The resolution of bacteroides lipopolysaccharides by polyacrylamide gel electrophoresis

The lipopolysaccharides (LPS) of the 10 species of the genus Bacteroides (sensu stricto) were extracted by the proteinase K method and their resolution compared by several methods of polyacrylamide gel electrophoresis (PAGE). These included sodium dodecyl sulphate (SDS)-PAGE with and without urea, polyacrylamide gradient gels and Tricine [N-Tris (hydroxymethyl) methyl glycine]-SDS-PAGE. The original discontinuous system showed good resolution of LPS from B. thetaiotaomicron, B. caccae and B. ovatus and this was enhanced by urea; B. vulgatus showed a typical ladder pattern associated with repeating polysaccharide units of the O side chains. The LPS profiles of the other species, including B. fragilis, were poorly resolved; the majority of components migrated with the leading edge of the wave front. The resolution of the LPS of these species was marginally improved with gradient gels but the majority of components were separated only within the regions of high polyacrylamide concentration. The Tricine-SDS system was consistently superior to the other methods, with excellent resolution of the LPS profiles of all Bacteroides species.