Buoyancy regulation in light-limited continuous cultures of Microcystis aeruginosa

Microcystis aeruginosa was grown in light-limited continuous cultures at different growth rates on light-dark cycles at various photopenods. Due to the strength of the gas vesicles the organism was not able to collapse its gas vesicles by turgor pressure. Below the maximal growth rate, the organism was buoyant due to its high gas vesicle content. The results suggested that the rate of gas vesicle synthesis was not regulated. Upon a transition to high irradiance it took several hours before the cells lost their buoyancy due to polyglucan accumulation. The results are interpreted in an ecological context and it is suggested that Microcystis is an epilimnetic species due to its buoyancy regulation.