DNA Sequence Analysis of Freshwater Eustigmatophyceae, a Potential Source of Essential Fatty Acids

Freshwater Eustigmatophyceae are a group of microalgae that are considered rare and of low diversity, with only a few genera and species in a single order. Some Eustigmatophyceae produce fatty acids that are important nutrients for aquaculture, as well as for human food consumption. In addition, some Eustigmatophyceae produce hydrocarbons that may be useful in biofuel production. In our studies of the diversity of coccoid algae from Itasca State Park, Minnesota, we discovered several isolates that we tentatively identified as Eustigmatophyceae. Preliminary molecular characterization indicated that these isolates were highly diverse and probably represented species new to science. In this study, we examined fifteen of the Eustigmatophyceae isolates from Itasca State Park using DNA sequence analysis of the plastid rbcL gene. Phylogenetic analyses of these sequences strongly supported Eustigmatophyceae as a monophyletic group and indicated two distinct lineages among our isolates within Eustigmatophyceae. Our results suggest that many of these isolates represent new genera and species. We can also infer the existence of at least two orders in the Eustigmatophyceae, based on the presence of two distinct lineages in the class. In addition to the taxonomic implications, this study will aid in the selection of isolates for further characterization of fatty acids and hydrocarbons, or as part of a regenerative life support system during extended space missions