Effects of overexpression of Escherichia coli katE and bet genes on the tolerance for salt stress in a freshwater cyanobacterium Synechococcus sp. PCC 7942

Abstract To explore the potential role of catalase and glycine betaine in the protection of cyanobacteria from damage due to salt stress, we transformed a freshwater cyanobacterium Synechococcus sp. PCC 7942 with shuttle vectors that contained the Escherichia coli kat E, bet , and kat E plus bet ( kat E/ bet ) genes. The catalase activity in the cells overexpressing kat E and kat E/ bet genes was about 1.4–1.8-fold higher than that in the control cells. The control and transformant cells had a similar growth rate in the medium with a low salinity. However, under a high-salinity condition, the cells transformed with kat E grew faster than the control cells, and the cells expressing kat E/ bet genes grew faster than those expressing either the kat E or bet gene alone. These results indicate that high-salinity caused oxidative stress and the coexpression of kat E and bet genes in Synechococcus cells were superior to the expression of either kat E or bet alone for the protection of the cells from the damage due to high-salinity.