The lipopolysaccharides of Rhodobacter sulfidophilus and the two budding species Rhodopseudomonas acidophila and Rhodopseudomonas blastica were isolated and chemically analyzed. They all have a lipid A backbone structure with glucosamine as the only amino sugar. The lipid A's of Rb. sulfidophilus and Rps. blastica contain phosphate, their fatty acids are characterized by ester-linked, unsubstituted 3-OH-10:0 and amide-linked 3-OH-14:0 (Rb. sulfidophilus) or 3-oxo-14:0 (Rps. blastica). Lipid A of Rps. acidophila is free of phosphate and contains the rare 3-OH-16:0 fatty acid in amide linkage.
The lipopolysaecharides of all three species contain 2keto-3-deoxy-octonate (KDO) but are devoid of heptoses. Neutral sugars with the exception of glucose are lacking in the lipopolysaecharide of Rb. suIfidophilus. This shows a high galaeturonic acid content. The lipopolysaceharides of Rps. acidophila and Rps. blastica have neutral sugar spectra indicative for typical O-chains (rhamnose, mannose, galactose, glucose in both species, and in Rps. blastica additionally 2-O-methyl-6-deoxy-hexose). The taxonomic value of the data is discussed.