Date of Graduation

12-2011

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Cell & Molecular Biology (PhD)

Degree Level

Graduate

Department

Biological Sciences

Advisor

Frederick W. Spiegel

Committee Member

Stephen L. Stephenson

Second Committee Member

Ines Pinto

Third Committee Member

Allen L. Szalanski

Keywords

Biological sciences, Amoebae, Amoebozoa, Eumycetozoa, Mycetozoa

Abstract

Because of their simple fruiting bodies consisting of one to a few spores atop a finely tapering stalk, protosteloid amoebae, previously called protostelids, were thought of as primitive members of the Eumycetozoa sensu Olive 1975. The studies presented here have precipitated a change in the way protosteloid amoebae are perceived in two ways: (1) by expanding their known habitat range and (2) by forcing us to think of them as amoebae that occasionally form fruiting bodies rather than as primitive fungus-like organisms. Prior to this work protosteloid amoebae were thought of as terrestrial organisms. Collection of substrates from aquatic habitats has shown that protosteloid and myxogastrian amoebae are easy to find in aquatic environments. Also, prior to this work the Eumycetozoa sensu Olive 1975, was a supposedly monophyletic taxon that included protosteloid amoebae as basal to Myxogastria and Dictyostelia. Three studies presented here erode this idea. These studies include a brief review of the diversity in nucleolar ultrastructure present among eumycetozoans in which new transmission electron micrographs of the protosteloid amoeba Echinosteliopsis oligospora are presented. Further, phylogenetic analyses of protosteloid amoebae based on the gene sequences of the small subunit of the ribosomal RNA (SSU rDNA) show that protosteloid amoebae are polyphyletic within the eukaryote supergroup, Amoebozoa, and that some are deeply embedded within well characterized lineages of nonfruiting amoebae, i.e., vannellids and acanthamoebids. As a result, we now call these simple, fruiting amoebae 'protosteloid amoebae' as opposed to 'protostelids' since the latter implies (incorrectly) that these organisms comprise a natural phylogenetic group. These molecular phylogenetic analyses suggest that isolate LHI05 represents a new protosteloid species that branches among the Acanthamoebidae, an amoebozoan taxon in which fruiting amoebae have never previously been described. Thus a new genus and species, Luapeleamoeba hula g. ad interim sp. ad interim, are proposed to accommodate protosteloid isolate LHI05. Suggestions for additional taxonomic revision are presented as are suggestions for future research particularly with respect to molecular phylogenetic, phylogenomic, and evolutionary/developmental biological approaches. Finally, this work has prompted critical thinking about the origins and evolution of simple fruiting bodies and complex life cycles among amoebozoans, and these basic biological questions are discussed.

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