Synechocystis sp. PCC6803 is known to occur in several distinct substrains, all going back to the same isolate deposited in the Pasteur Culture Collection.6 Indeed, several studies reported the differences between the genome sequence of Synechocystis sp. PCC 6803 published in 1996 (called here the ‘GT-Kazusa’ substrain) and the actual sequence found in different laboratories.7–10 A strain history has been proposed by Ikeuchi and Tabata8 with an early branching into the motile PCC strain and the non-motile ATCC 27184 strain. The latter lost motility due to a 1-bp insertion in the spkA gene coding for a eukaryotic-type Ser/Thr protein kinase11 and represents the origin of the glucose-tolerant (GT) strains5 to which also the ‘GT-Kazusa’ substrain belongs.