LIPOPOLYSACCHARIDE AND PORIN OF ROSEOBACTER-DENITRIFICANS, CONFIRMINGITS PHYLOGENETIC RELATIONSHIP TO THE ALPHA-3 SUBGROUP OF PROTEOBACTERIA

Roseobacter denitrificans has rough (R)-type lipopolysaccharide, conta ining 2-keto-3-deoxyoctonate but no heptoses. Its lipid A has a glucos amine-containing, phosphorylated backbone. It contains the rare 3-oxot etradecanoic (3-oxomyristic) acid as the only amide-bound fatty acid a nd ester-bound 3-hydroxydecanoic acid, this pattern being characterist ic for the alpha-3 subgroup of Proteobacteria. Treatment of the major outer-membrane protein (porin, apparent molecular mass 88 kDa) of Rose obacter denitrificans with EDTA (2 mM, 30 degrees C, 20 min) resulted in the dissociation of the oligomers into monomers (apparent molecular mass 35 kDa). EDTA-sensitive dissociation has so far been observed on ly within the alpha-3 subgroup of Proteobacteria. The 12 N-terminal am ino acids of the monomers exhibit sequence homology with the porins of Rhodobacter capsulatus, Rhodobacter sphaeroides and Rhodopseudomonas blastica. Renaming of Roseobacter denitrificans as Rhodobacter denitri ficans is suggested.