Ultrastructure of Klebsiella O3 lipopolysaccharide isolated from culture supernatant: structure of various uniform salt forms

Abstract

Various uniform salt forms of Klebsiella O3 lipopolysaccharide (KO3 LPS) isolated from culture supernatant were prepared as follows. Basic materials present in KO3 LPS were rigorously removed by electrodialysis and the electrodialyzed KO3 LPS was neutralized with NaOH, KOH, NH4OH, Ca(OH)2, tris(hydroxymethyl)aminomethane, or triethylamine. The ultrastructure of the uniform salt forms of KO3 LPS was examined using preparations stained with uranyl acetate. The sodium, potassium, ammonium, and trisaminomethane salt forms were structurally very similar to the natural form of KO3 LPS which consisted of a mixture of flat ribbon-like structures (average width of 16 nm and average thickness of 7 nm) and spheres with various diameters, both covered with fine hairy structures. When KO3 LPS was converted to the triethylamine salt form, the ribbon-like structures were disrupted into very small granules (7-9 nm X 9-15 nm). The calcium salt form consisted of particles and rods of various sizes and ribbon-like structures which were markedly extended (maximum width of 50 nm) and presented irregular shapes. When converted to the calcium salt form, the ribbon-like structures were extended and eventually divided into particles and rods. For reasons still unknown, the sodium salt of KO3 LPS was mostly stained positively with uranyl acetate in contrast to the natural form and the other uniform salt forms which were always negatively stained. In the positively stained preparation of the sodium salt form, it was clearly shown that the ribbon-like structures consisted of a bilayer.