Isolation and characterization of Entamoeba histolytica mutants resistant to emetine

Abstract

Isolation of emetine-resistant mutants of Entamoeba histolytica is described. Spontaneous rate of mutation, obtained from a Luria-Delbrück fluctuation test was 2.5 × 10-7. The mutagenesis frequency obtained from the number of colonies grown in the presence of emetine, divided by the number of viable trophozoites inoculated in semisolid agar was ≤10-7 and it was increased from 10 to 100 fold with ethyl methanesulfonate. Two types of clones were isolated: one was cross-resistant to colchicine and the other was not, indicating that mutation took place at different loci. Protein synthesis in the presence of emetine remained unaltered for colchicine-sensitive mutants, suggesting that the molecular lesion lay in the protein synthesis machinery. Colchicine-resistant mutants showed a lower level of [35S]methionine incorporation, probably due to alterations in the molecular transport of some substances across the membrane. This mutant clone was also deficient in red blood cell adhesion, suggesting membrane alterations. © 1985.