Characterization of Ssc, an -acetylgalactosamine-containing surface polysaccharide.

Unlabelled: Whole genome sequencing has revealed that the genome of possesses an uncharacterized 5-gene operon (SAOUHSC_00088-00092 in strain 8325 genome) that encodes factors with functions related to polysaccharide biosynthesis and export, indicating the existence of a new extracellular polysaccharide species. We designate this locus as for staphylococcal surface carbohydrate. We found that the genes were weakly expressed and highly repressed by the global regulator MgrA. To characterize Ssc, Ssc was heterologously expressed in and extracted by heat treatment. Ssc was also conjugated to AcrA from in using protein glycan coupling technology (PGCT). Analysis of the heat-extracted Ssc and the purified Ssc-AcrA glycoconjugate by tandem mass spectrometry revealed that Ssc is likely a polymer consisting of -acetylgalactosamine. We further demonstrated that the expression of the genes in affected phage adsorption and susceptibility, suggesting that Ssc is surface-exposed.

Importance: Surface polysaccharides play crucial roles in the biology and virulence of bacterial pathogens. produces four major types of polysaccharides that have been well-characterized. In this study, we identified a new surface polysaccharide containing N-acetylgalactosamine (GalNAc). This marks the first report of GalNAc-containing polysaccharide in . Our discovery lays the groundwork for further investigations into the chemical structure, surface location, and role in pathogenesis of this new polysaccharide.