Characteristic biological activities of lipopolysaccharides from Sinorhizobium and Mesorhizobium

The biological actions of lipopolysaccharides (LPSs) from Sinorhizobium meliloti, Mesorhizobium loti and Escherichia coli were compared. In biological activities including lethality, production of tumor necrosis factor (TNF)-α and nitric oxide (NO), adjuvant action and Limulus activity, LPS from S. meliloti exhibited stronger actions than LPS from M. loti, but had a weaker action than LPS from E. coli. On the other hand, M. loti LPS showed a higher activity to activate human complement than S. meliloti LPS. Further, there was a significant difference in polymyxin B binding between S. meliloti LPS and M. loti LPS, suggesting a difference in the lipid A structure. LPSs from S. meliloti and M. loti seem to exhibit characteristic biological actions that may be dependent on the difference in the lipid A structure.