Selection Of Cadmium Tolerant Bacteria And Preliminary Study On Cadmium Resistant

Cadmium is one of highly toxic elements. It is very easy to be absorbed from soil by crops, which seriously threat human health through the food chain. The Study found that some bacteria has strong application prospect in the remediation of heavy metal contaminated soil.This study screened a strain on the Cadmium maximum tolerance concentration was about30mmol/Lof bacteria through the gradient experiment of Cadmium, named Dl; D1not only has strong tolerance to Cadmium, also has a strong resistance to other heavy metals, in the LB medium maximum tolerance concentration of Zn2+, Cu2+, Pb2+, Ni2+, Cr6+ions were15,17,11,4,0.3mmol/L.The bacterial morphology observation indicated that D1colonies were yellow, opaque, round, thick, smooth surface, easy to provoke. Microscope observation showed that D1oval, without flagellum, a capsule, about the size of (0.6-0.9) X (1.0-1.5) μm. Through the physiolo-gical and biochemical analysis showed that the D1is gram positive coccus; antibiotic resistance test showed that D1of colistin (300IU) highly resistant, antibacterial circle above20mm; penicillin (10IU) and low sensitive to the10antibiotics (antibacterial circle≤10mm). At the same time, the D1is analyzed and identified16S rDNA sequences, results show that the gene sequence and Bacillus similarity99%, initially identified as bacillus.For optimum growth conditions on D1under Cadmium Stress of groping, found the Dl optimum conditions for growth under Cadmium stress were35℃, pH=5.0. Determination of the Cadmium stress, other metal ions Cadmium resistance training effect of D1medium in LB liquid; the results revealed that the addition ofa certain role in promoting the growth of Zn2+, Cu2+ions on D1, Ni2+, Cr6+ionhas a strong inhibitory effect, the role of Pb2+is not too clear. Cadmium resistant characteristics of Cadmium tolerant bacteria were studied, results showed that LB liquid D1in Cadmium ion concentration of0.5mmol/L in the medium,48h after sampling, cultivation of Cadmium ion concentration in the medium decreased5.9%, showed that D1not only has strong Cd tolerance,there is still a certain the adsorption capacity of Cadmium ion; training in higher in (1mmol/L), enhanced D1removal capacity of Cadmium, Cadmium removal rate reached9.1%, indicating that D1can be used to repair the Cadmium pollution environment.