Plant Growth-promoting Rhizobacteria Pseudomonas Monteilii PN1 On PNP-degrading And Bioremidation Of Contaminated Soil With Clovers

In recent years,nitroaromatic compounds are widely used as raw materials or intermediates in chemical production. The pollution of nitroaromatic compounds became increasingly serious duing to discharging industrial wastewater and extensive using of organophosphorus pesticides. It not only damagde the environment but also influenced human health and the survival of mammals. Because nitroaromatic compounds are stable and absorbent to soil, so it was difficult to degrade in nature. But some micro-organisms obtained the ability of nitrophenols degradation after a long period of contact and domestication, and also processed the bioremedation potential of contaminated soil with plants. Therefore, bioremediation has become an popular issue. Bioremediation is not only fast, efficient and economical, but also avoiding secondary transfer of pollutants, indicating its broad development prspect.In this study, an efficient PNP-degrading bacteria had isolated from a farmland treated with pesticides in Changchun. The bacteria,which named PN1, was identified as Pesudomonas by 16 S rDNA sequence analysis. PN1 could degrade PNP as the sole carbon and nitrogen source with a concentration range of 0~200 mg/L in which showed high hydrophobicity and permeability. Simultaneously, PN1 also had kanamycin, chloramphenicol resistance and metals tolerance with the minimum inhibitory concentration 700, 500, 800, 100 mg/L for Cd2+、Pb2+、Zn2+、Cr6+.According to the antibiotic resistance, PN1 was tagged with green fluorescent protein gene(gfp) and showed stability. Subsequently, the axtivity of the gfp-tagged strain and its survival were studied in soil microcosm. Results showed PN1-gfp chould degrade PNP of 141.61 mg/L after 160 h with stable green fluorescence indicating its potential for actually contaminated soil.Secondly, the plant growth promoting properties of PN1-gfp were explored, including indole acetic acid(IAA), siderophores, dissolving phosphorus insoluble, 1-amino-cyclopropane-1-carboxylic acid(ACC) deaminase activity, to prove it was plant growth-promoting bacteria(PGPR). Then alfalfa growth experiments in MS solid medium, the maximum tolerable concentration did not dip PNP bacteria alfalfa is 20 mg / L. When the PNP concentration of 20 mg / L when the inoculation of alfalfa, since PN1-gfp degradation of PNP reduce the toxicity of the plants were growing much better than not inoculated alfalfa and PN1-gfp promote stem effect is more obvious.Finally, pot experiment showed the optimum concentration of PNP for clovers in soil was 100 mg/kg. After 30 days, natural degradation rate of PNP was about 18.1 %, rhizosphere and non- rhizosphere degradation rate of PNP were about 31.0 % and 29.9 % due to the role of clovers, while rhizosphere and non- rhizosphere degradation rate of PNP were about 89.0 % and 85.8 % due to the role of clovers and PN1-gfp. In clovers pots treated by PN1-gfp, biomass in rhizosphere soil was significantly more than non- rhizosphere soil. Simultaneously, in clovers interior, the biomass of root was more than leaf and stem.