Isolation And Investigation Of Degradation Mechanism For Quizalofop-p-ethyl And Triphenyl Phosphate Degrading Bacteria

Quizalofop-p-ethyl?QPE?and triphenyl phosphate?TPP?are organic pollutants in chemical pollutants.In this study,the first strain,named YC-XJ1,was isolated from farmland near Sunan County Desert of Zhangye City,Gansu Province where herbicides were used for a long time.The second strain,named YC-XJ2,was isolated from sewage river bottom sludge polluted by e-waste in Guiyu Town,Chaoyang District,Shantou City,Guangdong Province.Through the observation of colony and cell morphology,the analysis of physiological and biochemical characteristics of Biolog,the phylogenetic analysis based on 16S rDNA sequence and analysis of average nucleotide identity?ANI?,the strain YC-XJ1 was identified as Methylobacterium populi,and the strain YC-XJ2 was identified as Sphingobium yanoikuyae.The effects of different environmental factors on the degradation ability of the strain was studied by single factor analysis.The optimal pH and temperature for QPE degradation by YC-XJ1 were pH8.0 and35?.Strain YC-XJ1 showed a certain tolerance to salt and high concentration QPE.Two new QPE metabolites,2-hydroxy-6-chloroquinoline and quinoxaline,were determined by HPLC-MS,and a more complete metabolic pathway was speculated.Substrate spectrum analysis showed that strain YC-XJ1could degrade 9 kinds of different AOPPs herbicides extensively.In addition,strain YC-XJ1 could effectively degrade diethyl phthalate?DEP?,dibutyl phthalate?DBP?,triphenyl phosphate?TPP?,tris?1,3-dichloroisopropyl?phosphate?TDCPP?,chlorpyrifos and phoxim.So many organic pollutants were first reported to be degradable by single Methylobacterium bacterium.The optimal pH and temperature for strain YC-XJ2 to degrade TPP were pH6.0 and 30?.The degradation rate of TPP with initial concentration of 100 mg/L was 99.7%after 24 hours,and the degradation ability of YC-XJ2 was much higher than that of previously reported strains.The degradation rate of TPP was 75.2%when the salt concentration reached 10%?g/v?,86.4%when the TPP concentration reached 500 mg/L,and YC-XJ2 showed excellent salt tolerance and substrate tolerance.Substrate spectrum analysis showed that YC-XJ2 could effectively degrade aryl organophosphorus flame retardants?aryl-OPFRs??such as TPP,2-ethylhexyldiphenyl phosphate?EHDPP?,tris?4-methylphenyl?phosphate?TCrP??and tris?2-chloroethyl?phosphate?TCEP?.The degradation of EHDPP by single bacteria was the first report.Soil bioremediation experiments showed that strain YC-XJ2 could significantly reduce the concentration of TPP in soil under natural conditions.This study provided a high quality degradation bacteria resource for the bioremediation of aryl-OPFRs contaminated soil.The complete genome sequence maps of the strains were obtained through genome sequencing.The evolution,variation and rearrangement of YC-XJ1 and YC-XJ2 were determined by genome collinearity analysis with their similar strains.Based on the annotation information,QPE degradation gene qpeh2 and TPP degradation gene sy-pte was screened and verified,and the degradation characteristics and enzymatic properties were systematically studied.The optimum reaction conditions of QPEH2 were 30?and pH8.0.Metal ions Cd²⁺,Pb²⁺,Zn²⁺,Ni²⁺,Fe²⁺,Co²⁺could inhibit activity of QPEH2.When QPE was used as substrate,the specific activity of enzyme was 0.01±0.002(U mg^-1),k_cat/K_m 0.18±0.0016(mM^-1·s^-1)and K_m 83.87±30.34??M?.Sy-PTE could degrade TPP,EHDPP,TCrP.the optimum reaction conditions were35?and pH7.0,and maintain 74.9%of enzyme activity when NaCl concentration was 8%?g/v?,only high concentration of Pb²⁺could inhibit activity of Sy-PTE.When TPP was used as substrate,the specific activity of enzyme was 66.97±0.2(U mg^-1),k_cat/K_m 4.8±1.6×10³(mM^-1·s^-1)and K_m 15.6±0.34??M?.