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.