gas vesicles

Gas vesicles are thin, tube-like structures found in planktonic bacteria that allow the organisms to regulate their depth in water. Made of proteins, the vesicles are hollow and capped, dense enough to stop water from passing through but permeable to gases. The gas-filled vesicles create buoyancy, sending the bacteria toward the surface and sunlight, where photosynthesis can take place. Water pressure will collapse the vesicles, reducing buoyancy. Organisms with strong vesicles are better able to withstand higher water pressure, giving them an advantage over less-adaptable species.