Galdieria sulphuraria

Image of Galdiera sulphuraria courtesy of National Geographic.

Classification

Domain: Eukaryota; Class: Rhodophyta; Family: Cyanidiaceae; Genus: Galdieria

Phylogeny of ATPases in G. sulphuria Gerald Schönknecht et al. [Science 339, 1207 (2013).]

Species

Species: Galdiera sulphuraria

Description and Significance

Galdieria sulphuraria is a eukaryotic, spore-forming, coccus. G. sulphuraria appears yellow-green to dark blue-green grown heterotrophically in liquid culture, and often yellow or green in its natural environment[1]. It is an acidophile, as well a thermophile, and inhabits highly acidic springs at high temperatures[4].

G. sulphuraria is a mixotrophic organism capable of both photosynthesis and the catabolism of a wide variety of metabolites[3].

Genome Structure

Phylogenetic and genomic analyses supplied by, Gerald Schönknecht et al. revealed 75 indications of horizontal gene transfer from archaea and bacteria along with highly condensed protein coding regions within the G. sulphuraria genome [6]. It is speculated that minimally 5% of the functional genes were acquired in this way [1].

Success of G. sulphuraria in a diverse array of extreme habitats appears to be facilitated by the acquisition and subsequent duplication of variety of genes not limited to heat tolerant archael ATPases, bacterial halophilic sodium-proton antiporters and thermoacidophilic arsenical membrane protein pumps along with the metal reducing mercuric reductase native to proteobacteria [6].

In addition to extremophilic adaptations, fungal metabolite transporters contribute to G. sulphuria's ability to utilize a medley of unusual carbon sources and distinguish it genetically even from "closely" related species [6].

Cell Structure, Metabolism and Life Cycle

G. sulphuraria is a mixotrophic eukaryote presenting a multilobed chloroplast and net-like mitochondrion [2].

G. sulphuraria is capable of metabolic flexability, with the ability to grow photoautotrophically, photoheterotrophically, or chemoheterotrophically on greater than 50 carbon sources [3]. Experiments into growing G. sulphuraria in laboratory conditions conditions determined that G. sulphuraria growth is inhibited at concentrations of glucose and fructose above 166 grams/liter and ammonium sulfate above 22 grams/liter[8].

G. sulphuraria reproduces via the formation of 4-32 spores[2].

Ecology

Image of Galdieria sulphuraria in Reykjavik http://www.nationalgeographic.com National Geographic.

G. sulphuraria is found in extreme habitats such as the hot sulfur springs of Italy, Russia, Yellowstone park, and Iceland in pH values between 0 and 4 and in temperatures up to 56 degrees Celsius [4]. It can also tolerate high metal concentrations [5].

G. sulphuraria can make up up to 90% of the total microbial mass in some environments [1], however it often exists alongside Cyanidioschyzon merolae and Cyanidium caldarium [7].