Learning from the rDNA Operon: A Reanalysis of the Acanthamoeba palestinensis Group

The molecular classification of Acanthamoeba is currently based on the analysis of 18S rDNA sequences, delimiting around twenty genotypes (T1-T23). In some cases, however, the resolution of 18S is limited, and other genetic markers could be useful for unravelling poorly resolved lineages. In this study, the partial large subunit (LSU) of rDNA and ITS were used to re-examine the Acanthamoeba palestinensis group (T2/T6 lineage), which consists of various poorly defined lineages, including the T2 and T6 genotypes. New sequences overlapping 18S, ITS, and LSU were recovered. The analysis placed previously identified partial ITS-LSU sequences as T2/T6 and further confirmed the separation of the OX1 lineage from T2. In addition, analysis of the second internal transcribed spacer (ITS-2) suggests that multiple species may be present within the T6 and OX1 lineages. The results obtained from the T2/T6 lineage analysis confirm the utility of partial LSU and ITS for the study of Acanthamoeba, suggesting their advantage for disentangling complex lineages.