SELECTIVE CONDITIONS AND ISOLATION OF MUTANTS IN SALT-TOLERANT,LIPID-PRODUCING MICROALGAE1

Suitable conditions for the isolation and selection of generic markers were determined by testing the growth of nine axenic strains of lipid-producing algae (representatives of Bacillariophyceae, Eustigmatophyceae, and Chlorophyceae) under a variety of conditions. Mixotrophic, heterotrophic, or anaerobic growth on twenty different carbon compounds was determined. In addition, ten different carbon compounds was determined. In addition, ten different nitrogen-containing compounds were supplied as the sole nitrogen source to ascertain which of these could be utilized. Resistances to various antibiotics and herbicides were also assessed. The algae utilized a variety of compounds as their sole nitrogen source, and some species also grew heterotrophically or mixotrophically on a variety of carbon compounds. This suggests that the algae are not only able to transport these compounds into the cell but that the biochemical pathways necessary for their utilization are present and could be targeted for mutagenesis. Anaerobic growth was not possible on any of the photosystem II inhibitors diuron and atrazine and the 70S ribosome inhibitors erythromycin and streptomycin. However, the diatoms were insensitive to spectinomycin and sulfometuron methyl. Information about drug sensitivities permitted the selection of drug resistant mutants. Mutagenized cultures produced colonies when plated on media containing drug concentrations that were growth-inhibiting for wild-type cultures. Mutations were recovered in Monoraphidium, Nannochloropsis and Navicula species.