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Haloarchaea and the formation of gas vesicles.

Pfeifer F - Life (Basel) (2015)

Bottom Line: Halophilic Archaea (Haloarchaea) thrive in salterns containing sodium chloride concentrations up to saturation.Their synthesis depends on environmental factors, such as light, oxygen supply, temperature and salt concentration.Except for GvpI and GvpH, all of these are required to form the gas permeable wall.

View Article: PubMed Central - PubMed

Affiliation: Microbiology and Archaea, Department of Biology, Technische Universität Darmstadt, Schnittspahnstrasse 10, 64287 Darmstadt, Germany. pfeifer@bio.tu-darmstadt.de.

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.

No MeSH data available.


Related in: MedlinePlus

Arrangement of gvp genes in p-vac of Hbt. salinarum PHH1 (a) and a comparison of the intergenic regions separating PD and PA (b). (a) The arrows depicting genes are colored as follows: dark green, encoding structural proteins of the A-J-M family and GvpC; light green, encoding accessory Gvp; red, encoding regulator proteins. Black arrows mark the start sites of transcription. (b) Comparison of the intergenic regions separating PA and PD in p-, mc- and c-vac. A 22-nt insertion occurs in c-vac adjacent to BRED. The 20-nt sequence required for GvpE-mediated activation is underlined (8-nt elements separated by 4 nt of unimportant sequences) in the case of UASA and marked by an arrow. Similar activation elements are found with UASD, pointing in the opposite direction. The TATA-box and BRE sequences (italics) are shaded in grey.
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life-05-00385-f002: Arrangement of gvp genes in p-vac of Hbt. salinarum PHH1 (a) and a comparison of the intergenic regions separating PD and PA (b). (a) The arrows depicting genes are colored as follows: dark green, encoding structural proteins of the A-J-M family and GvpC; light green, encoding accessory Gvp; red, encoding regulator proteins. Black arrows mark the start sites of transcription. (b) Comparison of the intergenic regions separating PA and PD in p-, mc- and c-vac. A 22-nt insertion occurs in c-vac adjacent to BRED. The 20-nt sequence required for GvpE-mediated activation is underlined (8-nt elements separated by 4 nt of unimportant sequences) in the case of UASA and marked by an arrow. Similar activation elements are found with UASD, pointing in the opposite direction. The TATA-box and BRE sequences (italics) are shaded in grey.

Mentions: The vac regions have been characterized for the Hbt. salinarum strains PHH1, NRC-1, SB3, GN101 and GRB [6,11,12,13]. The latter three strains are more recent natural isolates and genetically stable, whereas PHH1 (DSM 670) and NRC-1 (ATC 700922) are derived from strain collections and exhibit high mutation rates of Vac, Rub and Pum, due to the action of insertion (ISH) elements. The vac regions of PHH1 and NRC-1 were identified using the gvpA gene probe of the cyanobacterium, Calothrix [11,14]. This gene encodes the major gas vesicle structural protein, GvpA, and is highly conserved between bacterial and archaeal gas vesicle producers. Transformation experiments using the Vac− species, Hfx. volcanii, uncovered that gvpA is not sufficient for gas vesicle formation and that 12 additional gvp genes are required [13,15]. Furthermore, Vac− mutants of PHH1 (and NRC-1) are usually due to the integration of an ISH-element in a 9-kbp region surrounding gvpA [13]. The Vac− mutant strain, R1, whose genome sequence has been determined by the Oesterhelt Lab, incurred an ISH3 insertion upstream of p-gvpA, preventing the transcription [16]. Hbt. salinarum PHH1, R1 and NRC-1 all contain two different gvp gene clusters, p-vac (gvp1 in NRC-1) and c-vac (gvp2 in NRC-1), whereas SB3, GN101 and GRB contain the c-vac region only [6,12,17]. Expression of p-vac leads to spindle-shaped gas vesicles throughout growth, whereas the cylinder-shaped c-vac gas vesicles occur in the stationary growth phase only. The p-vac region is located on a plasmid and often incurs an ISH element. The 14 gvp genes constituting each vac region are arranged in the two oppositely oriented gene clusters, gvpACNO and gvpDEFGHIJKLM (Figure 2a). This arrangement is typical for p-vac and c-vac, but also for the mc-vac region of Hfx. mediterranei [6]. Hfx. mediterranei produces cylinder-shaped gas vesicles in the stationary growth phase when grown in 25% salt-media [18]. In contrast, twelve gvp genes in Hrr. vacuolatum and Hqr. walsbyi are arranged as the gvpACNO-FGHIJKLM gene cluster with additional DNA inserted between gvpO and gvpF in Hqr. walsbyi.


Haloarchaea and the formation of gas vesicles.

Pfeifer F - Life (Basel) (2015)

Arrangement of gvp genes in p-vac of Hbt. salinarum PHH1 (a) and a comparison of the intergenic regions separating PD and PA (b). (a) The arrows depicting genes are colored as follows: dark green, encoding structural proteins of the A-J-M family and GvpC; light green, encoding accessory Gvp; red, encoding regulator proteins. Black arrows mark the start sites of transcription. (b) Comparison of the intergenic regions separating PA and PD in p-, mc- and c-vac. A 22-nt insertion occurs in c-vac adjacent to BRED. The 20-nt sequence required for GvpE-mediated activation is underlined (8-nt elements separated by 4 nt of unimportant sequences) in the case of UASA and marked by an arrow. Similar activation elements are found with UASD, pointing in the opposite direction. The TATA-box and BRE sequences (italics) are shaded in grey.
© Copyright Policy
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC4390858&req=5

life-05-00385-f002: Arrangement of gvp genes in p-vac of Hbt. salinarum PHH1 (a) and a comparison of the intergenic regions separating PD and PA (b). (a) The arrows depicting genes are colored as follows: dark green, encoding structural proteins of the A-J-M family and GvpC; light green, encoding accessory Gvp; red, encoding regulator proteins. Black arrows mark the start sites of transcription. (b) Comparison of the intergenic regions separating PA and PD in p-, mc- and c-vac. A 22-nt insertion occurs in c-vac adjacent to BRED. The 20-nt sequence required for GvpE-mediated activation is underlined (8-nt elements separated by 4 nt of unimportant sequences) in the case of UASA and marked by an arrow. Similar activation elements are found with UASD, pointing in the opposite direction. The TATA-box and BRE sequences (italics) are shaded in grey.
Mentions: The vac regions have been characterized for the Hbt. salinarum strains PHH1, NRC-1, SB3, GN101 and GRB [6,11,12,13]. The latter three strains are more recent natural isolates and genetically stable, whereas PHH1 (DSM 670) and NRC-1 (ATC 700922) are derived from strain collections and exhibit high mutation rates of Vac, Rub and Pum, due to the action of insertion (ISH) elements. The vac regions of PHH1 and NRC-1 were identified using the gvpA gene probe of the cyanobacterium, Calothrix [11,14]. This gene encodes the major gas vesicle structural protein, GvpA, and is highly conserved between bacterial and archaeal gas vesicle producers. Transformation experiments using the Vac− species, Hfx. volcanii, uncovered that gvpA is not sufficient for gas vesicle formation and that 12 additional gvp genes are required [13,15]. Furthermore, Vac− mutants of PHH1 (and NRC-1) are usually due to the integration of an ISH-element in a 9-kbp region surrounding gvpA [13]. The Vac− mutant strain, R1, whose genome sequence has been determined by the Oesterhelt Lab, incurred an ISH3 insertion upstream of p-gvpA, preventing the transcription [16]. Hbt. salinarum PHH1, R1 and NRC-1 all contain two different gvp gene clusters, p-vac (gvp1 in NRC-1) and c-vac (gvp2 in NRC-1), whereas SB3, GN101 and GRB contain the c-vac region only [6,12,17]. Expression of p-vac leads to spindle-shaped gas vesicles throughout growth, whereas the cylinder-shaped c-vac gas vesicles occur in the stationary growth phase only. The p-vac region is located on a plasmid and often incurs an ISH element. The 14 gvp genes constituting each vac region are arranged in the two oppositely oriented gene clusters, gvpACNO and gvpDEFGHIJKLM (Figure 2a). This arrangement is typical for p-vac and c-vac, but also for the mc-vac region of Hfx. mediterranei [6]. Hfx. mediterranei produces cylinder-shaped gas vesicles in the stationary growth phase when grown in 25% salt-media [18]. In contrast, twelve gvp genes in Hrr. vacuolatum and Hqr. walsbyi are arranged as the gvpACNO-FGHIJKLM gene cluster with additional DNA inserted between gvpO and gvpF in Hqr. walsbyi.

Bottom Line: Halophilic Archaea (Haloarchaea) thrive in salterns containing sodium chloride concentrations up to saturation.Their synthesis depends on environmental factors, such as light, oxygen supply, temperature and salt concentration.Except for GvpI and GvpH, all of these are required to form the gas permeable wall.

View Article: PubMed Central - PubMed

Affiliation: Microbiology and Archaea, Department of Biology, Technische Universität Darmstadt, Schnittspahnstrasse 10, 64287 Darmstadt, Germany. pfeifer@bio.tu-darmstadt.de.

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.

No MeSH data available.


Related in: MedlinePlus