Halophilic Archaea (Haloarchaea) thrive in salterns containing sodium chloride 
concentrations up to saturation. Many Haloarchaea possess genes encoding gas 
vesicles, but only a few species, such as Halobacterium salinarum and Haloferax 
mediterranei, produce these gas-filled, proteinaceous nanocompartments. Gas 
vesicles increase the buoyancy of cells and enable them to migrate vertically in 
the water body to regions with optimal conditions. Their synthesis depends on 
environmental factors, such as light, oxygen supply, temperature and salt 
concentration. Fourteen gas vesicle protein (gvp) genes are involved in their 
formation, and regulation of gvp gene expression occurs at the level of 
transcription, including the two regulatory proteins, GvpD and GvpE, but also at 
the level of translation. The gas vesicle wall is solely formed of proteins with 
the two major components, GvpA and GvpC, and seven additional accessory proteins 
are also involved. Except for GvpI and GvpH, all of these are required to form 
the gas permeable wall. The applications of gas vesicles include their use as an 
antigen presenter for viral or pathogen proteins, but also as a stable 
ultrasonic reporter for biomedical purposes.