Structural determination of the exopolysaccharide of Pseudoalteromonas strain HYD 721 isolated from a deep-sea hydrothermal vent

Rougeaux, Hélène; Guézennec, Jean; Carlson, Russell W.; Kervarec, Nelly; Pichon, R.; Talaga, Philippe

doi:10.1016/s0008-6215(99)00019-1

Cited by 63 publications

(44 citation statements)

References 18 publications

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“…Sulfated polysaccharide production has been reported in only four bacterial genera to date, Sinorhizobium, Mycobacterium, Pseudoalteromonas, and now Mesorhizobium (10,42,53,56). Several Sinorhizobium species produce sulfated polysaccharides (10,22).…”

Section: Discussionmentioning

confidence: 99%

“…Finally, a bacterium isolated from a deep-sea hydrothermal vent, Pseudoalteromonas sp. strain HYD721, has also been reported to produce an exopolysaccharide on which a covalent sulfate modification adorns the 3Ј-hydroxyl group of mannose phosphate (56). The function of this sulfated exopolysaccharide has not been reported.…”

Section: Discussionmentioning

confidence: 99%

“…The production of sulfated cell surface polysaccharides is prevalent in eukaryotic cells but appears to be relatively rare in prokaryotes. To date, only three bacterial genera, Mycobacterium, Sinorhizobium, and Pseudoalteromonas, have been reported to contain sulfated polysaccharides (10,42,53,56). While the function of sulfated Nod factor is relatively well understood, the function of sulfated cell surface polysaccharides is poorly characterized.…”

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Mesorhizobium lotiProducesnodPQ-Dependent Sulfated Cell Surface Polysaccharides

2006

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Leguminous plants and bacteria from the family Rhizobiaceae form a symbiotic relationship, which culminates in novel plant structures called root nodules. The indeterminate symbiosis that forms between Sinorhizobium meliloti and alfalfa requires biosynthesis of Nod factor, a ␤-1,4-linked lipochitooligosaccharide that contains an essential 6-O-sulfate modification. S. meliloti also produces sulfated cell surface polysaccharides, such as lipopolysaccharide (LPS). The physiological function of sulfated cell surface polysaccharides is unclear, although mutants of S. meliloti with reduced LPS sulfation exhibit symbiotic abnormalities. Using a bioinformatic approach, we identified a homolog of the S. meliloti carbohydrate sulfotransferase, LpsS, in Mesorhizobium loti. M. loti participates in a determinate symbiosis with the legume Lotus japonicus. We showed that M. loti produces sulfated forms of LPS and capsular polysaccharide (KPS). To investigate the physiological function of sulfated polysaccharides in M. loti, we identified and disabled an M. loti homolog of the sulfate-activating genes, nodPQ, which resulted in undetectable amounts of sulfated cell surface polysaccharides and a cysteine auxotrophy. We concomitantly disabled an M. loti cysH homolog, which disrupted cysteine biosynthesis without reducing cell surface polysaccharide sulfation. Our experiments demonstrated that the nodPQ mutant, but not the cysH mutant, showed an altered KPS structure and a diminished ability to elicit nodules on its host legume, Lotus japonicus. Interestingly, the nodPQ mutant also exhibited a more rapid growth rate and appeared to outcompete wild-type M. loti for nodule colonization. These results suggest that sulfated cell surface polysaccharides are required for optimum nodule formation but limit growth rate and nodule colonization in M. loti.Most soils are limited in reduced forms of nitrogen. Thus, plants undergo symbioses with microorganisms that provide the plants with reduced nitrogen. The best studied of these symbioses occur between leguminous plants and a family of gram-negative bacteria known as rhizobia. The symbiosis culminates in the formation of novel structures on the plant root called nodules. To enter and colonize the nodules, the bacteria elicit a series of morphological changes in specialized epidermal cells called root hairs. The bacteria induce curling of the root hairs, trapping bacterial microcolonies in the center of the structure. The bacteria then elicit the formation of a plantderived tubular structure that emanates from the center of the curl, extending through the root hair and ultimately penetrating through the epidermis into the cortical layers of the root. This structure, known as an infection thread, is occupied by the bacteria and allows their entry into the interior of the root. The bacteria are released from the infection thread into the cytoplasm of plant cells within the nodule, where they differentiate into intracellular forms called bacteroids, which then reduce molecular dinitrogen for use...

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 99%

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Mesorhizobium lotiProducesnodPQ-Dependent Sulfated Cell Surface Polysaccharides

2006

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“…In recent years, the increasing demand for natural polymers for pharmaceutical, food, and other industrial applications has led to a remarkable interest in EPSs produced by marine bacteria (2). The structures and ecological roles of some bacterial EPSs from deep-sea hydrothermal vents and sediments have been reported (3)(4)(5)(6)(7). Most EPSs produced by marine bacteria are heteropolysaccharides consisting of 3 or 4 different monosaccharides that may be pentoses, hexoses, amino sugars, or uronic acids and are arranged in groups of 10 or less to form repeating units (8).…”

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Structure and Ecological Roles of a Novel Exopolysaccharide from the Arctic Sea Ice Bacterium Pseudoalteromonas sp. Strain SM20310

Liu

Chen

et al. 2013

Appl Environ Microbiol

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The structure and ecological roles of the exopolysaccharides (EPSs) from sea ice microorganisms are poorly studied. Here we show that strain SM20310, with an EPS production of 567 mg liter ؊1 , was screened from 110 Arctic sea ice isolates and identified as a Pseudoalteromonas strain. The EPS secreted by SM20310 was purified, and its structural characteristics were studied. The predominant repeating unit of this EPS is a highly complicated ␣-mannan with a molecular mass greater than 2 ؋ 10 6 Da. The backbone of the EPS consists of 2-␣-, 6-␣-mannosyl residues, in which a considerable part of the 6-␣-mannosyl residues are branched at the 2 position with either single t-mannosyl residues or two mannosyl residues. The structure of the described EPS is different from the structures of EPSs secreted by other marine bacteria. Analysis of the ecological roles of the identified EPS showed that the EPS could significantly enhance the high-salinity tolerance of SM20310 and improve the survival of SM20310 after freeze-thaw cycles. These results suggest that the EPS secreted by strain SM20310 enables the strain to adapt to the sea ice environment, which is characterized by low temperature, high salinity, and repeated freeze-thaw cycles. In addition to its functions in strain SM20310, this EPS also significantly improved the tolerance of Escherichia coli to freeze-thaw cycles, suggesting that it may have a universal impact on microorganism cryoprotection.

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“…In S. meliloti, the LPS undergoes an unusual covalent modification by sulfate (9,29). Al-though common in mammalian cells, sulfated carbohydrates appear to be rare in bacteria, having only been reported in S. meliloti (9), Mycobacterium (45,55), Mesorhizobium loti (62), and Pseudoalteromonas (56) to date. The physiological function of these sulfated molecules remains obscure, although mutants of S. meliloti and M. loti with decreased polysaccharide sulfation exhibit alterations in symbiosis (11,62; D. H. Keating, G. R. O. Campbell, and G. C. Walker, submitted for publication).…”

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Sinorhizobium meliloti SyrA Mediates the Transcriptional Regulation of Genes Involved in Lipopolysaccharide Sulfation and Exopolysaccharide Biosynthesis

Keating

2007

J Bacteriol

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Sinorhizobium meliloti is a gram-negative soil bacterium found either in free-living form or as a nitrogenfixing endosymbiont of leguminous plants such as Medicago sativa (alfalfa). S. meliloti synthesizes an unusual sulfate-modified form of lipopolysaccharide (LPS). A recent study reported the identification of a gene, lpsS, which encodes an LPS sulfotransferase activity in S. meliloti. Mutants bearing a disrupted version of lpsS exhibit an altered symbiosis, in that they elicit more nodules than wild type. However, under free-living conditions, the lpsS mutant displayed no change in LPS sulfation. These data suggest that the expression of lpsS is differentially regulated, such that it is transcriptionally repressed during free-living conditions but upregulated during symbiosis. Here, I show that the expression of lpsS is upregulated in strains that constitutively express the symbiotic regulator SyrA. SyrA is a small protein that lacks an apparent DNA binding domain and is predicted to be located in the cytoplasmic membrane yet is sufficient to upregulate lpsS transcription. Furthermore, SyrA can mediate the transcriptional upregulation of exo genes involved in the biosynthesis of the symbiotic exopolysaccharide succinoglycan. The SyrA-mediated transcriptional upregulation of lpsS and exo transcription is blocked in mutants harboring a mutation in chvI, which encodes the response regulator of a conserved two-component system. Thus, SyrA likely acts indirectly to promote transcriptional upregulation of lpsS and exo genes through a mechanism that requires the ExoS/ChvI twocomponent system.When nitrogen is limiting, leguminous plants enter into symbioses with members of the genera Rhizobium, Bradyrhizobium, Mesorhizobium, Azorhizobium, and Sinorhizobium (collectively called rhizobia) resulting in the formation of nodules. Within the nodule, differentiated cytoplasmic rhizobia called bacteroids reduce molecular dinitrogen to ammonia. Bacterial colonization of the nodule requires morphological alteration of epidermal cells called root hairs, resulting in the formation of a curled structure referred to as a shepherd's crook. Shepherd's crook formation is followed developmentally by the formation of an infection thread, a tubular ingrowth of the root hair that penetrates the plant. The infection thread is occupied by the bacteria, allowing their entry into the plant interior.

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Structural determination of the exopolysaccharide of Pseudoalteromonas strain HYD 721 isolated from a deep-sea hydrothermal vent

Cited by 63 publications

References 18 publications

Mesorhizobium lotiProducesnodPQ-Dependent Sulfated Cell Surface Polysaccharides

Mesorhizobium lotiProducesnodPQ-Dependent Sulfated Cell Surface Polysaccharides

Structure and Ecological Roles of a Novel Exopolysaccharide from the Arctic Sea Ice Bacterium Pseudoalteromonas sp. Strain SM20310

Sinorhizobium meliloti SyrA Mediates the Transcriptional Regulation of Genes Involved in Lipopolysaccharide Sulfation and Exopolysaccharide Biosynthesis

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