CARBOHYDRATE ACCUMULATION IN OSMOTICALLY STRESSED CYANOBACTERIA (BLUE‐GREEN ALGAE): INTERACTIONS OF TEMPERATURE AND SALINITY

Abstract

S ummary The effects of temperature and salinity on the carbohydrate accumulation profiles of a range of unicellular cyanobacteria (blue‐green algae) have been studied. Four isolates of Synechocystis sp. which usually accumulated glucosyl‐glycerol produced a second carbohydrate, sucrose, when grown in a seawater‐based medium at high temperature (35°C). In contrast, three sucrose‐accumulating isolates of Synechococcus , grown over a range of temperatures and salinities, did not produce a second detectable low molecular weight carbohydrate in any experimental treatment. The interaction of temperature and salinity was further examined in Synechocystis PCC 6714. Sucrose production was found to be favoured by high temperature and low salinity. The rate and extent of sucrose accumulation differed in cells grown at 20 and 37 °C reaching an upper asymptote 12 h after upshock at 37 °C and 24 h after upshock at 20 °C followed by a decrease to an approximately constant level after 96 h. This is the first demonstration of the accumulation of sucrose as a second osmotically active carbohydrate in cyanobacteria.