EFFECT OF BACTERIAL ASSOCIATION ON THE PHENOTYPE AND GENOTYPE OF AN ENTAMOEBA-HISTOLYTICA CLONAL POPULATION

A several-times-cloned population of Entamoeba histolytica trophozoite s (clone MAVIII) was cultured under axenic (MAVIIIax), monoxenic (MAVI IImx) and polyxenic (MAVIIIpx) conditions. Clones MAVIIIax and MAVIIIm x presented similar virulence in vitro, but differed in their virulenc e in vivo, whereas MAVIIIpx trophozoites were neither virulent in vitr o or in vivo. The MAVIII clones maintained their zymodeme and exhibite d three unusual glucose phosphate isomerase bands, absent in other E. histolytica strains studied, Similar patterns were shown by the three MAVIII clones in the signature of a 482-bp DNA fragment from the M17 g ene (which encodes for a variable immunodominant antigen), obtained by low stringency single specific primer PCR technique. However, MAVIII clones displayed genotypic variability in the patterns obtained by the random amplified polymorphic DNA technique using total DNA as templat e. Results suggest that monomorphism is kept in certain regions of the genome, mainly in those carrying protein encoding genes, but a high p olymorphism is present in total DNA of cloned trophozoites cultured un der different conditions, confirming the plasticity of the E. histolyt ica genome.