Gas vacuole development in a blue-green alga.

De novo productioni of gas vacutoles can be induced in the blue-green alga Nostoc muscorum by transferring the cells from a defined medium to distilled water. The unusual ultrastructure of the gas vacuole membranes permits their easy recognition when specimens are prepared for electron microscopy by freeze-etching. The youngest gas vacuoles are biconical organelles; 48 hours after induction the gas vacuoles reach their miaximum observed length when they are cylinders (1.5 by 0.1 micro) with cornical ends.