D-Amino acids affect Pseudomonas aeruginosa biofilm and quorum sensing molecules in lung infection models developed under a cystic fibrosis environment

Pseudomonas aeruginosa commonly infects immunocompromised patients, including those with cystic fibrosis (CF). These infections are difficult to treat due to a variety of factors including the ability of Pseudomonas aeruginosa to resist to antibiotic treatment in part due to formation of biofilms. D-amino acids have known biofilm-disruption and antibacterial properties in some bacteria including P. aeruginosa. However, this treatment remains underexplored especially for inhibiting biofilm biomass production under CF environments. We explore the effects of six individual D-amino acids (alanine, aspartic acid, tyrosine, glutamic acid, serine, and proline) on the quorum sensing signaling and biofilm biomass production of two strains: PAO1 and the CF isolate FRD1. The D-amino acid causing the most significant decrease in biofilm mass and a decrease in quorum sensing molecules was D-aspartic acid. Meanwhile D-glutamic acid and D-serine had the opposite effects with an increase in biofilm mass and increase in quorum sensing molecule abundance. D-proline also showed a decrease in quorum sensing signaling with a decrease in biofilm biomass. P. aeruginosa had a lower or delayed quorum sensing response in the presence of D-aspartic acid and the absence of its L- counterpart at 48 h, a potential therapeutic route to explore.