Furthermore, some techniques to analyze the physiological status of the cells will be

summarized. Media, culture treatment, and illumination conditions In contrast to inducing selleck chemicals micronutrient deficiency in C. reinhardtii, which takes a lot of effort to exclude trace amounts of metal ions from the growth medium (Quinn and Merchant 1998), it is not difficult to deprive C. reinhardtii cells of the macronutrient sulphur (S). Standard TAP medium (Harris 1989, 2009) contains about 0.5 mM of sulphate. 400 μM of the latter derive from the salt solution, and about 100 μM originates from the trace element solution, which contains sulphate salts of Zn, Cu, and Fe. To prepare S-free medium, AZ 628 purchase the standard SBI-0206965 TAP recipe is used, but the Beijerinck’s salt solution is prepared with MgCl2 instead of using MgSO4. Accordingly, the trace element solution contains the chloride salts of Zn, Cu, and Fe. Double distilled water should be used for the preparation of the stock solutions and the media to avoid sulphate contamination. To induce S deprivation in C. reinhardtii, the cells are grown in standard TAP medium in the light and then transferred to S-free medium. For this purpose, the cells are centrifuged as described above, the supernatant is discarded, and the cell pellet is gently resuspended in the original volume of S-free medium. Another centrifugation

step follows, the supernatant is discarded once more, and the cells are resuspended in

S-free medium again. There are several philosophies on how many washing steps should be carried out. Some research groups carry out up to five washing steps (e.g., Kosourov et al. 2002), whereas others wash only once (Hemschemeier et al. 2008). It should be kept in mind that every centrifugation step affects the algal cells and may induce an anaerobic metabolism already, on the other hand, some sulphate might stick to the cells so that one washing Calpain step could be insufficient to remove any S from the cells. The procedure might be chosen according to the experimental aims. An alternative approach to deprive algal cells of S is to inoculate them in a medium with a limited amount of sulphate (Zhang et al. 2002). We experienced that inoculating a low amount of C. reinhardtii cells grown in standard TAP medium in new medium containing 50 μM sulphate (by adding a sterile MgSO4 stock solution to S-free TAP medium) allows them to grow until they reach a chlorophyll content of about 20 μg ml−1. Then, they will pass to the S-deprived stage and induce the set of adaptations figured out below. There is an easy method to check whether the Chlamydomonas culture already experiences S starvation. Several green algal species such as C. reinhardtii secrete a periplasmatic arylsulfatase as soon as they sense limitations of sulphate (Lien and Schreiner 1975).