Molecular phylogeny of Botryococcus braunii strains (race A) - An integrative approach

Botryococcus braunii is a green colonial microalga which produces large quantities of liquid hydrocarbons similar to fossil petroleum. Exploring Botryococcus genus diversity entailed morphological, biochemical and phylogenetic studies. The majority of scientific literature specifies B. braunii as the only species with strains classified in three chemical races (A, B and L) which superpose the phylogenetic clusters built on 18S rDNA sequences. The cohesion of data provided by the three main research directions relies on the integrative analysis of the Botryococcus strains. The present work addresses the diversity of B. braunii race A strains by taking into account the morphology, the hydrocarbon and fatty acid profiles, and the phylogeny of 10 strains, isolated from several Romanian aquatic environments. The newly sequenced B. braunii strains increased the resolution of the analyses and yielded at least two distinct phylogenetic clades within race A cluster. This outcome was sustained by the genetic information coded by the 18S rRNA genes and both sequence- and sequence-structure analysis of ITS2. The Compensatory Base Changes occurrence within the secondary structure of ITS2 and the presence of one intron in the 18S rDNA sequences gave extra credibility to our phylogenetic results.