title: Biodegradation of the veterinary antibiotics enrofloxacin and ceftiofur and associated microbial community dynamics.
abstract: Fluoroquinolones and cephalosporins are two classes of veterinary antibiotics arising as pollutants of emerging concern. In this work, the microbial degradation of two representative antibiotics of both these classes, enrofloxacin (ENR) and ceftiofur (CEF), is reported. Biodegradation of the target antibiotics was investigated by supplementing the culture medium with ENR and CEF, individually and in mixture. Microbial inocula were obtained from rhizosphere sediments of plants derived from experimental constructed wetlands designed for the treatment of livestock wastewaters contaminated with trace amounts of these antibiotics. Selected microbial inocula were acclimated during a period of 5months, where the antibiotics were supplemented every three weeks at the concentration of 1mgL-1, using acetate as a co-substrate. After this period, the acclimated consortia were investigated for their capacity to biodegrade 2 and 3mgL-1of ENR and CEF. Complete removal of CEF from the inoculated culture medium was always observed within 21days, independently of its concentration or the concomitant presence of ENR. Biodegradation of ENR decreased with the increase in its concentration in the culture medium, with defluorination percentages decreasing from ca. 65 to 4%. Ciprofloxacin and norfloxacin were detected as biodegradation intermediates of ENR in the microbial cultures supplemented with this antibiotic, indicating that defluorination of at least part of ENR in these cultures is not an immediate catabolic step. Abiotic mechanisms showed high influence in the removal of CEF, affecting less ENR degradation. The acclimation process with the target antibiotics led to significant shifts in the structure and diversity of the microbial communities, predominantly selecting microorganisms belonging to the phyla Proteobacteria (e.g. Achromobacter, Variovorax and Stenotrophomonas genera) and Bacteroidetes (e.g. Dysgonomonas, Flavobacterium and Chryseobacterium genera). The results presented in this study indicate that biodegradation can be an important mechanism for the environmental removal of the tested compounds.
authors.affiliation: Interdisciplinary Centre of Marine and Environmental Research, University of Porto, Terminal de Cruzeiros do Porto de Leixões, Avenida General Norton de Matos s/n, 4450-208 Matosinhos, Portugal; Institute of Biomedical Sciences Abel Salazar, University of Porto, Rua de Jorge Viterbo Ferreira 228, 4050-313 Porto, Portugal; Faculty of Sciences, University of Porto, Rua do Campo Alegre 790, 4150-171 Porto, Portugal.
authors.forename: Diogo A M
authors.initials: DAM
authors.lastname: Alexandrino
authors.affiliation: Interdisciplinary Centre of Marine and Environmental Research, University of Porto, Terminal de Cruzeiros do Porto de Leixões, Avenida General Norton de Matos s/n, 4450-208 Matosinhos, Portugal.
authors.forename: Ana P
authors.initials: AP
authors.lastname: Mucha
authors.affiliation: Interdisciplinary Centre of Marine and Environmental Research, University of Porto, Terminal de Cruzeiros do Porto de Leixões, Avenida General Norton de Matos s/n, 4450-208 Matosinhos, Portugal.
authors.forename: C Marisa R
authors.initials: CMR
authors.lastname: Almeida
authors.affiliation: State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008, Jiangsu Province, China.
authors.forename: Wei
authors.initials: W
authors.lastname: Gao
authors.affiliation: State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008, Jiangsu Province, China.
authors.forename: Zhongjun
authors.initials: Z
authors.lastname: Jia
authors.affiliation: Interdisciplinary Centre of Marine and Environmental Research, University of Porto, Terminal de Cruzeiros do Porto de Leixões, Avenida General Norton de Matos s/n, 4450-208 Matosinhos, Portugal. Electronic address: mcarvalho@ciimar.up.pt.
authors.forename: Maria F
authors.initials: MF
authors.lastname: Carvalho
mesh_terms: D000900:Anti-Bacterial Agents / Q000032:analysis*; D001673:Biodegradation, Environmental; D002511:Cephalosporins / Q000032:analysis*; D000077422:Enrofloxacin; D004784:Environmental Monitoring; D024841:Fluoroquinolones / Q000032:analysis*; D014871:Water Microbiology; D014874:Water Pollutants, Chemical / Q000032:analysis*; D053833:Wetlands
chemical_list: D000900:Anti-Bacterial Agents; D002511:Cephalosporins; D024841:Fluoroquinolones; D014874:Water Pollutants, Chemical; D000077422:Enrofloxacin; C053503:ceftiofur
keywords: Biodegradation; Ceftiofur; Enrofloxacin; Metagenomics; Microbial communities