Mildly Inhibitory Effects of Sodium Polyanethol Sulfonate and pH on the Growth of Wildtype, lrgAB, and cidAB Mutants of Streptococcus mutans

Abstract

The lrgAB and cidAB operon encodes for anti-holin-like proteins and holin-like proteins respectively, which are mechanisms of control for endolysin activity in S. mutans. The upregulation of lrgAB genes by chitosan is purported to cause increased cell lysis in Streptococcus mutans by promoting the action of extracellular murein hydrolases. These enzymes can be inhibited by polyanethol sulfonate (SPS). This study tested whether SPS at the pH levels needed to dissolve chitosan is inhibitory to S. mutans. By testing the effects of pH and SPS separate from chitosan in lrgAB, cidAB, and wild-type S. mutans, we can test whether the reagents are suitable to use in assessing the effects of chitosan on the genes. A turbidity assay was used to monitor the growth of wild-type, cidAB, and lrgAB mutants in SPS and non-SPS treated Todd-Hewitt broth over a 75 minute period at pH 5, 6, and 7.2. Results showed that 0.5% SPS was capable of slowing the growth of all strains at pH 6 and 7.2, with the greatest effect on lrg AB mutants and the least obvious effect on cid AB mutants. Cell growth for all strains was generally arrested at pH 5 regardless of the presence of SPS. Because SPS showed inhibitory effects on growth by itself, its use in chitosan studies as an inhibitor of endolysin is questionable.