This protocol should be used for chlorophyll extraction in cyanobacteria. The equation for calculating the exact chlorophyll content can be found at the end of this document.You might want to measure the optical density (OD) of you cyanobacteria culture at 750 nm. Use BG11 medium or water as the reference solution. You need the OD of your culture to normalize the cholorphyll concentration to the number of cyanobacteria.Calculate chlorophyll content (adapted from Lichtenthaler 1978)Chl [µg/ml] = OD665nm x 13.9 [µg/ml] x dilution factor of cultureYou can take less than 1 ml, but note the dilution factor for the calculation later on, e.g. :1 ml sample = dilution factor of 1500 µl sample = dilution factor of 2100 µl sample = dilution factor of 10