Validation and redescription of Acanthamoeba terricola Pussard, 1964 (Amoebozoa: Acanthamoebidae)

Acanthamoeba castellanii (Douglas, 1930) Page, 1967 is the type species of a widespread genus of free-living amoebae, potentially pathogenic for humans and animals. The Neff strain is one of the most widely used in biological research, serving as a model for both A. castellanii and the whole genus in general. The Neff strain, isolated in California, closely resembles another strain found in France and originally described as a separate species, Acanthamoeba terricola Pussard, 1964, but both were successively synonymized with A. castellanii. Molecular sequence analysis has largely replaced morphological diagnosis for species identification in Acanthamoeba, and rDNA phylogenies show that the Neff strain forms a distinct lineage from that of the type strain of A. castellanii. In this study, we compared the type strain of A. terricola with the Neff strain and A. castellanii, and analysed the available molecular data including new sequences obtained from A. terricola. Here we provide molecular evidence to validate the species A. terricola. The Neff strain is therefore transferred to A. terricola and should no longer be considered as belonging to A. castellanii.