GFP-Labelling And Colonization Of Mineral-Weathering Bacteria And Its Effect On Mineral Weathering

In the soil, microorganisms, minerals and plants formed the relationship of the interdependence and mutual effect. The interaction of microorganism-mineral-plant system affects the dissolution of mine and formation of soil. Little is known about colonization and populational dynamics of mineral-weathering bacteria on the plant and its effect on mineral weathering with plant. So, studying on this aspect provides the evidence for expolring the relationgship among microorganisms, minerals and plants, and have an influence on researches of the geochemical cycle of mineral elements.22 bacteria which have the ablity of producing indole-3-acetic acid (IAA) and siderophores are picked up. After growth-promotion experiments which making use of seeds of rice and wheat, the results showed that about 45% of strains reflect the growth-promotion property on the rice seeds, only 27.2% of strains have the same function on the wheat seeds. From those strains, Pantoea sp.W19 was chosen for gfp-lablling. A plasmid pKGL3 containing gfp gene and Tn5 were introduced into Pantoea sp. W19 by tri-parental mating and 16 gfp-lablled bacteria were obtained.In comparision with the wild type strain, the growth mate and biomass, the ablilty of producing in indole-3-acetic acid (IAA) and siderophores and mineral weathering of g/p-lablled strains were affected slightly. The gfp were transferred to W19 chromsome. Strains 19G-3 and 19G-16 were selected for the next experiment.The results of colonizational dynamic experiment showed that 19G-3 and 19G-16 can colonized on the rice root surface, and the number of colonization of 19G-3 is more than 19G-16. Both of them can maintained up to 105 cfu·g-1 root at 19 d after inoculation. The majority of the gfp-lablled bacteria colonized on the root top surface and only a minority of them resided in the root bottom. With the growth of root, the strains had the trend of downward tranferring. Also the strains can colonize in the root and the stem of rice in a period.Two tested strains were used in the experiment of plant growth-promoting and mineral weathering. Pronounced differences in the the length and the biomass of roots and stems for rice inoculated with 19G-3 and 19G-16 compared to the control were detected 8 weeks after root inoculation, indicating a longer-lasting effect.With the treatment of biotite, the root length and biomass of rice inoculated with bacteria were increased. With the treatment of feldspar and 1/5 potassium nutrient solution,19G-3 and 19G-16 evidently improved the length and the dry weigh of rice’s roots and stems. With the existence of biotite or feldspar and 1/5 potassium nutrient solution, a great inerease was also found in Si and K concentration of rice inoculated with bacteria. With the existence of feldspar and biotite, Si and K uptake by rice inoculated with bacteria were increased significantly. Microscopic observation of the root hair using stereo microscope showed that the root hair inoculated with bacteria were much longer and thicker than the control.The results of X-ray diffraction analysis on mineral showed that, plant inoculated with bacteria 19G-3 and 19G-16 can promote dissolving the feldspar and biotite, and the biotite was under the change of vermiculitization. The results of EDS on mineral which lied on the surface of root demonstrated that the relative contents of Fe and Na were much higher in the tiny particles than the surface of mineral. A particulate form of new secondary mineral maybe occurred when plant inoculated with bacteria interacts with silicate rocks.