Biodegradation of antibiotics by denitrification and their effects on the physiology, kinetics, and denitrifying microbial communities

Abstract

Background. Water pollution by nitrate and antibiotics has been growing over the years, so the denitrifying process can be a good alternative for the simultaneous removal of both compounds. Objective. Show the role of denitrification in the elimination of antibiotics, as well as their effects on the physiology and kinetics of the respiratory process, genes, and denitrifying microbial populations. Results. There are studies on the elimination of different antibiotics under denitrifying conditions, however, in most of them, the fate of the carbonated and nitrogenous matter consumed is unknown. Antibiotics such as sulfonamides and tetracyclines cause negative effects on the denitrifying process by decreasing the nitrate removal efficiency, its rate of consumption, and promoting the accumulation of nitrite. Denitrifying genera such as Thauera and Pseudomonas were reported as resistant and/or tolerant to the presence of different antibiotics belonging to fluoroquinolones, macrolides, tetracyclines, and β-lactams, as well as mixtures of antibiotics. Decreased abundance and gene expression of genes involved in denitrification such as nirS and nosZ, was observed in the presence of sulfonamides, this effect could cause nitrite and nitrous oxide accumulation, producing a possible bottleneck in the denitrifying process. Antibiotic resistance genes have been detected in denitrifying microorganisms exposed to antibiotics, which could act as defense mechanisms to the presence of these compounds. Conclusions. The information contained in this review contributes to the knowledge about the denitrifying process and proposes its use to carry out more efficient and stable disposal of nitrate and antibiotics present in contaminated waters.