Isolation,Characterization And Metabolic Mechanics Of Arthrobacter Sp. C2

Atrazine had been the champion of herbicide since it was introduced for controlling the weeds.Recent years,many developed countries had banned this herbicide for its effect of hormone disruption.However,it was still common for the majority of farmersfromdeveloping country to make use of atrazine to control weeds because of its cheapness and great herbicidal ability.Atrazine could easily enter into surface water and groundwater by runoff and leaching for its good water solubility and low adsorption coefficient,thus causing global ecological impact.Atrazine may cause reproductive toxicity because it possessed endocrine disrupting effect,so it was of great significance to explore the best remediation to remove the atrazine contaminants.In this article,a strain can degrade atrazine was isolated from Jilin maize soil and used to explore degradation characteristics?possible metabolic mechanism and the effect of bioremediation.The results as follows:A strain capable of utilizing atrazine as sole source of carbon and nitrogen was isolated from atrazine contaminated soil.Isolate C2 could grow well in the mineral salt medium with 10 ?g/ml atrazine,readily degraded 90% of initial atrazine in 3 days,C2's growth rate slowed down after 5 days incubation,the growth was highest in the 9th day.Based on the transmission electron microscope and 16 Sr DNA gene sequence,strain C2 was identified as Arthrobacter sp.The degradation characteristic of atrazine by the strain C2 mainly depends on substrate concentration?pH and temperature.On the one hand,it was not obvious of different substrate concentrations for effect upon the degradation,all three treatments could completely degraded atrazine after 3 days incubation.Ranging from 1 ?g/ml to 100 ?g/ml,Among the three treatments,degradation performance under 100 ?g/ml atrazine was the best.the degradation rates were positively correlate with the substrate concentration.Among the three treatments,degradation performance under 100 ?g/ml atrazine was the best.on the other hand,it was significantly obvious of pH and temperature for effect upon the degradation.Under the condition of pH5.0(30??10 ?g/ml?150rpm),the degradation rate was only 10% after 5days incubation.Otherwise,under the condition of 40?(pH7.0?10 ?g/ml?150rpm),the degradation rate was 22% after 5days incubation,which was not significantly different from the control.The results showed that the effect of degradation by strain C2 would be restrained under the condition of acid and high temperature.In summary,the atrazine degradation rates at different substrate concentrations,pH and temperature followed the order of 100 ?g/ml>10 ?g/ml>1 ?g/ml,pH7.0>pH9.0>pH5.0,30?>20?>40??the best condition for degradation by strain C2 was 30?and pH7.0.The degradation of atrazine by strain C2 mainly include hydrolysis and dealkylation.The metabolites of atrazine by isolate C2 were hydroxy atrazine(?),N-isopropylammelide(?),cyanuric acid(?)and deisopropyl hydroxy atrazine(?).Strain C2 could not degrade cyanuric acid,which was basically fit with other study upon Arthrobacter sp.The results of bioassay showed that the strain C2 has obvious capacity of removing the pollution of atrazine.In hydroponic experiment,comparing to the wheats in the same atrazine concentration without inoculation treatment,the plant height,root length,fresh weight and dry weight of wheats was increased by 50%,49%,58%and 30%respectively in treatment with atrazine and inoculation.In soil experiment,comparing to the wheats in atrazine treatment without inoculation,the plant height,root length,flesh weight and dry weight of wheats was increased by 47%,73%,156%and 64% respectively in treatment with atrazine and inoculation,and the wheats in atrazine treatment with inoculation was basically identical with the control(without atrazine and inoculation).The results showed that the strain C2 could cut back the side effect on the wheats growth caused by atrazine.