Ubiquity of Euglena mutabilis Population in Three Ecologically Distinct Acidic Habitats in Southwestern Japan

Katsunori Yanagawa,Kei Yamashita,Jun-Ichiro Ishibashi,Kai Yoshitake,Akira Haraguchi,Masanari Harano,Katsuhiro Asamatsu

doi:10.3390/w13111570

Abstract

Three strains of Euglena mutabilis were isolated from sediments in acidic inland water systems (pH = 3.4–4.7), in Southwestern Japan—acid mine drainage in Sensui (Fukuoka), cold sulfidic spring in Bougatsuru (Oita), and a temporal pool in the Ebinokogen volcanic area (Miyazaki). All strains grew well in acidic media at pH 3.07. Phylogenetic analysis among these three strains showed high similarities to plastid SSU and nuclear SSU rRNA gene sequences (99.86% and 99.76%, respectively). They were closely related to the cultured isolates from other highly acidic habitats (pH = 2.0–5.9). Concentration of sulfate, aluminum, calcium, and iron had 7–70 fold of differences among the three studied habitats. Our results imply that the rRNA genes of E. mutabilis have compensated for their low genetic diversity by adapting to a wide pH range, as well as various water chemistry of habitats.

Highlights

The flagellate Euglena mutabilis Schmitz is distributed in highly acidic inland water systems, such as coal or metal mine drainages [1,2], volcanic streams [3], and peat mire [4,5]
The first objective of the present study was to identify the benthic Euglena strains by phylogenetic analysis of plastid SSU and nuclear SSU rRNA genes
Phylogenetic analysis among three strains of E. mutabilis isolated from sediments in acidic inland water systems in Southwestern Japan showed high similarities to plastid SSU and nuclear SSU rRNA gene sequences

Summary

Introduction

The flagellate Euglena mutabilis Schmitz is distributed in highly acidic inland water systems, such as coal or metal mine drainages [1,2], volcanic streams [3], and peat mire [4,5]. The lower pH limit of E. mutabilis habitats was reported to be 1.5 in coal mining sites in England [7], 1.5–2.2 in the Rio Tinto drains in Southern Spain [8], and 3.1 in a coal mining site in Indiana [2]. Bray et al [9] reported that E. mutabilis could be found in circumneutral environments (pH = 5.5–6.5) in the Southern Island of New Zealand, its dominance within the algal community was low. The main habitats of E. mutabilis are acidic inland water systems with pH ranging from 1.5–4.7, and in algal communities under circumneutral environments

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