For this purpose, cells are grown in the light, either photoheterotrophically in Tris acetate phosphate (TAP) or photoautotrophically in high salt minimal (HSM) medium (Harris 1989, 2009). For all the physiological analyses of Chlamydomonas and other algae, it is important to keep the cells of ASP2215 precultures in the active growth phase. This means that as soon as the cultures have reached a cell density

of about 1 × 107 cells ml−1, an aliquot of this culture is used to inoculate fresh medium at a cell density of about 1–2 × 104 cells ml−1. For anaerobic adaptation of C. reinhardtii, a chlorophyll content of the pre-culture of 20–25 μg ml−1 has turned out to be optimal. The chlorophyll content of C. reinhardtii is determined by mixing 200 μl of cell suspension with 800 μl acetone, letting the chlorophylls extract for several hours in the refrigerator, spinning the cells down, and measuring the absorbance of the green supernatant against 80% acetone at λ = 652 nm (Arnon 1949). At a chlorophyll content of 20 μg ml−1, which is equivalent to about 6.5 × 106 cells ml−1 selleck kinase inhibitor in case of the C. reinhardtii wild type CC-124 (137c), the cells would have already reached the end of the exponential growth phase, but still divide. The pre-culture is then harvested by mild centrifugation (2 min at 3,500–5,000 g, room temperature) in Sarstedt (Sarstedt, Nümbrecht, Germany) or Falcon tubes and gently resuspended

in about 0.2 volumes of fresh medium PTK6 to reach a chlorophyll concentration of 100 μg ml−1. For reproducible and comparable results, both the respective pre-cultures and the concentrated cultures to be compared should have equivalent

chlorophyll contents. It is important for all the analyses of C. reinhardtii that the cells do not stand anywhere for more than 1 min, since they settle rapidly and establish microaerobic or even anaerobic conditions in the dense cell sediment. Accordingly, pellets of the algae should be QNZ resuspended rapidly. If the purpose of the experiments requires a real “0 h” sample, the concentrated cells may be incubated in a thin layer in Erlenmeyer flasks in the light to re-establish photosynthetic, thus O2-saturated conditions. For anaerobic adaptation, though the highly concentrated algal culture will not carry out appreciable photosynthesis due to self-shading, the tube should be further wrapped with aluminium foil to prevent the outer layers of the cell culture to be exposed to light. The algal suspension is then flushed by Ar or N2 at 18–25°C. For this purpose, a tube (about 5 mm in diameter) connected to the gas cylinder via a pressure regulator is introduced into the flask through a suitable hole in the lid, which should have a somewhat larger diameter than the tube to allow the gas to exhaust again. The tube is then dipped into the culture so that the gas flushes the cell suspension. It is important that the gas is of high purity, i.e., with no significant contaminations of O2.