An evolutionary perspective on selecting high-lipid-content diatoms (Bacillariophyta)

Diatoms (Bacillariophyta) characteristically accumulate valuable storage lipids throughout their entire life cycle and therefore are an appealing choice to be used as a feedstock for commercial products, like biodiesel. However, the incredible diversity of diatoms poses a substantial challenge when attempting to select the best species for commercial development. The present study compiled previously published data regarding diatom lipid content under nutrient-replete and nutrient(s)-deplete conditions as well as generating novel lipid and growth data from ten species of diatoms within lineages that have been historically under-examined. In this study, lipids were extracted via chloroform-methanol and quantified as percent dry weight and then analyzed for a phylogenetic signal by comparing the variability between lineages to the variability within lineages in an attempt to identify the lineages with the greatest lipid content. A nested ANOVA revealed that there was greater variability between lineages than within lineages when cultures were grown in a silica-deplete medium; the Biddulphiophycidae lineage accumulated a significantly lower amount of lipids than other lineages. The taxa examined in the present study were then paired with the data gathered from the literature and examined for a phylogenetic signal using previously described methods. In this analysis, a statistically significant phylogenetic signal was detected for nutrient(s)-deplete growth experiments (P = 0.013). These results suggest that under nutrient(s)-deplete conditions, lipid content is, in part, a heritable, evolutionary trait, and therefore, an evolutionary-based approach may be used to facilitate species selection by identifying the differences in lipid content between lineages.