GLUCOSYLGLYCEROL ACCUMULATION DURING SALT ACCLIMATION OF 2 UNICELLULAR CYANOBACTERIA

A turbidostat culture technique was used to study the effects of different salt shocks on the freshwater cyanobacteria Synechocystis sp. strain PCC 6803 and Microcystis firma. Shocks were performed either suddenly or gradually, on both unacclimated cultures and those pre-acclimated to 0.77 M-NaCl. All suddenly shocked cultures exhibited a decline in growth after a few hours, characterized by severely decreased metabolic activities (e.g. photosynthesis, respiration, glucose-6-phosphate dehydrogenase activity) and a time course of restoration which coincided with the accumulation of glucosylglycerol. Additionally, all untreated cultures had a late (after a few days) growth depression, distinguished by the stagnation of cell division. This was overcome by physiological adaptation of the whole cells or selection of cells with superior salt tolerance. The different types of growth depressions and the unique pattern of glucosylglycerol accumulation led to the conclusion that glucosylglycerol was necessary to maintain metabolic processes, but that this alone cannot account for successful salt acclimation.