Auxotrophy to lipoproteins of Entamoeba histolytica cultivated under axenic conditions

Entamoeba histolytica grows in media without serum but with a mixture of am inoacids, vitamins, lipoproteins, free cholesterol, phospholipids and fatty acids called PACSR. The ability of lipoproteins and free lipids to support growth of three E. histolytica strains (HK9, HMI:IMSS and HM3:IMSS) was an alysed. Tubes containing 5 ml culture medium, amino acids, vitamins and eit her 120-1,200 mug lipoproteins/ml or 0.017-0.10 mg free lipids/ml (predisso lved in absolute ethanol) were inoculated with 1 x 10(4) trophozoites/ml an d incubated at 37 degreesC for 72 h. Amoebae died within 12 h in the presen ce of any free lipid combination, while those having 240-480 mg lipoprotein s/ml reached densities similar to or higher than those of controls (dependi ng on strain). The addition of ethanol (0.1%) to the media produced stable lipid solutions and did not show significant adverse effects. Accordingly, E. histolytica is auxotrophic to lipoproteins and unable to use free choles terol, phospholipids or fatty acids.