Figure 1.

Colonies (a) and cells of Halobacterium (Hbt.) salinarum producing gas vesicles (b,c). (a) Colonies on solid media grown for one week at 40 °C and three weeks at room temperature. Vesicle (Vac⁺) cells form pink white colonies, whereas colonies of Vac⁻ mutants are red and transparent. (b) Cells grown in liquid media observed by phase-contrast light microscopy. (c) Cells of a Vac⁺ colony investigated by transmission electron microscopy. The pleomorphic shape of the cells grown for three months on solid media differs from the rod-shaped cells seen in liquid culture.