Expansion of the molecular and morphological diversity of Acanthamoebidae (Centramoebida, Amoebozoa) and identification of a novel life cycle type within the group.

Alexander K Tice,Steffen Clauß,Seungho Kang,Eckhard Voelcker,Frederick W Spiegel,Katherine A Wilkinson,Anna Maria Fiore-Donno,Lora L Shadwick,Michael Bonkowski,Kenneth Dumack,Daniel J G Lahr,Stefan Geisen,Junling Zhang,Gabriel A Schuler,Matthew W Brown

doi:10.1186/s13062-016-0171-0

Abstract

BackgroundAcanthamoebidae is a “family” level amoebozoan group composed of the genera Acanthamoeba, Protacanthamoeba, and very recently Luapeleamoeba. This clade of amoebozoans has received considerable attention from the broader scientific community as Acanthamoeba spp. represent both model organisms and human pathogens. While the classical composition of the group (Acanthamoeba + Protacanthamoeba) has been well accepted due to the morphological and ultrastructural similarities of its members, the Acanthamoebidae has never been highly statistically supported in single gene phylogenetic reconstructions of Amoebozoa either by maximum likelihood (ML) or Bayesian analyses.ResultsHere we show using a phylogenomic approach that the Acanthamoebidae is a fully supported monophyletic group within Amoebozoa with both ML and Bayesian analyses. We also expand the known range of morphological and life cycle diversity found in the Acanthamoebidae by demonstrating that the amoebozoans “Protostelium” arachisporum, Dracoamoeba jormungandri n. g. n. sp., and Vacuolamoeba acanthoformis n.g. n.sp., belong within the group. We also found that “Protostelium” pyriformis is clearly a species of Acanthamoeba making it the first reported sporocarpic member of the genus, that is, an amoeba that individually forms a walled, dormant propagule elevated by a non-cellular stalk. Our phylogenetic analyses recover a fully supported Acanthamoebidae composed of five genera. Two of these genera (Acanthamoeba and Luapeleameoba) have members that are sporocarpic.ConclusionsOur results provide high statistical support for an Acanthamoebidae that is composed of five distinct genera. This study increases the known morphological diversity of this group and shows that species of Acanthamoeba can include spore-bearing stages. This further illustrates the widespread nature of spore-bearing stages across the tree of Amoebozoa.ReviewersThis article was reviewed by Drs. Eugene Koonin, Purificacion Lopez-Garcia and Sandra Baldauf. Sandra Baldauf was nominated by Purificacion Lopez-Garcia, an Editorial Board member.Electronic supplementary materialThe online version of this article (doi:10.1186/s13062-016-0171-0) contains supplementary material, which is available to authorized users.

Highlights

Acanthamoebidae is a “family” level amoebozoan group composed of the genera Acanthamoeba, Protacanthamoeba, and very recently Luapeleamoeba
The Acanthamoebidae has been the focus of more scientific studies than many other amoebozoan groups owing to the medical and ecological importance as well as the role of A. castellanii as a model organism [3,4,5,6,7,8]
Morphological details confirming the identity of our isolates obtained from nature of these two species (originally described as Protostelium pyriformis (Fig. 1: a-f) and Protostelium arachisporum (Fig. 1: j-l) respectively) can be found in supplementary results

Summary

Introduction

Acanthamoebidae is a “family” level amoebozoan group composed of the genera Acanthamoeba, Protacanthamoeba, and very recently Luapeleamoeba. This clade of amoebozoans has received considerable attention from the broader scientific community as Acanthamoeba spp. represent both model organisms and human pathogens. Acanthamoebidae comprised two genera, Acanthamoeba and Protacanthamoeba [9]. Species of both these genera typically have flattened trophic cells that display pointed subpseudopodia (termed acanthopodia, see [10]) and a prominent lamellate microtubular organizing center (MTOC) [1, 9, 11]. Very recently a new amoeba genus represented only by the type species, Luapeleamoeba hula, was incorporated into the Acanthamoebidae primarily based on the sequence of its small subunit ribosomal RNA gene (SSU) [13, 14]

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