Lipopolysaccharide of the Phototrophic BacteriumRhodospirillum fulvum

Summary Laser desorption mass spectrometry of free lipid A of the phototrophic bacterium Rhodospirillum fulvum revealed a glucosamine disaccharide backbone, where the reducing glucosamine was substituted at C-1 by galacturonic acid (substituted by an unknown compound) and the nonreducing glucosamine at C-4’ by L -glycero- D-manno -heptose. The mass spectra of the liberated acyl-oxyacyl residues showed 3-O-(14:0)-16:0 and 3-O-(16:0)-16:0 as amide-linked and 3-O-(12:0)-14:0 as ester-linked diesters in the lipid A. Lipid A was free of phosphate, as indicated by a colorimetric test and and confirmed by 31 P NMR. The lipopolysaccharide of Rhodospirillum fulvum contained xylose, glucose, glucuronic and galacturonic acids, L -glycero- and D -glycero- D-manno -heptoses as well as 2-keto-3-deoxyoctonate. It had a lethality of about 1/10 from that reported for Salmonella abortus equi lipopolysaccharide and was able to induce TNFα and IL6 in macrophages of endotoxin responder C57BL/10 ScSN-mice.