Exposure of the Cyanobacterium Synechocystis PCC6803 to Salt Stress Induces Concerted Changes in Respiration and Photosynthesis

In order to survive and to grow in the presence of a high salinity(550 mM NaCl) Synechocystis PCC6803 increases its energeticcapacity. The salt-induced increase of electron transport ratesinvolves both cytochrome c oxidase and photosystem I. In contrast,electron transport rates measured through complexes I plus IIIof the respiratory chain, or through the photosystem II pluscytochrome b₆f complexes of the photosynthetic chain, do notshow appreciable changes. The time at which changes in electrontransport rates occur in the photosystem I and cytochrome coxidase complexes after the onset of salt stress indicates similaritiesin the adaptation of dark respiration and (cyclic) photosyntheticelectron flow. Given an increase of whole cell respiration andof PSI cyclic electron flow larger than the neosynthesis ofcytochrome aa3 and PSI reaction centers would predict, it appearsthat both adaptations require more than just synthesis of thesetwo complexes. (Received April 12, 1993; Accepted August 10, 1993)