Characterization of Selenaion koniopes n. gen., n. sp., an Amoeba that Represents a New Major Lineage within Heterolobosea, Isolated from the Wieliczka Salt Mine

Abstract

A new heterolobosean amoeba, Selenaion koniopes n. gen., n. sp., was isolated from 73‰ saline water in the Wieliczka salt mine, Poland. The amoeba had eruptive pseudopodia, a prominent uroid, and a nucleus without central nucleolus. Cysts had multiple crater-like pore plugs. No flagellates were observed. Transmission electron microscopy revealed several typical heterolobosean features: flattened mitochondrial cristae, mitochondria associated with endoplasmic reticulum, and an absence of obvious Golgi dictyosomes. Two types of larger and smaller granules were sometimes abundant in the cytoplasm--these may be involved in cyst formation. Mature cysts had a fibrous endocyst that could be thick, plus an ectocyst that was covered with small granules. Pore plugs had a flattened dome shape, were bipartite, and penetrated only the endocyst. Phylogenies based on the 18S rRNA gene and the presence of 18S rRNA helix 17_1 strongly confirmed assignment to Heterolobosea. The organism was not closely related to any described genus, and instead formed the deepest branch within the Heterolobosea clade after Pharyngomonas, with support for this deep-branching position being moderate (i.e. maximum likelihood bootstrap support--67%; posterior probability--0.98). Cells grew at 15-150‰ salinity. Thus, S. koniopes is a halotolerant, probably moderately halophilic heterolobosean, with a potentially pivotal evolutionary position within this large eukaryote group.

Neovahlkampfia nana n. sp. Reinforcing an Underrepresented Subclade of Tetramitia, Heterolobosea

“…Irregular aggregations of amorphous material (“A”) and dense black bodies (“B”) observed in the cytoplasm of the halophilic heterolobosean Selenaion koniopes (Park et al. ) resemble structures that we detected incidentally in Naegleria strains in our other studies but they differ substantially from those documented in our strain UD12. Pánek et al.…”

“…; Park et al. ). A substantial number of molecular studies have been conducted on five of these seven clades (e.g.…”

Dactylomonas gen. nov., a Novel Lineage of Heterolobosean Flagellates with Unique Ultrastructure, Closely Related to the Amoeba Selenaion koniopes Park, De Jonckheere & Simpson, 2012

“…While the nucleus of most heteroloboseans contains a single central or subcentral nucleolus, the nucleoli of members of Selenaionidae are clearly parietal (Park et al. ; this study). However, parietal nucleoli are also known from unrelated heterolobosean genera Stachyamoeba and Heteramoeba and some members of the family Psalteriomonadidae (Droop ; Page ; Pánek et al.…”

“…Interestingly, Selenaion koniopes , the closest relative of Dactylomonas , is aerobic (Park et al. ). Although the heteroloboseans are mostly aerobic, anaerobic species have been found in at least three separate lineages (see Introduction).…”

“…, ; Park et al. , ; Walochnik and Mulec ). Members of Heterolobosea are typically amoeboflagellates that alternate between amoeba and flagellate stages during the life cycle (Pánek et al.…”