Role of Pseudomonas aeruginosa biofilm in the initial adhesion, growth and detachment of Escherichia coli in porous media

This study systematically investigated the impact of Pseudomonas aeruginosa biofilm on the initial adhesion, growth, and detachment of indicator bacteria Escherichia coli JM109 in porous media. Two P. aeruginosa strains, the mucoid PDO300 and wide type PAO1 with different extracellular polymeric substance (EPS) composition and secretion capability, were used to grow biofilm in packed beds. Results from the column breakthrough curves and retained JM109 profiles show that the amount and composition of P. aeruginosa biofilm EPS have a profound impact on the deposition and retention of E. coli in porous media. PAO1 biofilm coating improved E. coli retention in the column, whereas PDO300 biofilm coating had only a small impact on E. coli removal. Biofilm surface hydrophobicity and polymeric interactions between the biofilm and E. coli cell surfaces were found to play important roles in controlling the distribution of E. coli along the columns. After initial attachment, E. coli bacteria were able to survive and grow at similar growth rates in columns coated with either PAO1 or PDO300 biofilms with a relatively low nutrient supply. Biofilm detachment was the major mechanism that introduced E. coli bacteria to the bulk fluid long after the contamination event when E. coli cells became an integral part of the biofilm. Findings of this study suggest that biofilm plays a significant role in controlling the initial attachment, growth, and survival of bacteria in porous media, and that the interaction between bacteria and biofilm surfaces should be considered when predicting bacterial and pathogen migration in the environment.