INTRASPECIFIC VARIATION AND PHYLOGENETIC-RELATIONSHIPS IN THE GENUS ENTAMOEBA AS REVEALED BY RIBOPRINTING

Eighty-seven isolates of amebae assigned to the genus Entamoeba have b een studied by riboprinting (restriction enzyme polymorphism analysis of polymerase chain reaction amplified small subunit ribosomal RNA gen es). Twenty-four distinct patterns were obtained, roost of which corre sponded to previously described species. In three species (Entamoeba c oli, Entamoeba gingivalis and Entamoeba moshkovskii) intraspecific var iation was detected that led to the grouping of isolates into `ribodem es' (populations of amebae that share the same riboprint pattern). The riboprint data were used to estimate genetic distances among and with in species for the construction of phylogenetic trees based on parsimo ny and distance analysts. The trees obtained with the two methods are largely congruent. In some cases the estimated distances between speci es were greater than the upper limit recommended for the fragment comi gration method of analysis indicating unusually deep branches within t his genus. However, it appears that those species producing cysts with eight nuclei, those producing cysts with one nucleus, and those produ cing cysts with four nuclei form morphologically based groups that are supported by the riboprint data. The oral parasite Entamoeba gingival is, which does not encyst, clusters with the third group indicating se condary loss of this ability.