Biodiversity And Functional Study On The Endophytic Bacteria In The Seeds Of Tobacco K326

Endophytic bacteria could live in the host for a long time and co-evoluted with the host. The host could provide the nutrition and living condition for endophytic bacteria and the bacteria could give some important affection on the host with its secreted products. Tobacco is a very important economic crop in Hunan province and is the major income source for the families in the backcountries. K326is one of the leading varieties in Hunan province because of its prominent agronomic trait and economic characters. The endophytic bacteria is the system component of the host and it is still an un-resolved question that how does these microbes effect the host.The main results of this thesis including:1. There was a relative rich bio-diversity of the cultivable endophytic bacteria in the seeds of K326. We isolated a total of147endophytic bacteria strains using4mediums with different nutrition components and selected50strains based on the morphology character for16S rDNA sequencing. The classification of16S rDNA showed that the dominant endophytic bacteria of K326were Stenotrophomonas, Pseudomonas and Bacillus.2. We tested28strains for the ability to synthesis and secret siderophore. The results showed that24out of28tested strains had the siderophore activity and K044and K037had the highest activity (>60%).3. We test the antibacterial of28isolates of endophytic bacteria with Ralstonia solanacearum and P. nicotianae and12out of28isolates showed a positive antibacterial activity against R. solanacearum. The most two prominent isolates were K044and K037, with26mm and23mm of the diameter of antibacterial circle respectively. The isolate K044and K037show a strong antibiology activity against P. solanacearum also. The results of plasma emission spectrum showed that the concentration of Ca2+rose quickly after treated with culture broth of K044, and there was abundant of bubs on the cell membrane and then the cell became dried after the cell membrane broken. These results indicated that the mechanism of antibacterial activity against R. solanacearum lies in the ability to attack the cell membrane of the pathogens. The cytoplasm of P. solanacearum significantly isolated from the cell wall after treating with the cultural broth of K044and a complete plasmolysis after24h. We proposed that the antibacterial products could destroy the cell membrane of P. solanacearum and lead to the exosmosis.