Resear Ching On Soil Antibiotic-resistance And Eff Ects Of Antibiotics On Soil Nitrogen

In this dissertation,We studied antibiotic resistance genes and strains in different soils through traditional methods of microbial ecology and molecular biology research methods as well as referring to the methods of clinical medicine.And we also explored the effects of antibiotics on soil nitrogen.Systematically studied the internal relation between the use of antibiotics and the soil antibiotic-resistance.Main conclusions are presented as follows:All the soil samples provided great opportunities for horizontal resistance transfer.Forest soil with low absolute and relative copy number of resistance genes.Although the absolute copy number of resistance genes in tea garden soil is low,the relative copy number is comparatively high.Class 1 integron gene widely exists in the soil environment,while class 2 integron gene only exists in the tea garden soil,pasture soil and pig manure.And the gene copies considerably below Class 1 integron gene.The potentially large and diverse pool of antibiotic resistance genes may have considerable implications for ecology and health.There are various degrees of the penicillin and tetracycline resistance bacteria in four diverse soils.Moreover,we identified super penicillin-resistant strains in four diverse soils containing up to 1000 mg/L penicillin,which is the highest concentration of exogenous penicillin reported to date.Twenty bacterial isolates were selected,representing a diverse set of species in the genera Pseudomonas sp.and Variovorax sp.,these bacteria showed multiple antibiotic resistance patterns for four or more antibiotics.The resistance genes tet(C)and blaTEM were fairly widely distributed in these penicillin-resistant isolates,and some resistance genes are located in plasmid.Antibiotics did affect the change of soil nitrogen,however with the passage of time,the soil restored balance.Copies of ammonia-oxidizing archaea(AOA)showed a gradual downward trend under 50 mg/kg antibiotic treatments,while under 1 mg/kg antibiotic treatments,the copies of AOA declined first then activated and finally declined gently,which correspond to the change of soil nitrogen in the initial cultivation stage indicated that nitrification was mainly driven by AOA under the pressure of antibiotics.While the specific mechanism of antibiotics on soil nitrogen remains to be explored further in many respects.