Effects Of Rhizosphere Environment On The Interaction Of Bacillus Cereus And Leersia Hexandra Swartz In Purification Of Cr(?) In Water

Chromium is a very harmful environmental pollutant,the harm of chromium-contaminated water cannot be underestimated for the ecological environment and human health.Method for water environment management and restoration,Plant and microbial synergistic repair technology has significant advantages.Leersia Hexandra Swartz is a chromium-rich plant widely distributed in southern China.Highly abundant Bacillus cereus that can tolerate high concentrations of chromium stress was found at its rhizosphere.Exploring their possible interactions to improve the efficiency of repairing chromium pollution water,enriching and perfecting the theory of plant-microbial absorption of chromium.The results are as follows:?1?Under the stress condition of 10 mg/L Cr???,hydroponics L.Hexandra with Bacillus cereus and antibiotics respectively,GC-MS spectral analysis showed that there were 19 root secreting compounds in the bacteria-treated group,most of which were alkanes compound.There were only 6 compounds in the non-bacterial experimental group,the types and contents of alkane organic compounds were reduced,and the carboxylic acid content was as high as53.29%.It shows that in the absence of bacteria,organic acids play a major role in the reduction of hexavalent chromium in the system.Bacillus cereus had a positive effect on L.Hexandra and promoted the production of root exudates under heavy metal stress.?2?Comparison of the reduction of Cr???in water by different substances by hydroponic L.Hexandra experiment,The results confirmed that the reduction effect of L.Hexandra and Bacillus cereus was higher than the blank group and single substance.In addition,the growth of Bacillus cereus was better under the condition of coexistence with L.Hexandra,it indicated that the root exudates promote the growth of Bacillus cereus to some extent.?3?The best rhizosphere environment for the reduction of Cr???by L.Hexandra-Bacillus cereus system was as follows:temperature:32-37°C,pH 7.3,dissolved oxygen concentration was 4 mg/L;high concentration of root exudates contributed to the reduction of Cr???;the best form and concentration of nitrogen and phosphate fertilizers were 20 mg/L?NH₄?₂SO₄ and 10mg/L?NH₄?₂HPO₄,potassium fertilizer effect was not obvious.Excessive organic fertilizer would have a counter-effect on the system and the repair efficiency was reduced.?4?The biological characteristics of bacteria showed that Bacillus cereus had the ability to produce IAA and phosphorus-soluble,and the content of ACC deaminase and siderophore was higher,so it has many excellent growth promoting properties.The soil culture experiment also showed obvious promoting effect on the L.Hexandra's plant.