Strains and Growth Conditions
UWO241 was grown axenically in Bold’s Basal Medium (BBM) supplemented with 10 mM NaCl, whereas C. reinhardtii cc-1690 was grown in BBM with 0.43 mM NaCl. All cultures were aerated continuously with ambient air filtered by a 0.2 µm filter in 250 ml glass growth tubes suspended in thermo-regulated aquaria. A continuous growth irradiance of 100 µmol photons m-2 s-1 was generated by fluorescent tubes (Sylvania CW-40) and measured with a quantum sensor attached to a radiometer (Model LI-189; Li-Cor). UWO241 cultures were grown at 4, 10, 15, 17 and 20°C and exposed to heat stress by transfer to 24°C. C. reinhardtii cultures were grown at 5, 10, 15, 28, 37 and 40°C and exposed to heat stress by transfer to 42°C. Mid-log cultures were used in all experiments.