Coelastrella

Abstract: A terrestrial green microalga was isolated at As, in Akershus County, Norway. The strain corresponded to a coccoid chlorophyte. Morphological characteristics by light and electron microscopy, in conjunction with DNA amplification and sequencing of the 18 s rDNA gene and ITS sequences, were used to identify the microalgae. The characteristics agree with those of the genus Coelastrella defined by Chodat, and formed a sister group with the recently described C. thermophila var. globulina. Coelastrella is a relatively small numbered genus that has not been observed in continental Norway before; there are no previous cultures available in collections of Norwegian strains. Gas chromatography analyses of the FAME-derivatives showed a high percentage of polyunsaturated fatty acids (44–45%) especially linolenic acid (C18:3n3; 30–34%). After the stationary phase, the cultures were able to accumulate several carotenoids as neoxanthin, pheophytin a, astaxanthin, canthaxanthin, lutein, and violaxanthin. Due to the scarcity of visual characters suitable for diagnostic purposes and the lack of DNA sequence information, there is a high possibility that species of this genus have been neglected in local environmental studies, even though it showed interesting properties for algal biotechnology.

Abstract: The genus Coelastrella was established by Chodat (Bull. Soc. Bot. Geneve, 13 [1922] 66), and was characterized as being unicellular or in few-celled aggregations with many longitudinal ribs on the cell wall. Many species of this genus showed strong ability to accumulate carotenoids and oils, so they have recently attracted much attention from researchers due to its potential applicability in the energy and food industries. In this study, a total of 23 strains of Coelastrella were sampled from China, and three new species and two new varieties were described: C. thermophila sp. nov., C. yingshanensis sp. nov., C. tenuitheca sp. nov., C. thermophila var. globulina var. nov., C. rubescens var. oocystiformis var. nov. Besides 18S rDNA and ITS2 sequences, we have newly sequenced the tufA gene marker for this taxon. Phylogenetic analysis combined with morphological studies revealed four morphotypes within the Coelastrella sensu lato clade, which contained the morphotype of original Coelastrella, original Scotiellopsis, Asterarcys, and morphotype of C. vacuolata and C. tenuitheca sp. nov. The relationships between morphological differences and phylogenic diversity based on different markers were discussed. Our results support that 18S rDNA was too conserved to be used a species-specific or even a genus-specific marker in this clade. The topology of tufA gene-based phylogenetic tree had a better match with the morphological findings.

Abstract: We taxonomically examined an algal strain (Ki‐4) isolated from a dry asphalt surface in mid‐summer of 2003. The vegetative cells were solitary, covered by a cell wall ornamented with meridional ribs, and contained hollow spherical chloroplasts and a pyrenoid. The cells exhibited a high tolerance to unfavorable photo‐oxidative stress conditions, and in culture developed a reddish coloration due to the accumulation of a water‐soluble astaxanthin‐binding protein, which was identified as a novel protein in organisms. 18S rDNA and ITS2 sequence analyses revealed that Ki‐4 belongs to Coelastrella sensu lato (Scenedesmaceae), but was taxonomically distinct from other members of the genus. On the basis of its phylogenetic position and morphological features, including the structures of cell wall ribs, we identify Ki‐4 as a new algal species in the genus Coelastrella, for which we propose the name Coelastrella astaxanthina sp. nov.

Abstract: Many species belonging to the coccoid green algae genus Coelastrella are considered potential candidates for the large-scale production of natural pigments and biofuels. However, little is known ab...