Lipopolysaccharide of Rhodocyclus purpureus: Taxonomic Implication

Abstract

The lipopolysaccharide (O-antigen) of the phototrophic bacterium Rhodocyclus purpureus Ames 6770T was isolated and chemically analyzed. Like the lipid A moiety of Rhodospirillum tenue lipopolysaccharide, the lipid A moiety of Rhodocyclus purpureus lipopolysaccharide contains arabinose, 4-amino-arabinose, glu-cosamine, glucosamine phosphate, and fatty acids. In addition, the fatty acid spectrum, which is comprised of β-C10OH, C14, and C16, is identical to the fatty acid spectrum of Rhodospirillum tenue lipid A. The polysaccharide moiety (degraded polysaccharide) of Rhodocyclus purpureus lipopolysaccharide contains rhamnose, mannose, glucose, galactosamine, and d-glycero-d-mannoheptose in addition to l-glycero-d-mannoheptose and 2-keto-3-deoxyoctonate. The data on lipopolysaccharide composition indicate that the taxonomic relationship between Rhodocyclus purpureus and Rhodospirillum tenue is closer than the relationship between Rhodocyclus purpureus and Rhodopseudomonas gelatinosa.