CATIONIC INTERACTIONS IN THE LIPOPOLYSACCHARIDE OF DESULFOVIBRIO-VULGARIS

High performance liquid chromatography (HPLC), energy-dispersive X-ray analysis and sodium dodecyl sulphate-polyacrilamide gel electrophores is (SDS-PAGE) were used to investigate the interactions between variou s cations and the lipopolysaccharide (LPS) of Desulfovibrio vulgaris. The LPS was shown to have different affinities for various divalent io ns. Electrodialysis removed a substantial amount of the iron(II) ions bound to LPS and caused an increase in calcium ions. Differences in th e structure of LPS isolated from iron-rich and iron-poor cells demonst rated by HPLC and SDS-PAGE analyses indicated that iron(II) may have a role in stabilising sugar residues in the LPS molecule. This role is specific to iron (II), since increased calcium levels in iron-poor LPS do not maintain the structure. Sodium and potassium ions, however, ap peared to be interchangeable in their binding to LPS. The results prov ide additional evidence for the suggested role of D. vulgaris LPS in t he uptake of iron(II) from the environment.