Morphological, biochemical, and phylogenetic assessments of eight Botryococcus terribilis strains collected from freshwaters of Transylvania.

Botryococcus braunii is a green unicellular microalga with a unique potential to produce large quantities of hydrocarbons similar to fossil fuel. Up to now, B. braunii is the most studied species of the Botryococcus genus. The taxonomic affiliation of eight different strains of the genus Botryococcus collected from freshwaters of Transylvania was investigated based on their morphological characteristics and molecular profile using small subunit (SSU) ribosomal RNA (rRNA) genes and internal transcribed spacer 2 (ITS2) sequence-structure analysis. The phylogenetic inference using ITS2 sequence-structure molecular marker, an approach addressed for the first time in the issue of Botryococcus genus phylogeny, generated similar results with the 18S rRNA gene based analysis. In both phylogenetic trees we constructed, the sequences of our strains formed an independent cluster within the B-race clade. Based on the phylogenetic data and the presence of long mucilaginous processes which emerged from the periphery of the colonies, we established the affiliation of our strains to Botryococcus terribilis species. Detailed analyses regarding the growth performances, ultrastructural characteristics, and hydrocarbon and fatty acid profiles were also included in our study. The micrographs obtained in scanning electron, transmission electron, and light microscopies showed a high degree of similarity to other strains affiliated to the B chemical race. Also, gas chromatography-mass spectrometry assay showed for the first time the ability of B. terribilis strains to synthesize C-C botryococcenes, which are known to be specific to the B-type Botryococcus strains. [ABSTRACT FROM AUTHOR]