About Galdieria

The unicellular red micro-alga Galdieria sulphuraria (Cyanidiales) is a eukaryote that can represent up to 90% of the biomass in extreme habitats such as hot sulfur springs with pH values of 0 to 4 and temperatures of up to 56°C. This red alga thrives autotropically as well as heterotropically on more that 50 different carbon sources, including a number of rare sugars and sugar alcohols.

Taxonomic position:

Species: G. sulphuraria; Genus: Galdieria; Family: Cyanidiaceae; Class: Rhodophyta

The taxonomic positions of Cyanidium, Cyanidioschyzon and Galdieria have been recently updated (Albertano et al., 2000). Previously, more than one organism has been referred to under the name Cyanidium caldarium. Based on detailed studies of morphology and the modes of cell division, three independent species have been established: Galdieria sulphuraria, Cyanidium caldarium, and Cyanidioschyzon merolae (De Luca et al., 1978; Merola et al., 1981). Moreover, the strains Cyanidium caldarium (Allen), Cyanidium caldarium M-8, and Cyanidium caldarium Forma B are considered to be identical with G. sulphuraria, while Cyanidium caldarium RK-1 and Cyanidium caldarium Forma A correspond to Cyanidium caldarium. This proposed taxonomy is also in concordance with recent molecular evidence (Cozzolino et al., 2000; Oliveira and Bhattacharya, 2000). See also Ciniglia et al. (2004) for a recent study on the phylogenetic framework of Cyanidales.

Albertano, P.; Ciniglia, C.; Pinto, G.; Pollio, A. (2000). The taxonomic position of Cyanidium, Cyanidioschyzon and Galdieria: an update. Hydrobiologia 433: 137-143

Ciniglia, C.; Yoon, H.S.; Pollio, A.; Pinto, G.; Bhattacharya, D. (2004). Hidden biodiversity of the extremophilic Cyanidiales red algae. Mol Ecol 13: 1827-1838

Cozzolino, S.; Caputo, P.; De Castro, O.; Moretti, A.; Pinto, G. (2000). Molecular variation in Galdieria sulphuraria (Galdieri) Merola and its bearing on taxonomy. Hydrobiologia 433: 145-151

De Luca, P.; Taddei, R.; Varano, L. (1978). Cyanidioschyzon merolae: a new alga of thermal acidic environments. Webbia 33: 37-44

Kuroiwa, T.; Nagashima, H.; Fukuda, I. (1989). Chloroplast division without DNA synthesis during the life cycle of the unicellular alga Cyanidium caldarium M-8 as revealed by quantitative fluorescence microscopy. Protoplasma 149: 120-129

Merola, A.; Castaldo, R.; De Luca, P.; Gambardella, R.; Musachio, A.; Taddei, R. (1981). Revision of Cyanidium caldarium. Three species of acidophylic algae. Giorn Bot Ital 115: 189-195

Oliveira, M. C.; Bhattacharya, D. (2000). Phylogeny of the Bangiophycidae (Rhodophyta) and the secondary endosymbiotic origin of algal plastids. Am J Bot 87: 482-492

Suzuki, A.; Kawano, S.; Kuroiwa, T. (1994). Single mitochondrion in Cyanidium caldarium and Galdieria sulphuraria (Rhodophyta, Cyanidiophyceae). Phycologia 33: 298-300

Ultrastructure:

Size: 3-9 μm; highly proteinaceous cell wall; single chloroplast (Kuroiwa et al., 1989) with chlorophyll a, phycocyanin and allophycocyanin; one single mitochondrion (Suzuki et al., 1994) and several peroxisomes; floridean starch outside the chloroplast.