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A strain Leuconostoc citreum B-2 was isolated from homemade fermentation product of pineapple and its polysaccharide yield was 28.3 g/L after cultivating the strain in Man-Rogosa-Sharpe (MRS) medium with 75 g/L sucrose. The exopolysaccharide (EPS) was characterized by gas chromatography (GC), Fourier-transform infrared (FT-IR) spectra, high-performance size-exclusion chromatography (HPSEC), nuclear magnetic resonance (NMR) spectroscopy and scanning electron microscope (SEM) analysis in present study. The monosaccharide composition of EPS was glucose and molecular weight was 3.77 × 10 6 Da. FT-IR and NMR spectra revealed that the B-2 EPS was composed of 75% α-(1 → 6) linked d -glucopyranose units existing in the main chain with 19% α-(1 → 3) branching and only a few α-(1 → 2) branching. The SEM of the dried EPS appeared irregular sheets with glittering surface and compact structure. Water solubility index and water holding capacity of B-2 EPS were 80% and 450%, respectively. All the mentioned characteristics suggested that the EPS has a potential application in the food, cosmetic and pharmaceuticals industry. [ABSTRACT FROM AUTHOR]

Carbon dioxide sequestering bacterial strains were previously isolated from free air CO 2 enriched (FACE) soil. In the present study, these strains were screened for PHA accumulation and Bacillus cereus SS105 was found to be the most prominent PHA accumulating strain on sodium bicarbonate and molasses as carbon source. This strain was further characterized by Spectrofluorometric method and Confocal microscopy after staining with Nile red. PHA granules in inclusion bodies were visualized by Transmission Electron Microscopy. The PHA and its monomer composition were characterized by GC–MS followed by FTIR and NMR. The genetic basis of PHA production was confirmed by the amplification, cloning and analysis of PHA biosynthesis genes phaR, phaB and phaC from B. cereus with the degenerate primers . The PHA production was further optimized by Response Surface Methodology and the percent increase observed after optimization was 55.16% (w/v). [ABSTRACT FROM AUTHOR]

Here, we describe a simple, non-time consuming and inexpensive method for monitoring of Calcofluor white M2R-binding exopolysaccharides in individual bacterial cells. This method was demonstrated by time-lapse microscopy of succinoglycan-producing cells of the plant-symbiotic alpha-proteobacterium Sinorhizobium meliloti . The method is most likely applicable to other bacteria producing β-(1 → 3) and β-(1 → 4) linked polysaccharides. [ABSTRACT FROM AUTHOR]

A novel exopolysaccharide (EPS), promisingly served as natural alternatives of commercial additives, was obtained from a culture of Lactobacillus plantarum KX041 , a specie of lactic acid bacteria (LAB) regarded as Generally Recognized as Safe Foods (GRAS). However, the low yield severely hindered further study and application of the EPS. The influences of medium components and culture conditions were investigated and the optimal conditions of the EPS production were successfully obtained by response surface methodology (RSM). Maximum EPS production 599.52 mg/mL (about 3 folds than the original production) was obtained at optimal conditions of soybean peptone (20 g/L), fermentation temperature (35 °C) and initial pH (6.38). The EPS had a molecular weight of 38.67 KDa and it consisted of arabinose, mannose, glucose and galactose in a molar ratio of 0.95:12.94:7.26:3.31. A specific spectrogram of neutral polysaccharide was obtained by FT-IR analysis, and the EPS also exhibited higher thermal stability with a degradation temperature of 289.01 °C in DSC analysis. A comprehensive investigation of antioxidant activity in vitro indicated that the EPS possessed superior antioxidant activity with the EC 50 value of ABTS, DPPH, hydroxyl and superoxide free radical scavenging were 0.2, 1.4, 1.7 and 5.6 mg/mL, respectively. Furthermore, combined with reducing power analysis, it suggested that the EPS not only acted as electrons donor to directly react with free radicals, but also exerted antioxidant activity with other mechanisms which need to be studied further. All these results collectively shown that as a natural compound, the EPS produced by Lactobacillus plantarum KX041 had a great potential to be developed as natural antioxidants or functional additive in food industry. [ABSTRACT FROM AUTHOR]

The exopolysaccharide succinoglycan is produced mainly by a large number of soil microbes of Agrobacterium, Rhizobium or Pseudomonas genera etc. Structural properties of succinoglycan are unique in terms of its thermal stability and superior viscosifying property. Unlike the other highly commercialized bacterial exopolysaccharides like dextran or xanthan, mass scale application of succinoglycan has not been that much broadly explored yet. Bacterial succinoglycan is found suitable as a viscosifying and emulsifying agent in food industry, in gravel packing or fluid-loss control agent etc. In this present review, the key aspects of succinoglycan study, in particular, developments in structural characterizations, exo/ exs operon system involved in biosynthesis pathway, commercial applications in food and other industries and patenting trends have been discussed. [ABSTRACT FROM AUTHOR]

Exopolysaccharides play an important role in the physiology of a bacterial cell. Ensifer meliloti is capable of producing at least two types of exopolysaccharides (EPS): succinoglycan and galactoglucan. In E. meliloti, EPS are best known for their role in mediating interaction with its symbiotic hosts. It was previously shown that high concentrations of Mg2+ or K+ were capable of suppressing the mucoid phenotype associated with galactoglucan production in an expR+ derivative of Rm1021. In an attempt to determine how Mg2+ regulates galactoglucan production, SRmD363 was mutagenised and screened for mutants which were visibly mucoid at high concentrations of magnesium. Tn5 mutations in genes exoX, emmB, phoC and SMc00722 were isolated. SMc00722 is annotated as a hypothetical transmembrane protein that is conserved in the α-proteobacteria. Characterisation of SMc00722 in Rm1021 showed that the increased mucoidy was due to succinoglycan. Strains carrying mutations in SMc00722 showed increased biofilm production, and were more sensitive to high Mg2+ concentrations and deoxycholate. In addition, we show that strains carrying a mutation in SMc00722 have elevated intracellular Mg2+ concentrations. Taken together, the data are consistent with the hypothesis that SMc0722 may play a role in maintaining intracellular magnesium concentration, and we suggest that this gene be tentatively annotated as mhrA (magnesium homeostasis related). [ABSTRACT FROM AUTHOR]

An exopolysaccharide (EPS) producing strain CAS grown in a Bushnell Haas medium was isolated from curd sample and identified as Rhizobium radiobacter CAS. The biopolymer was duly characterized by FT-IR and NMR spectroscopy and was found to be composed of glucose and galactose in a molar ratio of 6.99:1 as confirmed by HPAEC; thus depicting it to be succinoglycan type exopolysaccharide. In addition, conceivable presence of one succinate and two acetate groups of succinoglycan was estimated using 1 H NMR analysis by specific signal integration. Furthermore, as a documented fact, the insights into the rheological behaviors portray phenomenal influences in food, cosmetics and pharmaceutical industries as thickening, gelling, stabilizing and emulsifying agent. However, this piece of information has remained unnoticed from the existing literature. Thus, in the present study the rheological properties of succinoglycan type biopolymer in aqueous solution were systematically investigated. The flow behaviour testing in an aqueous solution verified its pseudoplastic character and higher apparent viscosity. Furthermore, study on its potential strength and tolerance in various thermal conditions, cation salts, and pH has been studied in depth. Such a study can provide a thorough guidance on the rheological behaviour of the biomaterial and thus impart significant insights into postulating its application spectrum into food, cosmetics and pharmaceutical industrial sectors. The present study is thus, one of its kinds which decipher the complete rheological behavioural portrait. [ABSTRACT FROM AUTHOR]

Literature interpretations of the electrophoretic mobility of spherical polyelectrolytes are revisited using the capillary-electrophoresis data of Duval et al. (2006) for the extracellular polysaccharide succinoglycan as an example. Subtle changes in the polyelectrolyte mobility have recently been attributed to new electrokinetic theories that feature multi-component electrolytes, charge regulation, and the so-called polarization and relaxation phenomena. However, these calculations exhibit several unusual trends that have yet to be explained, and so the conclusions drawn from them are controversial. Here, independent computations strengthen conclusions drawn from the original model of Duval et al., i.e., the discrepancies between experiments and all the presently available electrokinetic theories reflect changes in the conformation of succinoglycan arising from changes in the electrolyte pH and ionic strength. [ABSTRACT FROM AUTHOR]

Agrobacterium is a genus of gram-negative bacteria that can produce several typical exopolysaccharides with commercial uses in the food and pharmaceutical fields. In particular, succinoglycan and curdlan, due to their good quality in high yield, have been employed on an industrial scale comparatively early. Exopolysaccharide biosynthesis is a multiple-step process controlled by different functional genes, and various environmental factors cause changes in exopolysaccharide biosynthesis through regulatory mechanisms. In this mini-review, we focus on the genetic control and regulatory mechanisms of succinoglycan and curdlan produced by Agrobacterium. Some key functional genes and regulatory mechanisms for exopolysaccharide biosynthesis are described, possessing a high potential for application in metabolic engineering to modify exopolysaccharide production and physicochemical properties. This review may contribute to the understanding of exopolysaccharide biosynthesis and exopolysaccharide modification by metabolic engineering methods in Agrobacterium. [ABSTRACT FROM AUTHOR]

Detection methods for heavy metals are important and highly required due to their toxicity to the health of humans and the environment. Hence, using a polydiacetylene (PDA)-based sensoring bead, the presence of barium ions is exclusively detected for the first time. The sensoring platform has been designed as a PDA vesicle functionalized with a succinoglycan octasaccharide subunit serving as a metal coordination ligand. First, the succinoglycan octasaccahride subunit is isolated from Sinorhizobium meliloti, successfully conjugated to pentacosa-10,12-diynoic acid via reductive amination, and the functionalized vesicle system is investigated for color and fluorescence changes targeting nine different metal ions. To further improve the long-term storage stability and convenient handling of the vesicle detection system, the sensory vesicle is immobilized on millimeter-sized alginate beads through the ionotropic gelation method. This study provides an opportunity to design and develop various carbohydrate-based sensor materials. [ABSTRACT FROM AUTHOR]

Bacterial surface components and extracellular compounds, particularly flagella, lipopolysaccharides (LPSs), and exopolysaccharides (EPSs), in combination with environmental signals and quorum-sensing signals, play crucial roles in bacterial autoaggregation, biofilm development, survival, and host colonization. The nitrogen-fixing species Sinorhizobium meliloti (S. meliloti) produces two symbiosis-promoting EPSs: succinoglycan (or EPS I) and galactoglucan (or EPS II). Studies of the S. meliloti/alfalfa symbiosis model system have revealed numerous biological functions of EPSs, including host specificity, participation in early stages of host plant infection, signaling molecule during plant development, and (most importantly) protection from environmental stresses. We evaluated functions of EPSs in bacterial resistance to heavy metals and metalloids, which are known to affect various biological processes. Heavy metal resistance, biofilm production, and co-culture were tested in the context of previous studies by our group. A range of mercury (Hg II) and arsenic (As III) concentrations were applied to S. meliloti wild type strain and to mutant strains defective in EPS I and EPS II. The EPS production mutants were generally most sensitive to the metals. Our findings suggest that EPSs are necessary for the protection of bacteria from either Hg (II) or As (III) stress. Previous studies have described a pump in S. meliloti that causes efflux of arsenic from cells to surrounding culture medium, thereby protecting them from this type of chemical stress. The presence of heavy metals or metalloids in culture medium had no apparent effect on formation of biofilm, in contrast to previous reports that biofilm formation helps protect various microorganism species from adverse environmental conditions. In co-culture experiments, EPS-producing heavy metal resistant strains exerted a protective effect on AEPS-non-producing, heavy metal-sensitive strains; a phenomenon termed "rescuing" of the non-resistant strain. [ABSTRACT FROM AUTHOR]

The aim of the work was to optimize the combination of two strains of Streptococcus thermophilus used as a starter culture to develop a reduced-fat soft cheese with improved texture and added bio-value. Two strains, St 907 and St 399, were selected for the ability to produce exopolysaccharides (EPS) in milk. Biochemical characterization of EPS showed that the two biopolymers were similar in monosaccharide composition (glucose, galactose, rhamnose and mannose) but different in the relative molar ratio of the monomers and in molecular weight. St 907 produced a long chain and stringy EPS with very high water holding capacity, whereas St 399 produced a smaller-sized EPS, acting as texture enhancer. The strain St 399 was also selected as a major folic acid producer. The cheese obtained had 69.3% of moisture, 18.1% of proteins and 11.5% of fat. Despite the high level of hydration, the structure of the cheese was preserved and the low fat content was successfully compensated by EPS, which gave a positive effect on mouthfeel and cheese yield. The optimized formulation of the starter culture significantly increased the content of folates by up to 67% compared to control cheeses obtained using a commercial starter culture for soft cheeses. [ABSTRACT FROM AUTHOR]

Succinoglycans are heteropolysaccharides synthesized by bacteria. It possesses thickening and texturizing properties, making it useful in a number of applications in food, pharmaceutical and chemical industries. Agrobacterium radiobacter NBRC 12665 cells were immobilized in the loofa sponge matrix and used to produce succinoglycan. Production of the biopolymer using the substrates sugar cane molasses, sucrose, glucose and lactose at concentrations of 2.5%, 5.0% and 7.5% for eight days was analyzed. The best results were obtained using sugar cane molasses (14.0 g/L) and lactose (12 g/L) at 7.5% with immobilized cells. Under optimum conditions, it was possible to re-use the matrix to produce succinoglycan in five consecutive eight day operating cycles. Scanning electron microscopy and Fourier Transform Infrared Spectroscopy (FTIR) confirmed the immobilization of the microorganism in the loofa sponge. FTIR of the biopolymer revealed the presence of residues of carbohydrate and carboxylic groups. The use of mixed ions exchange resin for removal of the succinoglycan pigments from molasses resulted in a depigmentation of 74% in the color of the biopolymer and 65% in its turbidity. Succinoglycans obtained from lactose and sugar cane molasses exhibited molecular weights of 2.734 × 10 6 g/mol and 2.326 × 10 6 g/mol, respectively. Rheological analysis of the succinoglycans in terms of concentration (0.5–2.0%), temperature (5–75 °C) and pH (2.5–10.0) revealed non-Newtonian and shear thinning behavior of the biopolymer. The technique of immobilization in loofa sponge and use of sugar cane molasses as a low cost carbon source produced significant and effective results for the industrial production of succinoglycan. [ABSTRACT FROM AUTHOR]

Flavonoids are a group of plant secondary metabolites including polyphenolic molecules, and they are well known for antioxidant, anti-allergic, anti-inflammatory and anti-viral propertied. In general, flavonoids are detected with various non-colorimetric detection methods such as column liquid chromatography, thin-layer chromatography, and electrochemical analysis. For the first time, we developed a straightforward colorimetric detection system allowing recognition of some highly hydrophobic flavonoids such as alpha-naphthoflavone and beta-naphthoflavone, visually using 10,12-pentacosadiynoic acid (PCDA) derivatized with succinoglycan monomers isolated from Sinorhizobium meliloti. Besides changes in visible spectrum, we also demonstrate fluorescence changes using our detection system in the presence of those flavonoids. The succinoglycan monomers attached to PCDA molecules may function as an unstructured molecular capturer for some highly hydrophobic flavonoids by hydrophobic interactions, and transmit their molecular interactions as a color change throughout the PCDA liposome. [ABSTRACT FROM AUTHOR]

Both bacterial symbionts and pathogens rely on their host-sensing mechanisms to activate the biosynthetic pathways necessary for their invasion into host cells. The Gram-negative bacterium Sinorhizobium meliloti relies on its RSI (ExoR-ExoS-ChvI) Invasion Switch to turn on the production of succinoglycan, an exopolysaccharide required for its host invasion. Recent whole-genome sequencing efforts have uncovered putative components of RSI-like invasion switches in many other symbiotic and pathogenic bacteria. To explore the possibility of the existence of a common invasion switch, we have conducted a phylogenomic survey of orthologous ExoR, ExoS, and ChvI tripartite sets in more than ninety proteobacterial genomes. Our analyses suggest that functional orthologs of the RSI invasion switch co-exist in Rhizobiales, an order characterized by numerous invasive species, but not in the order’s close relatives. Phylogenomic analyses and reconstruction of orthologous sets of the three proteins in Alphaproteobacteria confirm Rhizobiales-specific gene synteny and congruent RSI evolutionary histories. Evolutionary analyses further revealed site-specific substitutions correlated specifically to either animal-bacteria or plant-bacteria associations. Lineage restricted conservation of any one specialized gene is in itself an indication of species adaptation. However, the orthologous phylogenetic co-occurrence of all interacting partners within this single signaling pathway strongly suggests that the development of the RSI switch was a key adaptive mechanism. The RSI invasion switch, originally found in S. meliloti, is a characteristic of the Rhizobiales, and potentially a conserved crucial activation step that may be targeted to control host invasion by pathogenic bacterial species. [ABSTRACT FROM AUTHOR]

Protonic currents play a vital role in electrical signalling in living systems. It has been suggested that succinoglycan plays a specific role in alfalfa root nodule development, presumably acting as the signaling molecules. In this regard, charge transport and proton dynamics in the biopolymer exopolysaccharide succinoglycan have been studied by means of electrical measurements and nuclear magnetic resonance (NMR) spectroscopy. In particular, a dielectric dispersion in the system has revealed that the electrical conduction is protonic rather electronic. Besides, our laboratory- and rotating-frame ¹H NMR measurements have elucidated the nature of the protonic conduction, activation of the protonic motion being associated with a glass transition. [ABSTRACT FROM AUTHOR]

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Highlights: [•] Low-molecular-weight succinoglycans from Sinorhizobium meliloti complexed with pindolol. [•] Complex formation was confirmed by various instrumental methods. [•] Linear succinoglycans enhanced pindolol solubility much better than cyclodextrin. [•] Low-molecular-weight succinoglycans were suggested as the best solubilizer for pindolol. [ABSTRACT FROM AUTHOR]

Highlights: [•] The purified rhizobial carbohydrates were monofuntionalized with biotin tag. [•] The biotinylated cyclic β-glucans were synthesized through four steps. [•] Succinoglycans and monomers were biotinylated at the reducing sugar with one step. [•] The prepared neoglycoconjugate will be solid probes for study on symbiotic activity. [Copyright &y& Elsevier]

Sinorhizobium meliloti requires exopolysaccharides in order to form a successful nitrogen-fixing symbiosis with Medicago species. Additionally, during early stages of symbiosis, S. meliloti is presented with an oxidative burst that must be overcome. Levels of production of the exopolysaccharides succinoglycan (EPS-I) and galactoglucan (EPS-II) were found to correlate positively with survival in hydrogen peroxide (H2O2). H2O2 damage is dependent on the presence of iron and is mitigated when EPS-I and EPS-II mutants are cocultured with cells expressing either exopolysaccharide. Purified EPS-I is able to decrease in vitro levels of H2O2, and this activity is specific to the symbiotically active low-molecular-weight form of EPS-I. This suggests a potential protective function of exopolysaccharides against H2O2 during early symbiosis. [ABSTRACT FROM AUTHOR]

Rhizobia establish a symbiotic relationship with their host legumes to induce the formation of nitrogen-fixing nodules. This process is regulated by many rhizobium regulators, including some two-component regulatory systems (TCSs). NtrY/NtrX, a TCS that was first identified in Azorhizobium caulinodans, is required for free-living nitrogen metabolism and symbiotic nodulation on Sesbania rostrata. However, its functions in a typical rhizobium such as Sinorhizobium meliloti remain unclear. Here we found that the S. meliloti response regulator NtrX but not the histidine kinase NtrY is involved in the regulation of exopolysaccharide production, motility, and symbiosis with alfalfa. A plasmid insertion mutant of ntrX formed mucous colonies, which overproduced succinoglycan, an exopolysaccharide, by upregulating its biosynthesis genes. This mutant also exhibited motility defects due to reduced flagella and decreased expression of flagellins and regulatory genes. The regulation is independent of the known regulatory systems of ExoR/ExoS/ChvI, EmmABC, and ExpR. Alfalfa plants inoculated with the ntrX mutant were small and displayed symptoms of nitrogen starvation. Interestingly, the deletion mutant of ntrY showed a phenotype similar to that of the parent strain. These findings demonstrate that the S. meliloti NtrX is a new regulator of succinoglycan production and motility that is not genetically coupled with NtrY. [ABSTRACT FROM AUTHOR]

Sinorhizobium meliloti NRG247 has a Fix+ phenotype on Medicago truncatula A20 and is Fix- on M. truncatula A17, and the phenotype is reversed with S. meliloti NRG185. As the succinoglycan was shown to impact host specificity, an analysis of the succinoglycan oligosaccharides produced by each strain was conducted. The symbiotically active succinoglycan trimeric oligosaccharides (STOs) from the two S. meliloti strains were compared by chromatography and mass spectrometry, and the analysis of the S. meliloti NRG247 oligosaccharides showed that this strain produces an abundance of STO trimer 1 (Tl), containing no succinate (i.e., three nonsuccinylated repeats), yet the low-molecular-weight pool contained no nonsuccinylated monomers (potential repeats). This showed that STO Tl is likely to be the active signal on M. truncatula A20 and that the biosynthesis of the STOs is not a random polymerization of the monomer population. The results also suggest that the fully succinylated STO T7 is required for the infection of M. truncatula A17. [ABSTRACT FROM AUTHOR]

Iron is an essential nutrient for nitrogen-fixing legume root nodules, and the chelation of ferrous iron plays an important role in the mobility and availability of iron to the legume. In the present study, we investigated the iron-binding properties of low-molecular weight succinoglycans isolated from the nitrogen-fixing bacterium, Sinorhizobium meliloti. The low-molecular weight succinoglycans comprising three monomers (M1-M3), four dimers (D1-D4), and six trimers (T1-T6) of the succinoglycan repeating unit were purified by various chromatographic techniques. Interestingly, the colorimetric ferrozine method showed that the succinoglycans T6, M3, and D3 demonstrated a ferrous iron chelating ability of 83, 63, and 38 % per mg, respectively. The individual binding constants were determined as 43703, 2313, and 760 M for succinoglycans T6, M3, and D3 using ultraviolet-visible spectroscopy. The complexation of succinoglycan and ferrous iron can cause structural changes, which were analyzed by circular dichroism spectroscopy. Furthermore, the complex could provide antioxidant activity through an anti-Fenton reaction. These results demonstrate that the low-molecular weight succinoglycans can effectively modulate iron biochemistry as a novel ferrous iron-acquisition system of S. meliloti. [ABSTRACT FROM AUTHOR]

The article discusses a study which demonstrated that increased exopolysaccharide succinoglycan production is not detrimental to symbiotic development but enhances the symbiotic productivity of Sinorhizobium meliloti 1021 with the host plant Medicago truncatula cv. ]emalong A17. The study showed that increased succinoglycan production was engineered by overexpression of the exoYgene. It also proposed several possible roles for succinoglycan in infection thread initiation and development.

Abstract: The isolated succinoglycan octasaccharide dimers isolated from Sinorhizobium meliloti 1021 have unique acyclic structures, displaying amphipathic properties against water. Thus, their potential usage as solubilizers of various water-insoluble drugs through non-covalent complexation are possible. In this study, we examined the solubility of a poorly water-soluble drug, haloperidol, in the presence of the acyclic form of succinoglycan dimers, and demonstrated that its solubility was increased up to 87 fold, Interestingly, the level of its solubility was even 7–10 fold higher than that achieved with β cyclodextrin or its derivatives that are cyclic forms, which is possibly due to the molecular flexibility of the acyclic structure of the dimers as well as the hydrophobic nature. Analyses of the stoichiometry and the stability constants for each complex were performed using phase solubility method, respectively. Additional analyses were also performed to confirm the formation of succinoglycan–drug complexes. Furthermore hypothetical 3-dimesional conformation of the complex was estimated through molecular docking simulations. Upon cytotoxicity test with a human cell line, the succinoglycan dimers displayed little effect up to 1000μM, suggesting their potential usage to improve solubility and bioavailability of poorly soluble therapeutic agents. [Copyright &y& Elsevier]

Th is paper evaluates the competitive ability of Rhizobium leguminosarum bv trifolii strain T49B1 used as inoculant for Trifolium repens L. (Viola) and indigenous population of rhizobia from chernozem, stagnosol and humic gleysol. Nodule bacteria were identified using calcofluor eff ects (CF) based on succinoglycan production, and confirmed by IAR patterns and RAPD fi ngerprinting (using SPH1 primer). T49B1 nodules occupancy level from 71.78% in pseudoglay to 89.56% in chernozem was detected. Inoculation by T49B1 strain showed it to be a very good competitor with the possibility to establish eff ective symbiosis and increase protein content compared to noninoculated (control) plants. [ABSTRACT FROM AUTHOR]

Swarming is a mode of translocation dependent on flagellar activity that allows bacteria to move rapidly across surfaces. In several bacteria, swarming is a phenotype regulated by quorum sensing. It has been reported that the swarming ability of the soil bacterium Sinorhizobium meliloti Rm2011 requires a functional ExpR/Sin quorum-sensing system. However, our previous published results demonstrate that strains Rm 1021 and Rm2011, both known to have a disrupted copy of expR, are able to swarm on semisolid minimal medium. In order to clarify these contradictory results, the role played by the LuxR-type regulator ExpR has been reexamined. Results obtained in this work revealed that S. meliloti can move over semisolid surfaces using at least two different types of motility. One type is flagellum-independent surface spreading or sliding, which is positively influenced by a functional expR gene mainly through the production of exopolysaccharide II (EPS II). To a lesser extent, EPS II-deficient strains can also slide on surfaces by a mechanism that is at least dependent on the siderophore rhizobactin 1021. The second type of surface translocation shown by S. meliloti is swarming, which is greatly dependent on flagella and rhizobactin 1021 but does not require ExpR. We have extended our study to demonstrate that the production of normal amounts of succinoglycan (EPS I) does not play a relevant role in surface translocation but that its overproduction facilitates both swarming and sliding motilities. [ABSTRACT FROM AUTHOR]

Propionibacterium freudenreichii is a bacterial species found in Swiss-type cheeses and is also considered for its health properties. The main claimed effect is the bifidogenic property. Some strains were shown recently to display other interesting probiotic potentialities such as anti-inflammatory properties. About 30% of strains were shown to produce a surface exopolysaccharide (EPS) composed of (1→3,1→2)-β-d-glucan due to a single gene named gtfF. We hypothesized that functional properties of P. freudenreichii strains, including their anti-inflammatory properties, could be linked to the presence of β-glucan. To evaluate this hypothesis, gtfF genes of three β-glucan-producing strains were disrupted. These knockout (KO) mutants were complemented with a plasmid harboring gtfF (KO-C mutants). The absence of β-glucan in KO mutants was verified by immunological detection and transmission electron microscopy. We observed by atomic force microscopy that the absence of β-glucan in the KO mutant dramatically changed the cell's topography. The capacity to adhere to polystyrene surface was increased for the KO mutants compared to wild-type (WT) strains. Anti-inflammatory properties of WT strains and mutants were analyzed by stimulation of human peripheral blood mononuclear cells (PBMCs). A significant increase of the anti-inflammatory interleukin-10 cytokine production by PBMCs was measured in the KO mutants compared to WT strains. For one strain, the role of β-glucan in mice gut persistence was assessed, and no significant difference was observed between the WT strain and its KO mutant. Thus, β-glucan appears to partly hide the anti-inflammatory properties of P. freudenreichii; which is an important result for the selection of probiotic strains [ABSTRACT FROM AUTHOR]

This study examines and compares the structural and rheological properties of succinoglycan exopolysaccharide made by fermentation of sucrose or date syrup at identical temperature, pH, and total soluble solid. Using thin-layer chromatography (TLC), Fourier transform infrared (FTIR) spectroscopy, and rotational viscometery structural and rheological properties of prepared exopolysaccharides were assessed. The variables under studies were biogum concentrations (0.5%, 1.0%, 1.5%, and 2.0% w/ w), temperature (5, 25 and 40°C), and pH (2.5, 4.0, 7.0, and 10.0). Results revealed that the quantity of exopolysaccharide produced in the date syrup (DSE) medium was three to five times greater than that of sucrose (SE) medium. The biogums exhibited non-Newtonian, shear-thinning behavior, and the viscosity of DSE was higher than SE at all tested concentrations. The TLC and FTIR spectroscopy assessments designated that the biogum is composed of glucose and galactose units, carrying a carboxylic group and indicated the presence of succinoglycan. The outcomes of this study could be useful to food industries seeking low cost biogum. [ABSTRACT FROM AUTHOR]

Abstract: Low-molecular-weight (LMW) succinoglycans (monomers, dimers, and trimers) were isolated from Sinorhizobium meliloti 1021 and have been firstly investigated by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) using 2,4,6-trihydroxyacetophenone (THAP) as an optimal matrix in the negative ion mode. The main fractions of LMW succinoglycans contain molecules assembled of octasaccharide subunits. MALDI-TOF mass spectra of the LMW succinoglycan monomers, the dimers, and the trimers showed the daughter ions resulting from the losses of the terminal galactose residues at the reducing ends, clearly indicating that the galactosyl linkages are more labile than the other glucosyl linkages. Furthermore, the losses of the acetyl groups as substituents rather than the succinyl and pyruvyl ester linkages by prompt fragmentation primarily occurred during MALDI-TOF analysis, suggesting the greater instability of acetyl linkages compared to pyruvyl and succinyl linkages. [Copyright &y& Elsevier]

In Sinorhizobium meliloti, the production of exopolysaccharides such as succinoglycan and exopolysaccharide II (EPS II) enables the bacterium to invade root nodules on Medicago sativa and establish a nitrogen-fixing symbiosis. While extensive research has focused on succinoglycan, less is known concerning the regulation of EPS II or the mechanism by which it mediates entrance into the host plant. Previously, we reported that the ExpR/Sin quorum-sensing system is required to produce the symbiotically active low-molecular-weight fraction of this exopolysaccharide. Here, we show that this system induces EPS II production by increasing expression of the expG-expC operon, encoding both a transcriptional regulator (ExpG) and a glycosyl transferase (ExpC). ExpG derepresses EPS II production at the transcriptional level from MucR, a RosR homolog, while concurrently elevating expression of expC, resulting in the synthesis of the low-molecular-weight form. While the ExpR/Sin system abolishes the role of MucR on EPS II production, it preserves a multitude of other quorum-sensing-independent regulatory functions which promote the establishment of symbiosis. In planktonic 5. meliloti, MucR properly coordinates a diverse set of bacterial behaviors by repressing a variety of genes intended for expression during symbiosis and enhancing the bacterial ability to induce root nodule formation. Quorum sensing precisely modulates the functions of MucR to take advantage of both the production of symbiotically active EPS II as well as the proper coordination of bacterial behavior required to promote symbiosis. [ABSTRACT FROM AUTHOR]

The article focuses on a research study related to anti-biofilm activity of an exopolysaccharide from a sponge-associated strain of Bacillus licheniformis. During the course of the study, polysaccharide was extracted from a Bacillus licheniformis strain associated with the marine organism Spongia officinalis. The polysaccharide isolated from sponge-associated B. licheniformis has several features that provide a tool for better exploration of novel anti-biofilm compounds.

Sinorhizobium meliloti is a soil bacterium that elicits the formation of root organs called nodules on its host plant, Medicago sativa. Inside these structures, the bacteria are able to convert atmospheric nitrogen into ammonia, which is then used by the plant as a nitrogen source. The synthesis by S. meliloti of at least one exopolysaccharide, succinoglycan or EPS II, is essential for a successful symbiosis. While exopolysaccharide-deficient mutants induce the formation of nodules, they fail to invade them, and as a result, no nitrogen fixation occurs. Interestingly, the low-molecular-weight fractions of these exopolysaccharides are the symbiotically active forms, and it has been suggested that they act as signals to the host plant to initiate infection thread formation. In this work, we explored the role of these rhizobial exopolysaccharides in biofilm formation and their importance in the symbiotic relationship with the host. We showed that the ExpR/Sin quorum-sensing system controls biofilm formation in S. meliloti through the production of EPS II, which provides the matrix for the development of structured and highly organized biofilms. Moreover, the presence of the low-molecular-weight fraction of EPS II is vital for biofilm formation, both in vitro and in vivo. This is the first report where the symbiotically active fraction of EPS II is shown to be a critical factor for biofilm formation and root colonization. Thus, the ability of S. meliloti to properly attach to root surfaces and form biofilms conferred by the synthesis of exopolysaccharides may embody the main function of these symbiotically essential molecules. [ABSTRACT FROM AUTHOR]

Exopolysaccharides, either succinoglycan or galactoglucan, are essential for the establishment of the symbiosis between Sinorhizobium meliloti and Medicago sativa (alfalfa). The ExoS/ChvI two-component regulatory system is known as a regulator of succinoglycan production but the genes that are directly regulated by ChvI have not been determined. Difficulty isolating exoS and chvI null mutants has prompted the suggestion that these genes are essential for S. meliloti viability. We have successfully isolated exoS and chvI null mutants using a merodiploid-facilitated strategy. We present evidence that the S. meliloti ExoS/ChvI two-component regulatory system is essential for symbiosis with alfalfa. Phenotypic analyses of exoS and chvI null mutant strains demonstrate that ExoS/ChvI controls both succinoglycan and galactoglucan production and is required for growth on over 21 different carbon sources. These new findings suggest that the ExoS/ChvI regulatory targets might not be the exo genes that are specific for succinoglycan biosynthesis but rather genes that have common influence on both succinoglycan and galactoglucan production. Other studied alpha-proteobacteria ExoS/ChvI orthologues are required for the bacteria to invade or persist in host cells and thus we present more evidence that this two-component regulatory system is essential for alpha-proteobacterial host interaction. [ABSTRACT FROM AUTHOR]

Abstract: Succinoglycan, a sinorhizobial exopolysaccharide produced by Sinorhizobium meliloti, is composed of an octasaccharide subunit. S. meliloti produces both high-molecular-weight and low-molecular-weight (M r <10,000) succinoglycans which consist of monomers, dimers, or trimers. Succinoglycan monomers were isolated and further purified in the monomer series (M1, M2, and M3) by the degree of succinylation. We used sinorhizobial octasaccharides (M1, M2, and M3) as chiral additives in capillary electrophoresis (CE) for chiral separation of catechin and also as chiral shift reagents with 13C NMR spectroscopy for chiral discrimination of catechin. Chiral separation of catechin took place when sinorhizobial octasaccharides (M2 and M3) were added to the background electrolyte (BGE) in CE. NMR signal splittings were also observed in the interactions of sinorhizobial octasaccharides with the enantiomers of catechin. Both chiral separation and discrimination of catechin depend on the presence of succinate substituents of the linear monomeric octasaccharide in CE and NMR spectroscopy, suggesting that succinylation of sinorhizobial octasaccharide is decisive for the effective chiral separation and discrimination of catechin. [Copyright &y& Elsevier]

The Sinorhizobium meliloti ExoS/ChvI two-component signaling pathway is required for the development of a nitrogen-fixing symbiosis between S. meliloti and its plant hosts. ExoS/ChvI also has important roles in regulating succinoglycan production, biofilm formation, motility, nutrient utilization, and the viability of free-living bacteria. Previous microarray experiments with an exoS96::Tn5 mutant indicated that ExoS/ChvI influences the expression of a few hundred genes, complicating the investigation of which downstream genes respond directly or indirectly to ExoS/ChvI regulation. To focus our study of ExoS/ChvI transcriptional target genes, we performed transcriptional profiling with chvI gain-of-function and reduced-function strains. The chvI gain-of-function strain that we used contains a dominant gain-of-function chvI allele in addition to wild-type chvI. We identified genes that, relative to their expression level in the wild type, are both upregulated in the chvI gain-of-function strain and downregulated in the reduced-function strain or vice versa. Guided by this focused set of genes, we performed gel mobility shift assays and demonstrated that ChvI directly binds the intergenic regions upstream of ropB1, SMb21440, and SMc01580. Furthermore, DNase I footprint analysis of the region upstream of SMc01580 identified a specific DNA sequence bound by ChvI and allowed the discovery of a possible motif for ChvI binding. Our results provide insight into the mechanism of how ExoS/ChvI regulates its downstream targets and lay a foundation for studying this conserved pathway with critical roles in free-living and symbiotic bacteria. [ABSTRACT FROM AUTHOR]