The Interaction Effects Between Doxycycline And Soil Microbial

This study used doxycycline(DOX) as model veterinary antibiotic to study the interaction effects between antibiotic and soil microbial. This research could provide basis data for the ecotoxicological effects of the veterinary.The experiment was conducted in the 2 L beakers with a constant temperature of 25℃ and moisture content 78.0%. According to the different initial concentration of DOX in the soil, this study was divided into 6 groups(0mg/kg, 4.4mg/kg, 8.0mg/kg, 10.9mg/kg and 13.2mg/kg), each group included sterile and non sterile treatment. Each treatment has three replicates. Once the experiment started, the soil moisture content need to be maintained by suppling water every 3 days. The trial was lasted for 29 days to determine the concentration of DOX, main metabolic products, the copies number of microorganism and antibiotic resistance genes.The main results of this paper are as followed:1. The addition of DOX could influence the copies number of bacteria and actinomyces, and the initial concentration of DOX at 4.4-10.9 mg/kg might result in the more significant inhibition effect. The initial concentration of DOX at 13.2 mg/kg could increase the the copies number of fungi significantly(P<0.05). In the degradation process of DOX, the relative abundance of Pseudomonadales, Burkholderiales increased, and that of Bacteroidales, Clostridiales decreased by using the 16 S r DNA method.2. The transmission of the resistance gene tet A, tet W, tet X would be decreased as the initial concentration of DOX were 8.0-13.2mg/kg, and that of tet M would be increased as the initial concentration of DOX were 4.4-10.9mg/kg. The spread of the resistance gene tet G would be decreased as the initial concentration of DOX were 4.4mg/kg. The half-lives of DOX in sterilized treatment were 32.93, 31.17, 26.78, 25.85 days that was significantly longer than that in non-sterilized treatment(12.13, 14.11, 14.88, 14.98days) when the initial concentration of DOX was 4.4mg/kg, 8.0mg/kg, 10.9mg/kg, 13.2mg/kg, respectively. Besides, the degradation half-lives of DOX in the treatment with the initial concentration of 13.2mg/kg was significantly longer than that the4.4mg/kg initial concentration treatment(P<0.05).3. DOX significantly decreased the soil p H, electrical conductivity, total nitrogen and organic carbon(P<0.05). However, there was no significant difference among the groups with different initial concentration of DOX(P>0.05).In summary, DOX could influence the quantity and structure of microorganism. The microorganism also can perform the resistance of DOX and biodegradate of DOX to reduce the negative effect of DOX.