Cell dry weight concentrations were measured directly as ash- free dry weight (AFDW) (Pinchuk et al., 2010 (link)) and compared in a standard curve to the indirect OD730 measurements obtained using a Genesys 20 visible spectrophotometer (Thermo Scientific, Rockford, IL). Protein was quantitated using BCA protein reagent (Thermo Scientific). Chl a and phycocyanin concentrations were estimated using a previously described method that corrects the effect of scatter on absorbance from whole-cell suspensions (see Supplemental Methodologies) (Myers, 1980 ; Burns et al., 2006 (link)). Dissolved O2 concentration in the reactor was measured with a Clark O2 electrode (InPro® 6800Series, Mettler Toledo International Inc., Columbus, OH). O2 production rates as a function of “white light” irradiance (tungsten incandescent) were measured inside an oxygraph chamber (Hansatech, Norfolk, UK).
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