Genome size and phylogenetic analysis of the A and L races of Botryococcus braunii

Botryococcus braunii (Chlorophyta, Botryococcaceae) is a colony-forming green microalga that produces large amounts of liquid hydrocarbons, which can be converted into transportation fuels. There are three different races of B. braunii, A, B, and L, that are distinguished based on the type of hydrocarbon each produces. Each race also has many strains that are distinguished by the location from which they were collected. While B. braunii has been well studied for the chemistry of the hydrocarbon production, very little is known about the molecular biology of B. braunii. To begin to address this problem, we determined the genome size of the A race, Yamanaka strain, and the L race, Songkla Nakarin strain, of B. braunii. Flow cytometry analysis indicates that the A race of B. braunii has a genome size of 166.0 +/- 0.4 Mb, while the L race has a substantially larger genome size at 211.3 +/- 1.7 Mb. We also used phylogenetic analysis with the nuclear small subunit (18S) rRNA gene to classify strains of the A and B races that have not yet been compared evolutionarily to previously published B. braunii phylogenetics. The analysis suggests that the evolutionary relationship between B. braunii races is correlated with the type of liquid hydrocarbon they produce.