Biodegradation of antibiotic ciprofloxacin: pathways, influential factors, and bacterial community structure.

Antibiotic ciprofloxacin is ubiquitous in the environment. However, little is known about ciprofloxacin dissipation by microbial community. The present study investigated the biodegradation potential of ciprofloxacin by mixed culture and the influential factors and depicted the structure of ciprofloxacin-degrading microbial community. Both the original microbiota from drinking water biofilter and the microbiota previously acclimated to high levels of ciprofloxacin could utilize ciprofloxacin as sole carbon and nitrogen sources, while the acclimated microbiota had a much stronger removal capacity. Temperature rise and the presence of carbon or nitrogen sources favored ciprofloxacin biodegradation. Many novel biotransformation products were identified, and four different metabolic pathways for ciprofloxacin were proposed. Bacterial community structure illustrated a profound shift with ciprofloxacin biodegradation. The ciprofloxacin-degrading bacterial community was mainly composed of classes Gammaproteobacteria, Bacteroidia, and Betaproteobacteria. Microorganisms from genera Pseudoxanthomonas, Stenotrophomonas, Phenylobacterium, and Leucobacter might have links with the dissipation of ciprofloxacin. This work can provide some new insights towards ciprofloxacin biodegradation.