Effect Of Bt Transgenic Rice (KMD) At The Booting Stage On Anaerobic Microorganisms, Biochemical Processes And Bacterial Diversity In Flooded Soil

The problem of ecological safety arisen by transgenic plants has been one of most attractive focuses around the world. In this thesis, the effects of Bt-transgenic rice (named "Kemingdao") straw on the anaerobic microorganisms, biochemical processes and bacterial diversity in flooded paddy soil were investigated. The main results were as follows:1. Effect of "Kemingdao" straw on the number of anaerobic microorganismsThe influence of "Kemingdao" straw on the number of anaerobic microbial populations in paddy soil was investigated by using anaerobic MPN (The Most Probable Number) method and the improved Hungate anaerobic technique. The results showed that the "Kemingdao" straw could increase the number of hydrolytic-fermentative bacteria (P0.05) and anaerobic nitrogen-fixing bacteria markedly. The number of denitrifying and methanogenic bacteria, however, was decreased obviously (P0.05).2. Effect of "Kemingdao" straw on the activity of soil enzymesThe effects of "Kemingdao" straw on the activities of soil enzymes were also studied. The results indicated that a significant advanced effect was observed on the activities of phosphatase and cellulase (P<0.05) in short term, however, the activities of dehydrogenase and methane formation were seriously inhibited (P0.05) in short time after retuning of transgenic rice straw into flooded soil, but after treatment for 56d and 44d, respectively, the activities of dehydrogenase and methane formation in soil with Bt transgenic rice straw were significant higher than those in soil with non-transgenic rice straw.3. Effect of "Kemingdao" straw on the bacterial diversity in paddy soilIn order to investigate the effect of "Kemingdao" straw on the bacterial diversity in paddysoil, one of innovative molecular ecological methods, Polymerase Chain Reaction-Denaturation Gradient Gel Electrophoresis (PCR-DGGE) method was used to compare the difference between the treatments with Bt-transgenic "Kemingdao" and non-transgenic rice straw. Both of Shannon and Pielous indexes revealed that there were transient differences in the bacterial community composition between soils amended with Bt transgenic rice straw and soils amended with non-transgenic rice straw over the short time soil incubation.4. Effect of Bt transgenic rice straw on the diversity of methanogenic bacteriain paddy soil16S rDNA fragments of methanogenic bacteria were amplified by differential primer and analyzed by PCR-DGGE. Both of Shannon and Simpson diversity indexes showed that the Bt transgenic rice straw could decrease the methanogenic bacteria diversity in former time of incubation and increase in later time of incubation.5. Comparison of four soil DNA extraction methodsFour soil DNA extraction methods were compared in isolation of the total microbial DNA from five types of soils. The four methods were evaluated comprehensively for their yields, purity of DNA extracted from different soil samples and the effect on the subsequent Polymerase Chain Reaction-Denatured Gradient Gel Electrophoresis (PCR-DGGE) analysis of the bacterial community. The results showed that the highest soil DNA yields was obtained by the SDS-high strength salt method and the best DNA purity by the DNA extraction kit method. Based on the PCR-DGGE analysis, the DNA extracted by the DNA extraction kit method provided a more bacterial community diversity than the others and the SDS-phenol/chloroform method did a poorer one.