Morphology and Phylogenetic Analyses of Three Novel Naegleria Isolated from Freshwaters on Jeju Island, Korea, During the Winter Period

Abstract

The genus Naegleria is one of the best known heterolobosean groups, and is the causative agent of primary amoebic meningoencephalitis. This group is rarely studied in temperate regions during winter. Here, three novel Naegleria were isolated from freshwaters on Jeju Island, Korea, during winter. Two isolates were amoeboflagellates, and one of the three amoebae did not undergo enflagellation. All amoebae had eruptive pseudopodia, and the layer of refractile granules around a large nucleus. They formed a cyst with~2 pores in the cyst stage. The amoeboflagellate form had two flagella and no division in the flagellate stage, and no cytostome. These features are very similar to typical Naegleria. Furthermore, our isolates were able to grow at > 30°C, suggesting that they had different thermophilicity from Naegleria in polar regions. All amoebae were largely encysted at 5 or 10°C, indicating that they were likely encysted during winter. Based on the 18S rRNA gene and the ITS1-5.8S rRNA gene-ITS2 sequences, the phylogenetic analyses consistently revealed that the isolates are members of the Naegleria group. However, the isolates differ from other species in both phylogenetic trees. Thus, Naegleria in cold habitats appeared to have a high degree of novelty, but their thermophilicity may be dependent on locality.

A New Halophilic Heterolobosean Flagellate, Aurem hypersalina gen. n. et sp. n., Closely Related to the Pleurostomum‐Tulamoeba Clade: Implications for Adaptive Radiation of Halophilic Eukaryotes

“…Heterolobosea are typically found in soil, freshwater, and marine environments, as well as in extreme habitats (Harding and Simpson ; Khwon and Park ; Pánek et al. , ; Park ; Tyml et al.…”

The Diversity Patterns of Rare to Abundant Microbial Eukaryotes Across a Broad Range of Salinities in a Solar Saltern

“…Moreover, the species inventory of other halophilic/halotolerant groups in Heterolobosea was further expanded. Several OTUs related to typical freshwater or marine heterolobosean species (e.g., Naegleria and Heteramoeba ) were recovered from high-salinity waters, and they may form cysts to remain viable [ 18 , 81 , 82 ]. Similar to our results, Post et al [ 74 ] reported that Neagleria spp.…”

Accumulation patterns of intracellular salts in a new halophilic amoeboflagellate, Euplaesiobystra salpumilio sp. nov., (Heterolobosea; Discoba) under hypersaline conditions

“…The experiment was performed on cultures of 'ES010' incubated at 50, 100, and 150 PSU for 7 days. In addition, the freshwater species Naegleria neojejuensis was used as a negative control (Khwon and Park, 2018). The cells were concentrated by centrifugation at 5,000 × g for 30 min.…”

“…The length of the cytostome in the flagellate phase of Pharyngomonas (>9 μm) longer than that in E. salpumilio, whereas Willaertia has cytostome (Patterson et al, 2000;Park and Simpson, 2011). Naegleria flagellates have two flagella, but lack a cytostome (Khwon and Park, 2018). Tulamoeba is isolated from hypersaline environments and has two flagella, but the flagellates show an elongated shape (Kirby et al, 2015) rather than the spherical shape of E. salpumilio.…”

“…nov. with (A) CoroNa Green (for Na + ) and (B) ION Potassium Green (for K + ) at increasing external salinities. The freshwater amoeba Naegleria neojejuensis was used as a negative control (see Khwon and Park, 2018). Note that fluorescence images were taken for 10 s at 5 s intervals, after which a light microscopy image was immediately obtained.…”