Effects of Light and Potassium Ion on Buoyancy Regulation with Gas Vesicle in a Cyanobacterium Microcystis aeruginosa NIES-843

In this study, we confirmed the effects of light and K + concentration on the buoyancy of the cyanobacterium Microcystis aeruginosa (Kutzing) Lemmermann (NIES-843), and the relationship between the gas vesicle and buoyancy of M. aeruginosa was revealed through the culture experiment. The results showed that under laboratory conditions, light illumination and K + concentration strongly affected the flotation and settlement of M. aeruginosa , and that the floating and settling cycle of M. aeruginosa could be reproduced in a test tube by controlling light illuminance. The ability of M. aeruginosa buoyancy weakened with the increase in the K + concentration, and M. aeruginosa could not exhibit buoyancy at the K + concentration of 0.03 mol/L. The phase-contrast microscope observation revealed that M. aeruginosa that floated on the water surface had gas vesicles, while none of the gas vesicles was detected for M. aeruginosa at the bottom of a test tube.