reinhardtii cells, PAM fluorometry, 77-K fluorescence emission, and chlorophyll fluorescence induction experiments (Wykoff et al. 1998), as well as spectrophotometric measurements of absorbance differences to determine the concentrations of functional PSII and PSI reaction centers

or cytochrome f in isolated thylakoid membranes (Melis et al. 2000) (see below). Other methods were utilized in order to analyze the H2 metabolism. The three indicators for 5-Fluoracil cell line the latter are usually in vitro hydrogenase activity assays as described above, in vivo assays (see below), and the analysis of the gas phase of the cells by GC. However, for all these experiments, the samples are usually taken from a culture vessel to be analyzed in different devices. This always perturbs the

equilibrium of the system, since a volume is extracted from the incubation vessel, and the sample itself will be exposed to air to a certain extent. Therefore, optimal experimental conditions combine the recordings of several relevant data in one sample, preferably in the culture vessel or the photobioreactor itself. Such systems, measuring pH, dissolved O2, redox potential, and chlorophyll fluorescence simultaneously in one photobioreactor have been described (e.g., H 89 manufacturer Kosourov et al. 2002; Antal et al. 2003), and they allow the direct relation of photosynthetic parameters such as PSII chlorophyll

fluorescence with other indicators such as dissolved O2 concentration and redox potential. Using such a photobioreactor setup, Antal et al. (2003) could demonstrate a clear relationship between a rapid drop of PSII efficiency and the onset of anaerobiosis, and could further find evidence that the hydrogenase enzyme provided a sink for electrons in the absence of the usual electron-consuming pathways such as CO2 fixation. A very convenient system to study the exchange of gases in C. reinhardtii Ribonucleotide reductase cell suspensions is a so-called Membrane Inlet Mass Spectrometer (MIMS). The setup is very useful to study the production or exchange of gases in liquid samples in general, e.g., in aqueous PSII solutions (Messinger et al. 1995; Shevela et al. 2008; Konermann et al. 2008), and it is described in detail in the article by Beckman et al. (On-line Mass spectrometry: Membrane Inlet sampling) in this issue. A MIMS has been established, for instance, in a research group at CEA Cadarache, France (Laurent Cournac, Gilles Peltier, Départment d’Ecophysiologie Vegétale et de Microbiologie, CEA Cadarache, France) (Dimon et al. 1988; Lindberg et al. 2004). Here, a measuring chamber of the Hansatech DW2/2 type (Hansatech, Norfolk, England, www.​hansatech-instruments.​com/​index.