Impact of Chlorine Disinfection on Redistribution of Cell Clusters from Biofilms

Detachment and redistribution are essential stages in the biofilm life cycle; however they are the least studied, especially in the presence of disinfectant. In this study, three Pseudomonas aeruginosa strains (wild-type, alginate-deficient mutant, and alginate-overproducing mutant) were used to cultivate three single strain biofilms in flowcell systems. Both physiochemical and biological properties of cells detached from different growth stages of biofilm and their ability to reattach on new surfaces were analyzed and compared. The presence of chlorine influenced bacterial surface functional groups and further prevented the transition from reversible to irreversible attachment by interrupting hydrogen bonding, polymeric interaction and hydrophobic interaction. Even though chlorine inhibited bacterial attachment, the detached clusters from all tested strains were still able to survive and immobilize themselves downstream, forming viable new biofilms. Furthermore, alginate EPS production increased the size and surface charge of detached clusters as well as their resistance to chlorine disinfection. The redistributed biofilms of alginate-producing strains had a higher amount of total biomass, greater biofilm thickness, and more complex structural properties (both with and without chlorine conditions) and elevated viability (95% viable ratio) in the presence of chlorine when compared to the alginate-deficient strain (54% viable ratio).