Schemes for the serological typing of Pseudomonas cepacia by its heat-stable (0) antigens have been developed1-3 in order to assist in the epidemiological monitoring of clinical isolates of this opportunistic pathogen. The results of recent structural studies by Knirel and co-workers4-ia and ourselvesltJZ on the putative 0 antigens of P. cepacia are providing a chemical basis for the serological classification and relationships. We have used the reference strains selected by Heidt et all, and have produced structures for the 01 (ref. 12), 03 (ref. ll), and 05 (ref. 11) polymers. Now we present results for a polymer from the reference strain (A.T.C.C. 17759) for serogroup 07.
Neutral sugar components of the lipopolysaccharide were glucose, mannose, rhamnose, and aldoheptoses (mainly L-glycero-D-manno-heptose or its enantiomer, with a smaller proportion of D-glycero-D-manno-heptose or its enantiomer). Mild acid hydrolysis of the lipopolysaccharide in the presence of sodium dodecyl sulphaten apparently did not release lipid A completely: the major polymeric fraction (yield, 24%) eluted from Sephadex G-50 was preceded by phosphorus-containing carbohydrate (16%), assumed to be undegraded lipopolysaccharide (phosphorus being a characteristic component of lipid A, and often of the core oligosaccharide). Incomplete release of lipid A by the method used here has also been observed with the lipopolysaccharide from P. cepacia serogroup 03 (ref. 11). In addition to the polymeric fractions, water-soluble products in the 07 hydrolysate included oligomeric material expected to be derived from lipopolysaccharide lacking the O-specific chain. The core oligosaccharide is likely to be the source of the aldoheptoses and also of the rhamnose detected (rhamnose is a minor component of several lipopolysaccharides from P. cepacia14J5, and the core oligosaccharide from strain N.C.T.C. 10661, which is apparently equivalent to A.T.C.C. 17759, contains a rhamnopyranosyl group16).
Structural studies were confined to the major polymeric 07 fraction, which consisted mainly of D-glucose (40%) and D-mannose (36%). The 'H-n.m.r, spectrum of the polymer contained three major signals (each 1 H) in the anomeric