STRUCTURAL ELUCIDATION OF THE LIPOPOLYSACCHARIDE CORE REGION OF THE O-CHAIN-DEFICIENT MUTANT STRAIN A28 FROM PSEUDOMONAS-AERUGINOSA SEROTYPE O6 (INTERNATIONAL ANTIGENIC TYPING SCHEME)

The lipopolysaccharide (LPS) of the Pseudomonas aeruginosa serotype 06 rough-type mutant A28 was isolated by a modified phenol-chloroform-pe troleum ether extraction method, Deoxycholate-polyacrylamide gel elect rophoresis indicated a single band with mobility similar to that of th e complete core region of the wild-type parent serotype 06 (Internatio nal Antigenic Typing Scheme) strain. Compositional analysis of the LPS indicated that the core oligosaccharide was composed of D-glucose (th ree units), L-rhamnose (one unit), 2-amino-2-deoxy-D-galactose (one un it), L-glycero-D-manno-heptose (two units), 3-deoxy-D-manno-octulosoni c acid (two units), L-alanine (one unit), and phosphate (two units). U nder the mild conditions of hydrolysis with methanolic hydrogen chlori de, a 7-O-carbamoyl substituent was observed on the second heptose res idue, The glycan structure of the LPS was determined by employing one- and two-dimensional nuclear magnetic resonance spectroscopy and mass spectrometry-based methods with a backbone oligosaccharide that was ob tained from the LPS by deacylation, dephosphorylation, and reduction o f the terminal glucosamine. On the basis of the results of the present study and our earlier work with the P. aeruginosa 06-derived core-def ective mutant R5 (H. Masoud, E. Altman, J. C. Richards, and J. S. Lam, Biochemistry, 33:10568-10578, 1994), a structural model for the compl ete core oligosaccharide is proposed.