GAS VESICLE FORMATION IN THE DARK, AND IN LIGHT OF DIFFERENT IRRADIANCES, BY THE CYANOBACTERIUM MICROCYSTIS SP

Previous investigations with planktonic cyanobacteria have suggested that these organisms do not form new gas vesicles in the dark. This study, on Microcystis sp., confirmed that cells that had been preincubated at low photon irradiances (< 15 ųmol m- 2s-1) formed negligible amounts of gas vesicles in the dark. Significant gas vesicle formation occurred, however, in cells preincubated continuously at higher irradiances, and particularly within the range 65 to 105 ųmol m- 2s-1. The results suggest that gas vesicle formation in the dark is dependent on the prior accumulation of energy reserves. The amount of gas vesicles formed in continuous light was linearly related to irradiance over the range 0 to 20 ųmol m- 2s-1' and reached a maximum at only 30 ųmol m-2s-1that was over five times the amount formed at higher irradiances. This suggests that the rate of gas vesicle formation, regulated directly in response to irradiance, has a role in the light-mediated buoyancy regulation of this cyanobacterium. © 1990 The British Phycological Society.