Burning coal spoil heaps as a new habitat for the extremophilic red alga Galdieria sulphuraria

Abstract

Galdieria sulphuraria (Cyanidiales) is a worldwide acclaimed thermoacidophilic red microalga with a limited distribution due to special conditions required for growth and metabolism. Until now, the alga was almost exclusively restricted to acid geothermal environments around the world. However, we have found this species on the surface of a burning coal spoil heap in central Europe. It is the first record of G. sulphuraria in this type of habitat. A rbcL phylogeny confirmed that the population of this extremophile belongs to the continental European lineage and we consider Italian geothermal sites as a potential source of Czech G. sulphuraria. The dispersal of unicellular red microalgae is far from fully understood and the discovery of Galdieria in another region of Europe on a relatively newly established anthropogenic site allows us to understand better the distribution patterns and dispersal abilities of this ecologically important algal group. In addition, we have also analyzed the phylogenetic position of Galdieria strain CCALA 965 isolated from a highly acidic site without geothermal activity in the Czech Republic and confirmed it to belong to the species G. phlegrea, until now known only from Italy.

Plastid‐encoded rbcL phylogeny suggests widespread distribution of Galdieria phlegrea (Cyanidiophyceae, Rhodophyta)

“…3). The new isolate from Tinto River fell within the G. phlegrea clade and it was identical (924 bps) to the strain CCALA 965 isolated from a mud pool discharging CO 2 in the Soos Nature Reserve in Czechia (Barcytė et al 2018). The same clade also accommodated sequences from Italy and Turkey (Fig.…”

“…Galdieria phlegrea Pinto, Ciniglia, Cascone et Pollio (Cyanidiophyceae, Rhodophyta) is a small unicellular autosporic coccoid alga originally found in extremely acidic habitats (pH 0.5-1.5) with moderately elevated temperatures (Ciniglia et al 2004, Pinto et al 2007). The alga was previously exclusively known from dry endolithic habitats in volcanically active areas in Italy, but was recently confirmed to also have grown in Czechia (Barcytė et al 2018), implying a possibly wider distribution than what has previously been assumed. Its closest relative, G. sulphuraria (Galdieri) Melora, has a cosmopolitan distribution (Ciniglia et al 2014) and is restricted to low pH (0.5-4.0) and high temperature (up to 56°C) environments.…”

“…The strain DB01 was further used for algal identification. To check the thermotolerant nature of the organism, we also cultivated the same strain at 35°C as described in Barcytė at al. (2018).…”

“…For phylogenetic analyses we used the same dataset as published by Barcytė et al (2018), including the new sequence and 24 additional sequences revealed by the BLAST algorithm (Altschul et al 1997) as close matches to the isolate DB01. In addition, we used the outgroup taxa Cyanidioschyzon merolae (AY119765) and Cyanidium caldarium (AY541298).…”

“…In addition, G. phlegrea underwent lineage-specific HGTs (Qiu et al 2013). Galdieria sulphuraria and G. phlegrea seem to be morphologically indistinguishable from each other (Pinto et al 2007, Barcytė et al 2018) and molecular phylogenetic analyses are crucial for correct species determination. Due to the specific ecophysiological requirements not commonly encountered in prokaryotes or eukaryotes, G. phlegrea is an excellent potential model species for studying microbial biogeography.…”