Abstract:The experiment was aimed to investigate the effects of ENR (enrofloxacin) on microbial community diversity in soil. The molecular diversity of denitrifying bacteria was analyzed by PCR-based cloning and RFLP (restriction fragment length polymorphism) methods. PCR-RFLP analysis revealed that the percentages of OTUs to total clones among groups Ⅰ to Ⅵ (0, 0.01, 0.1, 1, 10μg/g and 50μg/g, respectively) were 48.30%, 41.88%, 34.78%, 33.62%, 25.42% and 23.81%, respectively after the ENR addition for 35 days, and that the percentages were 29.66%, 2424%, 18.10%, 16.67%, 15.83% and 14.39% after the ENR addition for 70 days, respectively. The effects of ENR on diversity of denitrifying bacteria were enhanced with the increasing ENR concentrations. The results showed that the Margalef Index in CK was significantly (P<0.05) higher than those from soils amended with ENR after 35 days. The Margalef Index in CK was only significantly higher than those in soils treated with 10 g/g and 50 g/g of ENR after 70 days, respectively. Shannon-Wiener Indexes in CK were significantly higher than those treated with ENR except 0.01 g/g after 35 days, but the Shannon-Wiener Index in CK was only significantly higher than that in the soils treated with 50 g/g of ENR after 70 days. Our data indicated that the effects of ENR on diversity of denitrifying bacteria in soils at lower concentrations (0.01 g/g to 10 g/g) were decreased with incubation time.