Effects Of Antibiotics On Microbial Community Structure Diversity In Typical Forest Soil

The occurrence and migration of antibiotics in soil have always attracted much attention,but the types of soil covered by relevant research are relatively limited,and there are few studies on antibiotic pollution in forest land and other types of soil.The"pseudo persistence"of antibiotics makes it have the characteristics of long-distance migration in environmental media,Therefore,whether the forest soil is polluted by antibiotics also needs attention,and it is necessary to study it.Through the combination of actual sampling and laboratory simulation experiment,the status of antibiotic contamination in the soil of Pinus tabulaeformis forest land with different antibiotic sources in Changping District of Beijing was explored,and the microorganisms abundance and characteristics of community structure under the exposure of different concentrations of sulfamethoxazole was discussed.The results show that sulfonamides,tetracyclines and macrolides were detected in different degrees in the three Pinus tabulaeformis forest soils;The highest detection rates of sulfonamides and tetracyclines were sulfamethoxazole and doxycycline respectively;The overall detection rate of macrolides was high,in which erythromycin,timomycin,roxithromycin and clarithromycin were detected in all samples,The detection rate was 100%;Among the three kinds of antibiotics,sulfamethoxazole,oxytetracycline and erythromycin had the highest detectable concentrations,which were 104.65,92.73 and 2.26μg·kg^-1 respectively;The natural degradation of sulfamethoxazole with different concentrations was simulated in the laboratory,and all the half-life was less than 2d;There are great differences in the abundance and structural composition of soil microorganisms in various places,and theαdiversity index of community structure were also significantly different,but the most dominant fatty acids were 16:0 which representing general bacteria;Microbial abundance is positively correlated with TOC,TN and other physical and chemical properties.The existence of antibiotics may have a negative impact on microbial abundance and structure.Furthermore,through a 21-day indoor culture experiment,it was found that soil microorganisms had different responses to different concentrations of sulfamethoxazole exposure;Under the low concentration of 0.5μg·kg^-1,the soil microbial activity was promoted temporarily,and the microbial abundance showed a slight upward-downward trend;However,under the high exposure concentrations of 50 and 5000μg·kg^-1,microbial abundance showed a downward-upward-downward trend.The decline of microbial abundance in the last stage（14～21 d）of all test groups was related to the lack of nutrients such as carbon source in the experience;After exposure,the microbial Shannon-Weiner diversity index of all exposure groups decreased significantly compared with the control group.