Rapid evolution of RpoS-dependent hyperbiofilm phenotypes in Pseudomonas aeruginosa biofilms under antibiotic stress

In this study, we experimentally evolved P.aeruginosa PAO1 biofilms for cyclic treatment in the presence of high dose of imipenem, and enriched hyperbiofilm mutants with six cycles in two independent lineages. The competition assay showed the evolved hyperbiofilm mutants can outcompete the ancestral strain within biofilm while not planktonic cultures. Whole genome sequencing analysis revealed the hyperbiofilm phenotype is caused by point mutations in rpoS gene in all independently evolved mutants and the same mutation site was found in P. aeruginosa clinical isolates.