Expression of the eicosapentaenoic acid synthesis gene cluster from Shewanella sp. In a transgenic marine cyanobacterium, Synechococcus sp.

The eicosapentaenoic acid (EPA) synthesis gene cluster isolated from a marine bacterium, Shewanella putrefaciens strain SCRC-2738, was cloned and expressed in the marine cyanobacterium Synechococcus sp. A broad-host-range cosmid vector, pJRD215 (10.2 kb, Sm(r) Km(r)), was used to clone a 38 kb insert, pEPA, containing the EPA synthesis gene cluster, creating plasmid pJRDEPA (approx. 48 kb). This plasmid was transferred to the cyanobacterial host at a frequency of 2.2. x 10^-7. Cyanobacterial transconjugants grown at 29°C produced 0.12 mg EPA (g dry weight)^-1, whereas those grown at 23°C produced 0.56 mg EPA (g dry weight)^-1. The yield was further improved to 0.64 mg (g dry weight)^-1 by incubation for 1 d at 17°C. This is believed to be the first successful cloning and expression of such a large heterologous gene cluster in a marine cyanobacterium.