Resumen
- Aim: Although feed medicated with antibiotics is widely used in animalproduction to prevent and treat bacterial infections, the effect of these drugson nontarget anaerobic bacteria is unknown. We aimed to clarify whether asingle exposure of sulphate-reducing bacteria (SRB) from a tilapia pond tooxytetracycline (OTC) concentrations relevant to aquaculture impacts theirfunction, abundance and community structure.Methods and Results: To demonstrate changes in SO42content, SRBabundance, dsrB copy number and SRB diversity, sediment mesocosms werespiked with 5, 25, 50 and 75 mg OTC kg1and examined for 30 days bymeans of ion chromatography, qPCR, cultivation and fluorescent in situhybridization (FISH). On day 3, we measured higher SO42concentrations(ca. two-fold) and a reduction in dsrB copy numbers of approximately 50% inthe treatments compared to the controls. After 30 days, a subtle yet measurableenrichment of bacteria from the order Desulfovibrionales occurred inmesocosms receiving ≥50 mg OTC kg1, notwithstanding that SRB countsdecreased two orders of magnitude. OTC was dynamically and reversiblyconverted into 4-epioxytetracycline and other related compounds in a dose-dependent manner during the experiment.Conclusions: A single exposure to rather high OTC concentrations triggeredfunctional and structural changes in a SRB community that manifested quicklyand persisted for a month.Significance and Impact of the Study: This study improves our limitedknowledge on the ecotoxicology of antibiotics in anaerobic environments.