Enterococcus faecalis OG1RF is a rifampin and fusidic acid resistant strain of E. faecalis OG1, a strain isolated from patients with root canal infections. E. faecalis poses significant threat in clinical environments due to its antibiotic resistance characters, pathogenicity, and ability to endure stress. In hospital infections, E. faecalis generally form biofilms, which alters its biochemistry compared to planktonic cells. To test the impact of pH stress on E. faecalis OG1RF biofilm growth, bacterial biofilms were grown in acidic (pH 4.8), neutral (pH 7.0), and basic (pH 9.0) conditions using bead transfer method. After 4 consecutive serial cultures, strains from the high pH condition showed two size differentiated phenotypes. In 22-hour growth curves, all the small colony variants (SCV) outgrew the normal colonies, including the ancestor, at high pH. However, the SCVs grew slower compared to the other colonies at low pH and had similar growth at neutral pH. A DNA analysis showed that each SCV had one unique mutation, either in the pyrR, pstB, or pstC gene, while the other colonies did not have a single mutation.
Wadud, Ayman and Slonczewski, Joan, "The Effect of pH Stress on E. faecalis OG1RF Biofilm Formation" (2022). Kenyon Summer Science Scholars Program. Paper 598.