A new understanding on the prerequisite of antibiotic biodegradation in wastewater treatment: Adhesive behavior between antibiotic-degrading bacteria and ciprofloxacin

The extensive exploration of antibiotic biodegradation by antibiotic-degrading bacteria in biological wastewater treatment processes has left a notable gap in understanding the behavior of these bacteria when exposed to antibiotics and the initiation of biodegradation processes. This study, therefore, delves into the adhesive behavior of Paraclostridium bifermentans, isolated from a bioreactor treating ciprofloxacin-laden wastewater, towards ciprofloxacin molecules. For the first time, this behavior is observed and characterized through quartz crystal microbalance with dissipation (QCM-D) and atomic force microscopy. The investigation further extends to identify key regulatory factors and mechanisms governing this adhesive behavior through a comparative proteomics analysis. The results reveal the dominance of extracellular proteins, particularly those involved in nucleotide binding, hydrolase, and transferase, in the adhesion process. These proteins play pivotal roles through direct chemical binding and the regulation of signaling molecule. Furthermore, QCM-D measurements provide evidence that transferase-related signaling molecules, especially tyrosine, augment the binding between ciprofloxacin and transferases, resulting in enhance ciprofloxacin removal by P. bifermentans (increased by ∼1.2-fold). This suggests a role for transferase-related signaling molecules in manipulating the adhesive behavior of P. bifermentans towards ciprofloxacin. These findings contribute to a new understanding of the prerequisites for antibiotic biodegradation and offer potential strategies for improving the application of antibiotic-degrading bacteria in the treatment of antibiotics-laden wastewater.