The Heterolobosea

The Heterolobosea and related amoeba
Page updated 11/7/02
Class: Heterolobosea Order: Schizopyrenida Genera: Adelphamoeba, Heteramoeba, Naegleria, Neovahlkampfia, Paravahlkampfia, Psalteriomonas, Sawyeria,
A group of small limax amoebae from fresh and sea water some of which produce cysts flagella or both. A large number of described species and genera have been placed in this group including the very common Naegleria some of which are pathogenic to man and other animals. There has been a tendency to place amoeba that are not Naegleria in the genus Vahlkampfia, however, amoeba previously placed in this genus have been found not to be mono-phylogenic (Brown & De Jonckheere, 1999). Morphogenic characteristics such as the possession of a cyst stage and/or a flagellate stage occur sporadically in many of the proposed genera. The heterolobosea also contain organisms such as Percolomonas cosmopolitus which are not thought to produce an amoeboid stage.
	Figure 1. Phylogenetic relationship of some members of the Vahlkampfia and related amoeba based on SSUrDNA gene analysis (Clustal W), using the barely related Entamoeba as an outgroup. Some names have been changed in accordance with recent suggestions (Brown & De Jonckheere, 1999). This figure illustrates the huge diversity present in the SSUrDNA gene itself and by inference at least, in these organisms genome in general.
Other members? The heterolobosea is almost certainly home to Acrasis however no SSUrDNA sequence for this genera is yet available. This kinship was suggested first by a close morphological and behavioural (locomotion pattern) examination (Page & Blanton, 1985; Page, 1978), and the class Heterolobosea was raised to unite Acrasis with the Schizopyrenida (Page & Blanton, 1985). Molecular data from Glyceraldehyde-3-phosphate dehydrogenase (Roger et al, 1996), tubulin (Roger et al, 1999; Keeling & Doolittle, 1996), CCT chaperonins (Archibald et al, 2002) and EF1a (Roger et al, 1999), all indicate an affinity between Acrasis and the Heterolobosea. This relationship is surprising given the similarity of Acrasis with Dictyostelium, a slime mould now recognised as being related to metazoans (). It has been noted that schizopyrenid amoeba have circular ribosomal genes (Clark & Cross, 1988), and that this feature is also shared with certain organisms that have been assumed to belong to the myxomycetes (Einvik et al, 1998), such as Didymium. Perhaps this genus also belongs to the heterolobosea? It has been suggested that Stachyamoeba is also a Heterolobosean (Page, 1987).
References:- Archibald, J. M., O'Kelly, C. J. & Doolittle, W. F. (2002) The chaperonin genes of Jakobid-like flagellates: Implications for eukaryotic evolution. Mol.Biol.Evol. 19, 422-431. Brown, S. & De Jonckheere, J. F. (1999) A reevaluation of the amoeba genus Vahlkampfia based on SSUrDNA sequences. Eur.J.Protistol. 35, 49-54. Clark, C. G. & Cross, G. A. M. (1988) Circular ribosomal RNA genes are a general feature of Schizopyrenid amoebae. J.Protozool. 35, 326-329. Einvik, C., Elde, M. & Johansen, S. (1998) Group I twintrons: Genetic elements in myxomycete and schizopyrenid amoeboflagellate ribosomal DNAs, J.Biotechnology. 64, 63-74. Keeling, P. J. & Doolittle, W. F. (1996) Alpha-tubulin from early-diverging eukaryotic lineages and the evolution of the tubulin family. Mol.Biol.Evol. 13, 1297-1305. Page, F. C. (1978) Acrasis rosea and the possible relationship between Acrasida and Schizopyrenida., Arch. Protistenk. 120, 169-181. Page, F. C. (1987) Transfer of Stachyamoeba lipophora to the Class Heterolobosea. Arch.Protistenkd. 133, 191-197. Page, F. C. & Blanton, R. L. (1985) The Heterolobosea (Sarcodina: Rhizopoda), a new class uniting the Schizopyrenida and the Acrasidae (Acrasida). Protistologica. 21, 121-132. Roger, A. J., Smith, M. W., Doolittle, R. F. & Ford Doolittle, W. (1996) Evidence for the Heterolobosea from phylogenetic analysis of genes encoding Glyceraldehyde-3-phosphate dehydrogenase. J.Euk.Microbiol. 43, 475-485. Roger, A. J., Sandblom, O., Doolittle, W. F. & Philippe, H. (1999) An evaluation of elongation factor 1a as a phylogenetic marker for eukaryotes. J.Mol. Evol. 16, 218-233.