The main photosynthetic pigment in Synechococcus is chlorophyll a, while its major accessory pigments are phycobilliproteins.[5] The four commonly recognized phycobilins are phycocyanin, allophycocyanin, allophycocyanin B and phycoerythrin.[11] In addition Synechococcus also contains zeaxanthin but no diagnostic pigment for this organism is known. Zeaxanthin is also found in Prochlorococcus, red algae and as a minor pigment in some chlorophytes and eustigmatophytes. Similarly phycoerythrin is also found in rhodophytes and some cryptomonads.