The Bioenergetics of Stress Responses in Cyanobacteria

Abstract

Our laboratory is trying to chart some new areas that offer attractive vistas for research in the response to stress in photosynthetic microorganisms. We use oxygenic photosynthetic cyanobacteria as a model system to examine stress responses. A useful approach has been to take a freshwater cyanobacterium suddenly exposed to seawater concentrations of sodium, and ask the question, ‘What are the steps involved in the adaptation of the organism to grow in high salt?’ In a similar way, we have investigated other kinds of stress, like temperature stress, toxic metal stress (change of the selenium to sulphur ratio), pH stress and photo-oxidative stress (Belkin et al., 1987). The question that we seek answers to are: do universal mechanisms of response to stress exist, and what are the specific responses that the organisms show when they are exposed to one or another kind of stress? This is obviously a complex problem that involves changes in gene expression, bioenergetic changes and, in the case of salt tolerance, of course, osmoregulatory changes (Blumwald et al., 1983a; Blumwald et al., 1983b).