Haloarchaea and the Formation of Gas Vesicles

Abstract

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.

Internal RNAs overlapping coding sequences can drive the production of alternative proteins in archaea

“…This putative intraRNA is related to an important H. salinarum gene, gvpC1 , which encodes for one of the gas vesicle structural proteins. Although extensively studied [51], there are no reports of transcripts equivalent to the intraRNA found here, probably because growing H. salinarum for such relatively long time was not usual until the gas vesicle release phenomenon was proposed [52]. Secondary structure prediction with different methods did not show evidence of structures that would generate dRNA-seq false positives (data not shown).…”

Anaerobic Metabolism in Haloferax Genus

“…Gas vesicles increase the buoyancy of cells and allow them to migrate vertically in the water body from low oxygen conditions to regions with optimal conditions to sustain microaerobic or aerobic growth (Pfeifer, 2015). Haloarchaeal gas vesicles consist of mainly one protein called GvpA, but their formation occurs along a complex pathway involving 14 different gvp genes, some of which regulate the process (Zimmermann & Pfeifer, 2004).…”

Microscopy of Microbial Gas Vesicles

“…salinarum is an extremely halophilic archaeon (Pfeifer, 2015). To harvest light energy, the species uses bacteriorhodopsin that forms crystalline purple patches in the cytoplasmic membrane (Pfeifer, 2015). Gas vesicle-containing cells show pink, opaque colonies on solid media due to the light-interacting properties of gas vesicles; however, cells without gas vesicles form red, transparent colonies (Fig.…”

“…Originally isolated as a contaminant from salted fish in 1919, Hbt. salinarum is an extremely halophilic archaeon (Pfeifer, 2015). To harvest light energy, the species uses bacteriorhodopsin that forms crystalline purple patches in the cytoplasmic membrane (Pfeifer, 2015).…”

“…Key Words: Buoyancy, Gas vesicle, Nanobubble, Protein shell be employed as an antigen presenter for viral or pathogen proteins (Pfeifer, 2015). This review focuses on the structure and microscopy of the most representative gas vesicles in microbes.…”