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Lipopolysaccharides of the cyanobacterium Microcystis aeruginosa
Abstract:
Lipopolysaccharides (LPS) of two isolates of Microcystis aeruginosa were extracted with phenol/water and purified. Cesium chloride gradient ultracentrifugation of these preparations yielded only one fraction. The LPS contained significant amounts of 3-deoxy-D-manno-octulosonic acid, glucose, 3-deoxy sugars, glucosamine, fatty acids, fatty acid esters, hexoses, and phosphate. Heptose, a characteristic sugar component of the polysaccharide moiety of LPS of most gram-negative bacteria was absent. Lipopolysaccharides and lipid A hydrolysate of LPS preparations were active in mouse lethality and Limulus lysate gelation. The lipid A moiety was slightly less active in toxicity and Limulus lysate gelation assays than the intact LPS. The LPS and lipid A moiety of the two isolates of M. aeruginosa were less active in toxicity in mice and Limulus test than LPS of Salmonella abortus equi.
Insights
This study characterized lipopolysaccharides (LPS) from Microcystis aeruginosa, finding they induced toxicity and Limulus gelation. The LPS lacked heptose but contained other typical components, with lipid A being less active than intact LPS.
Area of Science:
- Microbiology
- Biochemistry
- Toxicology
Background:
- Microcystis aeruginosa is a cyanobacterium known for producing toxins.
- Lipopolysaccharides (LPS) are critical components of Gram-negative bacterial outer membranes, often exhibiting endotoxic properties.
Purpose of the Study:
- To extract and characterize the lipopolysaccharides (LPS) from two Microcystis aeruginosa isolates.
- To assess the biological activity, specifically toxicity and Limulus lysate gelation, of the extracted LPS and its lipid A component.
Main Methods:
- Phenol/water extraction and purification of LPS.
- Cesium chloride gradient ultracentrifugation for LPS fractionation.
- Chemical analysis of LPS composition (sugars, fatty acids, phosphate).
- Mouse lethality assays and Limulus lysate gelation tests to evaluate biological activity.
Main Results:
- LPS from M. aeruginosa isolates were successfully extracted and purified into a single fraction.
- The LPS contained 3-deoxy-D-manno-octulosonic acid, glucose, glucosamine, fatty acids, and phosphate, but notably lacked heptose.
- Both LPS and its lipid A hydrolysate demonstrated activity in mouse lethality and Limulus lysate gelation assays.
- The lipid A moiety showed slightly reduced activity compared to intact LPS.
- Toxicity and Limulus activity of M. aeruginosa LPS were lower than that of Salmonella abortus equi LPS.
Conclusions:
- The LPS from M. aeruginosa possesses endotoxic properties, indicated by mouse lethality and Limulus assay activity.
- The absence of heptose in M. aeruginosa LPS distinguishes it from typical Gram-negative bacterial LPS.
- The lipid A component is crucial for the observed biological activities, though intact LPS may be more potent.