Effect Of Enrofloxacin On The Functional And Structural Diversity Of Soil Microbial Communities In The Indoor Vegetable Model

Soil microorganisms are one of the most important roles in ecosystems,studying the diversity of soil microbial function and structure can reflect the health status of soil to a certain extent and predict soil quality changes earlier.In this study,Biolog-Eco Plate method and phospholipid fatty acids method(PLFAs)were used to investigate the functional and structural diversity of soil microbial community at different enrofloxacin concentrations(20,200,2000?g/kg)in the indoor vegetable models(pig manure-soil)in different culture times(1,7,14,30,and 50 d).The results of metabolic functional diversity of soil microorganisms show by Biolog-Eco Plate method that average well color development(AWCD),Shannon index,Simpson index,Mclntosh index,Richness index at the beginning of the experiment(1,7 and 14 d)were promoted at the low and medium concentrations group of enrofloxacin(20,200?g/kg),and the 20?g/kg group was significantly different from the control group at the same sampling time(P<0.05),while the high concentration(2000?g/kg)groups were not(P>0.05).On the30th and 50th day of the experiment,the enrofloxacin groups showed the inhibitory effect on the metabolism of carbon sources,and the higher the concentration,the stronger the inhibitory effect.The principal component analysis(PCA)showed that the soil microbial carbon sources of the samples at different sampling times differed under different concentrations of enrofloxacin.Carboxylic acids,carbohydrates and amino acids were the main groups in carbon sources utilization and in the short term,the low concentration groups promoted the carbon sources utilization and the high concentration groups inhibited carbon sources utilization under the pressure of different concentrations of enrofloxacin.The results of PLFAs study on soil microbial structure diversity show that a total of 19phospholipid fatty acids were identified in the test,of which the most were C16:0,C18:0 and10MeC16:0.Bacteria are the most abundant in the distribution of microbial structures,followed by actinomycetes and the fungi are the least abundant.Among bacteria,G~+is mostly.The total microbial fatty acids content in the high-concentration group(2000?g/kg)on the first and the 14th day of each enrofloxacin group was significantly lower than that of the control group(P<0.05).There was no significant difference in the samples at other time(P>0.05).The G~+and G~-contents were lower than the control groups except for the 7th day and the 50th day in the whole test,but only the 1st day's drug groups were significantly different from the control group(P<0.05).G~+/G~-values were not significantly different during the entire test period(P>0.05).Actinomycetes and fungus contents were significantly lower on the first day than on other samples but after the 7th day,all groups began to increase.Principal component analysis(PCA)showed that different concentrations of enrofloxacin led to changes in the structure of the soil microorganisms.Samples at a single sampling time showed high degrees of dispersion on days 1,7,and 14.The time distribution results show that the 1st,7th,and 14th samples are also very discrete in spatial distribution,and after 30days,the differences between the groups gradually decreased.