Inhibitory Effects of d -Amino Acids on Staphylococcus aureus Biofilm Development

Abstract

ABSTRACT Biofilms are communities of cells held together by a self-produced extracellular matrix typically consisting of protein, exopolysaccharide, and often DNA. A natural signal for biofilm disassembly in Bacillus subtilis is certain d -amino acids, which are incorporated into the peptidoglycan and trigger the release of the protein component of the matrix. d -Amino acids also prevent biofilm formation by the related Gram-positive bacterium Staphylococcus aureus . Here we employed fluorescence microscopy and confocal laser scanning microscopy to investigate how d -amino acids prevent biofilm formation by S. aureus . We report that biofilm formation takes place in two stages, initial attachment to surfaces, resulting in small foci, and the subsequent growth of the foci into large aggregates. d -Amino acids did not prevent the initial surface attachment of cells but blocked the subsequent growth of the foci into larger assemblies of cells. Using protein- and polysaccharide-specific stains, we have shown that d -amino acids inhibited the accumulation of the protein component of the matrix but had little effect on exopolysaccharide production and localization within the biofilm. We conclude that d -amino acids act in an analogous manner to prevent biofilm development in B. subtilis and S. aureus . Finally, to investigate the potential utility of d -amino acids in preventing device-related infections, we have shown that surfaces impregnated with d -amino acids were effective in preventing biofilm growth.