Characterization of Cell Wall Peptidoglycan in Enterococcus faecalis Biofilm Using Stable Isotope Labeling by Amino Acids in Cell Culture

The formation of bacterial biofilms is a significant concern in healthcare settings. In an effort to expand the current body of knowledge about biofilm and provide information useful for clinical treatment, this study aims to characterize the chemical composition of the cell wall peptidoglycan of Enterococcus faecalis by liquid chromatography-mass spectrometry (LC-MS). Using Stable Isotope Labeling by Amino Acids in Cell Culture (SILAC), the relative abundance of common cell wall modifications was compared for biofilm and planktonic bacteria. The biofilm phase was found to exhibit decreased O-acetylation, increased N-deacetylation, increased crosslinking, increased carboxypeptidase activity, and increased crosslinker biosynthesis. These findings are consistent with the lower metabolic activity of bacteria in the biofilm phase and the adhesion of biofilm cells to one another and to the hydrophilic components of the biofilm matrix.