Allovahlkampfia minuta nov. sp., (Acrasidae, Heterolobosea, Excavata) a New Soil Amoeba at the Boundary of the Acrasid Cellular Slime Moulds

We report the isolation of a new species of Allovahlkampfia, a small cyst-forming heterolobosean soil amoeba. Phylogenetic analysis of the 18S rDNA and the internal transcribed spacers indicates that Allovahlkampfia is more closely related to the acrasids than to other heterolobosean groups and indicates that the new strain (GF1) groups with Allovahlkampfia tibetiensis and A. nederlandiensis despite being significantly smaller than these and any other described Allovahlkampfia species. GF1 forms aggregated cyst masses similar to the early stages of Acrasis sorocarp development, in agreement with the view that it shares ancestry with the acrasids. Time-lapse video microscopy reveals that trophozoites are attracted to individuals that have already begun to encyst or that have formed cysts. Although some members of the genus are known to be pathogenic the strain GF1 does not grow above 28oC nor at elevated osmotic conditions, indicating that it is unlikely to be a pathogen.