title: Solubility of endotoxins from Escherichia coli and Pseudomonas aeruginosa.
abstract: BACKGROUND
  The Limulus amebocyte lysate (LAL) assay may underestimate endotoxins because only soluble endotoxins are determined. The solubility of endotoxins was, therefore, studied in two species of Gram-negative bacteria.
  
  
  METHODS
  Cultures were grown in serum broth, cells were harvested by centrifugation and washed in physiological saline. Bacterial suspensions were either filtered through PTFE filters and air dried at room temperature, dried in polypropylene tubes at room temperature in a desiccator, or freeze dried. Samples were extracted with aqueous Tween 20. The soluble and insoluble fractions were dried, methanolysed, and hydroxy-fatty acid methyl esters were determined by gas chromatography (GC) as markers of endotoxins.
  
  
  RESULTS
  The solubility of the endotoxins from Escherichia coli and Pseudomonas aeruginosa ranged from 9% to 83%. Species and drying conditions had substantial influence on the solubility.
  
  
  CONCLUSIONS
  Endotoxin exposure may be underestimated in environmental samples by the LAL test because a substantial fraction can be non-soluble and is not detected.
authors.affiliation: National Institute of Occupational Health, Oslo, Norway. Winjaud.Eduard@stami.no
authors.forename: Wijnand
authors.initials: W
authors.lastname: Eduard
authors.forename: Mette Haraldsen
authors.initials: MH
authors.lastname: Westby
authors.forename: Lennart
authors.initials: L
authors.lastname: Larsson
mesh_terms: D001427:Bacterial Toxins / Q000032:analysis* / Q000302:isolation & purification; D002849:Chromatography, Gas; D004731:Endotoxins / Q000032:analysis* / Q000302:isolation & purification; D004926:Escherichia coli / Q000737:chemistry*; D005227:Fatty Acids / Q000737:chemistry; D011550:Pseudomonas aeruginosa / Q000737:chemistry*; D012995:Solubility
chemical_list: D001427:Bacterial Toxins; D004731:Endotoxins; D005227:Fatty Acids