In vivo determination of Neisseria meningitidis serogroup A capsular polysaccharide by whole cell high-resolution magic angle spinning NMR spectroscopy

High resolution-magic angle spinning (HRMAS) NMR spectroscopy was applied to serogroup A Neisseria meningitidis (NMA) to determine precise structures of capsular polysaccharide (CPS) expressed on the meningococcal surface. Both the O-acetylated (OAc) NMA parent and a mynC::aphA3 OAc− mutant demonstrated characteristic CPS-derived NMR signals indicating cell-surface expression of CPS, but only the parent expressed O-3 and O-4 acetylation signals. A capsule-defective strain showed no NMR signals for CPS. The 1H NMR HRMAS spectral patterns correlated with the purified CPS 1H NMR profiles. HRMAS NMR can distinguish detailed complex carbohydrate structures expressed on bacteria. NMA express both O-3 and O-4 acetylated polymers but not in equimolar ratio amounts in vivo.