Study Of The Degradation Of Sulfonamides In Rhizosphere And Microbial Response Mechanism

Sulfa drugs (SAs) is a class of of synthetic broad-spectrum antimicrobials with the aminobenzenesulfonamide structure. Given its characteristics of low protein linding and spreading, the drug is theprincipal choice for prevention and treatment of bacterial infectious diseases. Currently, being used aslivestock and poultry feed additive drugs, the production and consumption is so huge. But the SAs is noteasily to absorb and decompose, while60%to90%of the drug will be excreted from the body. The residueinfluences the soil environment and ecosystem safety through manure into the soil.This study established the extraction of sulfadiazine (SD), sulfamethoxazole (SMZ) sulfamonomethoxine(SMM) and phospholipid fatty acids (PLFA) of soil microbial flora. On this basis we researched thedegradation process of SAs in millimerer rhizosphere and mechanisms of biological responses to the drugstress.Using batch equilibrium method, three kinds of SAs (SD, SMM, SMZ) in the control of soil and add thesecretion of root system in soil degradation and the response mechanism of microbial community hascarried on the exploration, the results showed that the degradation of three drugs CKtt=C0epseudo-first-order reaction kinetics equation. And add the secretion of root in the soil is bigger than thedrug degradation rate of blank soil. Rate order: three kinds of veterinary drugs of sulfamethoxazole>sulfanilamide between a oxygen pyrimidine> sulfadiazine, after first fast and slow degradation of L typecurve. Root secretion can significantly stimulate the soil microbial growth, microbial community havecertain differences of three kinds of drug toxicity response, total peak in flora under the stress of SMZappear late (35days), but the fungi and actinomycetes under all the stress was a large increase, he appearedat the early stage of the training, and plan in this sensitive to pollution stresses the heavy pressure ofpsychrophilic bacteria, microbial community in the direction of the transformation to slow down thetoxicity of intimidation. The existence of root secretion can improve the soil environment.By studing to the degration of SD in millimeter rhizosphere and microbial community diversity, it wasfound that crop rhizosphere and non-rhizosphere soil microbial communities had significantdifference.Compared to wheat, corn rhizosphere effects more strongly. Wheat are more likely to get damaged than corn, and corn has stronger resistance, better resilience. The structure of microbial inmillimeter soil transforms regularly by the influence of crop growth and the root exudates which play animportance role in SD degradation. Monomer PLFA14:0, a15:0, i16:0, i16:1, a17:0,10Me18:0,18:1w9c,16:1w5c with SD abatement was a significant positive correlation (p <0.05). The lower the concentration is,the faster degradation should be, the shorter the half-life is. SD in the rhizosphere soil degradation rate isgreater than the non-rhizosphere soil. Grown plants can greatly improve soil degradation conditions, thesynergy of plant roots and microbes can be more effective in promoting the degradation of SD. Monomeri16:1in wheat and corn soil cutting has a larger contribution to the SD, which further confirmed by SDpollution of natural soil. Some floras plays an important role to SAs degradation.Experimental test results showed that the corn rhizosphere microbial overall increased and thendecreased with SD concentration. The rhizosphere microbial communities showed activation effect at lowSD concentrations (1-2mg·kg-1), while showed the inhibition-activation–inhibition effect. Totalnon-rhizosphere soil PLFA gradually decreased with the increasing concentrations of SD. In rhizospheresoil,it showed bacterial biomass> fungi> cyanobacteria> actinomycetes> methane-oxidizing bacteria. Thecontention of indicative PLFAs of environmental stress (such as toxicity, pollution, oxygen pressure) was5mg·kg-1>2mg·kg-1>1mg·kg-1> controls. The siol total PLFAs has Significant correlation with thedegradation rate (p<0.05) at low concentrations. When exposed to high concentrations with time, the totalmicrobial biomass increased and then decreased, and the degradation rate increased, which may be relatedto natural selection and survival of the fittest. Fungi and actinomycetes were likely to differentiate vastnumbers of SD strains, but the species structure of belonging needs further research.