Effects of chicken manure organic fertilizer on antibiotic resistance genes and integrase genes in soil
In order to investigate the effects of the application of chicken manure organic fertilizer on the distribution of antibiotic resistance genes and integrase genes in soil and their correlations with environmental factors, high-throughput PCR was used to monitor the variations of tetracycline resistance genes, macrolactone resistance genes and integrase genes in soil, as well as the soil physicochemical properties, after 120 d of chicken manure organic fertilizer application. The results showed that the electrical conductivity (EC), pH, and organic matter contents of manure applied soil increased, while oxidation-reduction potential (ORP) decreased from 217.27 mV to 154.47 mV. The contents of nitrogen, phosphorus, potassium, Cu, Zn, and Pb increased in soil. The relative abundances of five types of tetracycline resistance genes: tetM, tetQ, tetW, tetG and tetX, increased by 2.90, 0.97, 6.80, 0.98 and 0.94 times after 120 d of fertilization, respectively. The abundances of five types of macrolactone resistance genes: erm35, ermB, ermT, ermX, and ermF, increased by 0.98, 136.68, 0.95, 2.89 and 2.89 times, but the abundance of erm36 decreased by 0.75 times, of which the highest abundance of ermB and the lowest one of erm36 occurred in the fertilized soils. After application of chicken manure organic fertilizer, the relative abundances of intI1 and intI3 in soil decreased by 4.71 × 10-5 and 2.57 × 10-7, respectively, while the relative abundance of intI2 increased by 3.74 × 10-6. Network analysis showed that intI3 was negatively correlated with the genes except for ermB (R=-1.00, P < 0.05).