Cultivation of Wild-type and Transgenic P. morum

The wild-type P. morum strain SAG 32.96 was obtained from the Culture Collection of Algae at Goettingen University (SAG), Germany. Cultures were maintained in Jaworski medium (JM) [47 ] at 29°C in an 8 h dark/16 h light (~10,000 lux) cycle [11 (link),20 (link)]. Cultures were grown in 10 ml glass tubes, 50 or 300 ml Erlenmeyer flasks, or 1,000 ml Fernbach flasks. The glass tubes had caps that allow for gas exchange, and Erlenmeyer and Fernbach flasks were aerated via Pasteur pipettes with approximately 50 cm³ sterile air/min [11 (link),20 (link)]. Transgenic strains that express the aphVIII gene were grown in JM in the presence of 1 μg paromomycin/ml (paromomycin sulfate, Sigma-Aldrich, St. Louis, MO).