Chemical composition of exopolymeric substrate produced by Rothia mucilaginosa

Abstract

Apical periodontitis is a chronic inflammatory disorder of periradicular tissues caused by microorganisms surviving in periapical tissues. We isolated Rothia mucilaginosa from a periapical periodontitis lesion where the presence of bacteria was noted in root canals after numerous treatments. Strain DY-18 was randomly selected from this case for further study. Scanning electron micrographs revealed that strain DY-18 possesses unique phenotypic characteristics, exhibiting dense meshwork-like structures on their cells. The results of staining with Calcofluor, a polysaccharide binding dye, suggested that strain DY-18 produces exopolysaccharide (EPS). Our previous studies suggested that EPS is a major component of bacterial biofilms in the oral cavity. High performance liquid chromatography showed that the EPS purified from culture supernatant contained neutral sugars including galactose, mannose, rhamnose and glucose, and amino sugars including glucosamine and galactosamine, but not uronic acid or extracellular DNA. Additionally, there are some genes relating to galactose and mannose metabolism on the genome of strain DY-18. Our results suggest that strain DY-18 has the ability to form a biofilm containing EPS.