Effect of Antibiotics on ferequency of Native Fungi and Bacteria in Soils Treated by Organic and Mineral Conditioners

Nowadays, extensive application of antibiotics in medicine for treating people and in agriculture and veterinary caused soil and water contamination and also have negative impacts on soil microorganisms and biological processes rate. In the present study, the effect of releasing the mostly used antibiotic in soil (gentamicin, oxytetracycline, and penicillin) and different concentrations (50, 100 and 200 mg/kg dry soil) with and without organic and mineral conditioner (cow manure, biochar, and nano-zeolite) on total soil fungi, total cultivable bacteria and coliforms and their resistance and resilience indices at three time periods including 1-7, 7-30 and 30-90 days during a 90-day incubation time was evaluated in a split-factorial design which soil conditioners were considered as main plots and antibiotic types and concentration were as experimental factors. Resistance and resilience indices were calculated for microbial groups, as well. The addition of antibiotics, including gentamicin, reduced the abundance of microorganisms. Based on the results, cow manure had the highest total fungi count at 1-7 days which had no significant difference with biochar application. At 7-30 days, total bacteria count in antibiotic-treated soil significantly increased which the increase rate for gentamicin and oxytetracycline, especially at higher concentrations was more than penicillin. At 7-30 and 30-90 days, the application of cow manure and gentamicin and oxytetracycline at 100 and 200 mg/kg soil resulted in the highest total coliforms count. Generally, the results of the present study showed that the application of conditioners, especially cow manure, could decrease the toxic effects of antibiotics in soils and causes an increase in resistance and resilience indices of soil microorganisms.