies published between January 2002 and May 2013 were searched and identified through NCBI, CNKI, and Google Scholar with a combination of keywords, such as “GM”, “China”, “attitude”, “knowledge”, and “willingness” both in English and Chinese. Studies regarding the average knowledge level, acceptance and willingness-to-pay (WTP) for GM food among Chinese consumers, and factors affecting the WTP were included. Results: Of 1032 papers identified, 9 articles fulfilling the selection criteria were included in this systematic review. Among the 9 articles, 7 were written in English, 2 in Chinese. Awareness and knowledge of GM food among Chinese consumers were still not satisfying. Given the potential risks, the public tended to hold divergent attitudes to GM food, which had significantly influenced the WTP. Socio-economic factors such as the number of children, and external factors such as information and price also affected the WTP. Among all the factors, positive attitudes (including willingness-to-accept WTA), and positive information about GM food have significant positive influence on the WTP of GM food, while consumer‘s number of children, price of GM food and negative information about GM food would reduce the purchase intention. Discussion: Positive attitudes (including willingness-to-accept WTA), and positive information have significant positive influence on the WTP of GM food, while increasing number of children and price of GM food and negative information would reduce the purchase intention. It is necessary to strengthen the comprehensive and objective propaganda of GM food and transgenic technology; enhance the management of GM food; plan and develop GM food industry with focus on low-income consumers for they are more willing to buy GM food. / published_or_final_version / Public Health / Master / Master of Public Health

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