Glycerol metabolism in the extremely halophilic bacterium<i>Salinibacter ruber</i>

Sher, Jonathan P.; Elevi, Rahel; Mana, Lily; Oren, Aharon

doi:10.1016/s0378-1097(04)00077-1

Cited by 38 publications

(25 citation statements)

References 23 publications

(46 reference statements)

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“…3). The specific activity of glycerol kinase in parent strain H26 grown in the presence of glycerol was measured as 430 Ϯ 30 nmol ⅐ min ), and H. volcanii (31 nmol ⅐ min Ϫ1 mg Ϫ1 for cells grown in complex medium with peptides), determined in similar assays (20,23,25), this value was within a reasonable range of measurement for glycerol kinase enzymes.…”

Section: Resultsmentioning

confidence: 62%

“…Negative control mixtures lacked ATP or glycerol, or the reactions were performed using boiled cell lysate from the parent strain H26. Samples (0.45 ml) were withdrawn at 10, 20, 30 35, 40, 45, 50, 60, and 90 min after the start of the reaction, which was terminated by the addition of 0.45 ml of 0.2 N H 3 PO 4 , and the reaction mixture was used to measure the formation of glycerol-3-phosphate with rabbit muscle glycerol-3-phosphate dehydrogenase as described previously (23).…”

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confidence: 99%

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Glycerol-Mediated Repression of Glucose Metabolism and Glycerol Kinase as the Sole Route of Glycerol Catabolism in the Haloarchaeon Haloferax volcanii

2009

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Although glycerol is the primary carbon source available to halophilic heterotrophic communities, little is known regarding haloarchaeal glycerol metabolism. In this study, a gene encoding a glycerol kinase homolog (glpK; HVO_1541) was deleted from the genome of the haloarchaeon Haloferax volcanii by a markerless knockout strategy. The glpK mutant, KS4, readily grew on yeast extract-peptone complex medium and glucose minimal medium but was incapable of growth on glycerol. Glycerol kinase activity was dependent on the glpK gene and readily detected in cells grown on glucose and/or glycerol, with the activity level higher in medium supplemented with glycerol (with or without glucose) than in medium with glucose alone. An analysis of carbon utilization revealed that glycerol suppressed the metabolism of glucose in both the parent H26 and glpK mutant strains, with catabolite repression more pronounced in the glycerol kinase mutant. Transcripts specific for glpK and an upstream gene, gpdA, encoding a homolog of glycerol-3-phosphate dehydrogenase subunit A, were upregulated (8-and 74-fold, respectively) in the presence of glycerol and glucose compared to those in the presence of glucose alone. Furthermore, glpK was transcriptionally linked to the gpdC gene of the putative glycerol-3-phosphate dehydrogenase operon (gpdABC), based on the findings of reverse transcriptase PCR analysis. The results presented here provide genetic and biochemical evidence that glycerol metabolism proceeds through a glycerol kinase encoded by glpK and suggest that a glycerol-3-phosphate dehydrogenase encoded by the upstream gpdABC operon is also involved in this pathway. Furthermore, our findings reveal a unique example of glycerol-induced repression of glucose metabolism in H. volcanii.Halophilic and halotolerant microorganisms have adapted different methods for withstanding the high osmotic pressure exerted by their surrounding hypersaline environment. Halophilic archaea (7, 13), as well as the halophilic bacterium Salinibacter ruber (19), maintain a high intracellular salt concentration by accumulating K ϩ and Cl Ϫ ions and excluding Na ϩ ions, thus requiring intracellular proteins to be active under high-salt conditions. Many halophilic bacteria (24), the halotolerant green alga Dunaliella sp. (3), and some haloarchaea (12) exclude cytoplasmic salts and rely on organic solutes such as ectoine, glycine betaine, and glycerol to provide osmotic balance. Glycerol, in particular, is accumulated in molar quantities by Dunaliella as an organic osmotic solute. Due to leakage from healthy Dunaliella cells (1, 3, 26) and/or cellular lysis, glycerol is released into the surrounding environment, where it serves as a primary energy source for haloarchaea. Upon uptake, halophilic microorganisms assimilate glycerol into dihydroxyacetone phosphate (DHAP) by one of two catabolic routes (Fig. 1). In one route, glycerol is first phosphorylated by glycerol kinase to form sn-glycerol-3-phosphate, which is subsequently oxidized by sn-glycerol-3-phosphate dehy...

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Section: Resultsmentioning

confidence: 62%

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confidence: 99%

Glycerol-Mediated Repression of Glucose Metabolism and Glycerol Kinase as the Sole Route of Glycerol Catabolism in the Haloarchaeon Haloferax volcanii

2009

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“…The above-cited microautoradiography study failed to show incorporation of glycerol into Salinibacter cells in the saltern community (Rosselló-Mora et al 2003), and the species description of Salinibacter ruber states that glycerol does not stimulate growth (Antón et al 2002). However, later studies have demonstrated that glycerol is metabolized by Salinibacter: part of the substrate is respired as CO 2 , part is incorporated into cell material (Sher et al 2004), and part is incompletely oxidized to a soluble product, which was later identified as dihydroxyacetone (Elevi Bardavid & Oren 2008b). The discrepancies between the results obtained in these different studies may well be due to the different methodologies used and the different incubation periods involved.…”

Section: Discussionmentioning

confidence: 99%

Community respiration studies in saltern crystallizer ponds

Warkentin¹,

Schumann²,

Oren³

2009

Aquat. Microb. Ecol.

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To measure community respiration by the heterotrophic Archaea (dominated by Haloquadratum) and Bacteria (Salinibacter) in the NaCl-saturated crystallizer brines of the solar salterns in Eilat, Israel, and to obtain information on the substrates preferred by the community as energy sources, we used 2 complementary approaches: monitoring of changes in oxygen concentration using planar optode sensors in short (up to 30 min) experiments, and long-term (up to 40-50 h) incubations using Winkler titration to assess changes in oxygen levels. Respiration rates measured were ~3 fmol cell -1 h -1. Respiration was markedly stimulated by glycerol, dihydroxyacetone and pyruvate, but not by yeast extract, succinate, and fumarate. These findings are discussed in view of genomic information on the dominant heterotrophic organisms in the community as well as the outcome of earlier studies on the behavior of halophilic prokaryotes in situ and in laboratory cultures. Despite the low in situ respiration rate, the oxygen uptake studies added information on the activities of the heterotrophic communities in salt-saturated ecosystems and on the substrates metabolized by the microorganisms present.

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“…Cell integrity requires high salt concentrations in both cases, and growth only occurs at Ͼ2 M NaCl. Both Salinibacter and the haloarchaea are aerobic heterotrophs that exploit the large stock of organic nutrients produced in previous stages of seawater concentration, mostly by the green alga Dunaliella, and they use a similar range of organic compounds as carbon and energy sources (5). Like haloarchaea, Salinibacter contains a high proportion of carotenoids in its membrane, producing red colonies of similar appearance (2).…”

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The genome of Salinibacter ruber : Convergence and gene exchange among hyperhalophilic bacteria and archaea

Mongodin

Nelson

Daugherty

et al. 2005

Proc. Natl. Acad. Sci. U.S.A.

285

259

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Saturated thalassic brines are among the most physically demanding habitats on Earth: few microbes survive in them. Salinibacter ruber is among these organisms and has been found repeatedly in significant numbers in climax saltern crystallizer communities. The phenotype of this bacterium is remarkably similar to that of the hyperhalophilic Archaea (Haloarchaea). The genome sequence suggests that this resemblance has arisen through convergence at the physiological level (different genes producing similar overall phenotype) and the molecular level (independent mutations yielding similar sequences or structures). Several genes and gene clusters also derive by lateral transfer from (or may have been laterally transferred to) haloarchaea. S. ruber encodes four rhodopsins. One resembles bacterial proteorhodopsins and three are of the haloarchaeal type, previously uncharacterized in a bacterial genome. The impact of these modular adaptive elements on the cell biology and ecology of S. ruber is substantial, affecting salt adaptation, bioenergetics, and photobiology.halophile ͉ lateral gene transfer ͉ convergence ͉ prokaryotic evolution ͉ rhodopsins U ntil recently, halophilic archaea (haloarchaea) were thought to be the only cells capable of thriving in saltern crystallizers. These impoundments contain Ϸ37% NaCl, at the limits of tolerance for this environmental factor. Further concentration of thalassic (seawater-derived) hypersaline water leads to precipitation of magnesium salts and sterility. Fluorescent in situ hybridization indicates that one crystallizer morphotype, well defined large rods, corresponds to a bacterium of the Cytophaga cluster (1), within the Bacteroides͞Chlorobi group. This organism represents 10-20% of the cells in climax crystallizer communities (spring and summer in temperate latitudes). Representative strains (as defined by 16S rRNA sequences) have been isolated from the same environment and described as the previously uncharacterized genus and species Salinibacter ruber (2).The closest cultivated relative of S. ruber (henceforth Salinibacter) is Rhodothermus marinus (89% 16S rRNA sequence similarity), a slightly halophilic thermophile isolated from marine hot springs (2). Salinibacter displays many remarkable similarities to haloarchaea, one being a very high concentration of potassium in the cytoplasm (3). This property is associated, as in haloarchaea, with a high content of acidic amino acids and a low content of hydrophobic residues in bulk protein, necessary for protein solubility at such high ionic strength (4). Cell integrity requires high salt concentrations in both cases, and growth only occurs at Ͼ2 M NaCl. Both Salinibacter and the haloarchaea are aerobic heterotrophs that exploit the large stock of organic nutrients produced in previous stages of seawater concentration, mostly by the green alga Dunaliella, and they use a similar range of organic compounds as carbon and energy sources (5). Like haloarchaea, Salinibacter contains a high proportion of carotenoids in its membrane, pro...

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Glycerol metabolism in the extremely halophilic bacteriumSalinibacter ruber

Cited by 38 publications

References 23 publications

Glycerol-Mediated Repression of Glucose Metabolism and Glycerol Kinase as the Sole Route of Glycerol Catabolism in the Haloarchaeon Haloferax volcanii

Glycerol-Mediated Repression of Glucose Metabolism and Glycerol Kinase as the Sole Route of Glycerol Catabolism in the Haloarchaeon Haloferax volcanii

Community respiration studies in saltern crystallizer ponds

The genome of Salinibacter ruber : Convergence and gene exchange among hyperhalophilic bacteria and archaea

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