High genetic diversity of Sappinia-like strains (Amoebozoa, Thecamoebidae) revealed by SSU rRNA investigations.

Sappinia diploidea is known as a free-living amoeba of worldwide distribution and has also been reported as causative agent of a brain infection in an immunocompetent young man. In the current study, we were able to isolate eight strains of S. diploidea-like amoebae identified by light microscopy from different habitats. Cultures of all strains were established successfully for molecular characterization. The small subunit ribosomal RNA genes of all strains were sequenced and compared to one another, to the neotype of S. diploidea, and to strains of Sappinia pedata, the only other Sappinia species known to date, from GenBank by multiple sequence alignment and cluster analysis. Altogether, the phylogenetic position of the genus Sappinia within the Thecamoebidae was corroborated; however, it was shown that the genus splits into several well-separated clusters making the establishment of new species within this genus inevitable. Furthermore, two of the S. diploidea-like strains were actually more closely related to S. pedata than to S. diploidea, although the diagnostically relevant standing form which seems to be characteristic for S. pedata was not observed in either of the two strains.