Isolation and characterization of exocellular polysaccharides produced by Bifidobacterium longum

When grown anaerobically at pH values above 5.0, on ultrafiltered complex media containing excess lactose, Bifidobacterium longum formed up to 140 mg 1^–1 (glucose equiv.) exopolysaccharides. The highest yield was obtained when the cells were cultivated in a peptone/yeast extract medium with pH controlled by additions of NH₄OH. Whatever the conditions under study, exopolysaccharides represented about 30% of the polysaccharides produced by B. longum after 48 h of culture. Crude pronase-treated exopolysaccharide preparations were adsorbed on ion-exchange chromatographic resin to yield an anionic heteropolysaccharide fraction. Two subfractions with apparent molecular masses of 1.2 MDa and 0.36 MDa respectively were subsequently recovered after gel filtration on Sepharose 4B. In both subfractions, glucose, galactose and small amounts of uronic acids and hexosamines were present in similar molar proportions, suggesting that the excreted polymers may be synthesized from the same base unit and may have a structure resulting from repeating subunits.     

Immunological differentiation of Penicillium species

Antisera were obtained from a rabbit immunized with Penicillium verrucosum var. verrucosum. These antisera were characterized by immunofluorescence and by indirect enzyme-linked immunosorbent assay for their reactivity with 44 strains of moulds. Antigenically, P. verrucosum var. verrucosum (subgenus Penicillium) appears to be similar to strains belonging to subgenus Furcatum, but strongly different from Penicillium frequentans (subgenus Aspergilloides). Specific absorption of antibodies to antigens confirmed the existence of similar biochemical structures on Penicillium frequentans, Aspergillus versicolor, and Aspergillus fumigatus. Immunological procedures may thus significantly contribute to refine the taxonomic classification of moulds.     

Structural characterization of the exocellular polysaccharides produced by Streptococcus thermophilus SFi39 and SFi12.

We investigated the structures of the exopolysaccharides (EPSs) produced by Streptococcus thermophilus SFi39 and SFi12. Both polymers were found to have molecular masses of greater than 2 x 10(6) Da. The SFi39 EPS consisted of D-glucose and D-galactose in a molar ratio of 1:1, whereas the SFi12 EPS was composed of D-galactose, L-rhamnose, and D-glucose in a molar ratio of 3:2:1. Methylation analysis of and nuclear magnetic resonance spectra recorded from the native polysaccharide, as well as oligosaccharides released by partial acid hydrolysis, allowed the complete structural determination of the SFi39 EPS, which consists of the following tetrasaccharide repeating unit: [formula: see text] Similar spectra recorded only from the native polysaccharide were sufficient to allow the structural determination of the SFi12 EPS, which consists of the following hexasaccharide repeating unit: [formula: see text] This study shows that the texturizing properties of different S. thermophilus ropy strains are based on the production of EPSs exhibiting chemical similarities but structural differences.     

Low molecular weight metabolites produced by various Penicillium species

Low-molecular weight volatile metabolites produced by Penicillium farinosum, P. citrinum, P. camemberti and P. chrysogenum were investigated. During first 40 days of cultivation the fungi produced mainly C-8 compounds, and later mainly 2-hexenal was synthesized. Addition of 0.1% linoleic acid significantly stimulated the secretion of volatile metabolites. P. citrinum and P. farenosum produced large quantities of geosmin.     

Immunological relationship of extra-cellular polysaccharide antigens produced by different mould species

Moulds are able to produce extracellular polysaccharide antigens which are heat-stable and almost genus specific. Of 44 different strains of Penicillium 41 (93%) and all 12 strains of Aspergillus tested produced detectable quantities of an immunologically related antigen. Additionally 10 of these 56 strains produced an antigen immunologically related to the antigen produced by the genera Mucor and Fusarium. Immunologically different, but genus-specific antigens were produced by each of the species belonging to the genus Geotrichum, Fusarium, Cladosporium, Mucor and Rhizopus. The antigens produced by Mucor and Rhizopus, however, were immunologically related.     

Characteristics and role of the exocellular polysaccharides produced by five cyanobacteria isolated from phototrophic biofilms growing on stone monuments

Three coccoid and two filamentous cyanobacterial strains were isolated from phototrophic biofilms exposed to intense solar radiation on lithic surfaces of the Parasurameswar Temple and Khandagiri caves, located in Orissa State, India. Based on to their morphological features, the three coccoid strains were assigned to the genera Gloeocapsosis and Gloeocapsa, while the two filamentous strains were assigned to the genera Leptolyngbya and Plectonema. Eleven to 12 neutral and acidic sugars were detected in the slime secreted by the five strains. The secretions showed a high affinity for bivalent metal cations, suggesting their ability to actively contribute to weakening the mineral substrata. The secretion of protective pigments in the polysaccharide layers, namely mycosporine amino acid-like substances (MAAs) and scytonemins, under exposure to UV radiation showed how the acclimation response contributes to the persistence of cyanobacteria on exposed lithoid surfaces in tropical areas.     

Characteristics and role of the exocellular polysaccharides produced by five cyanobacteria isolated from phototrophic biofilms growing on stone monuments

Three coccoid and two filamentous cyanobacterial strains were isolated from phototrophic biofilms exposed to intense solar radiation on lithic surfaces of the Parasurameswar Temple and Khandagiri caves, located in Orissa State, India. Based on to their morphological features, the three coccoid strains were assigned to the genera Gloeocapsosis and Gloeocapsa, while the two filamentous strains were assigned to the genera Leptolyngbya and Plectonema. Eleven to 12 neutral and acidic sugars were detected in the slime secreted by the five strains. The secretions showed a high affinity for bivalent metal cations, suggesting their ability to actively contribute to weakening the mineral substrata. The secretion of protective pigments in the polysaccharide layers, namely mycosporine amino acid-like substances (MAAs) and scytonemins, under exposure to UV radiation showed how the acclimation response contributes to the persistence of cyanobacteria on exposed lithoid surfaces in tropical areas.     

Structure of an exocellular polysaccharide produced by Streptococcus thermophilus

Streptococcus thermophilus strains grown on skimmed milk produced a viscosifying, exocellular, and water-soluble polysaccharide which contains D-glucose, D-galactose, and N-acetyl-D-galactosamine in the ratio of 1:2:1. Methylation analysis identified the glycosidic linkages in the tetrasaccharidic repeating-unit, and Smith degradation and nitrous deamination after N-deacetylation gave the sequence of monosaccharides in the repeating-unit. The anomeric configurations of the sugar residues were determined by oxidation of the peracetylated polysaccharide with chromium trioxide and by 1H- and 13C-n.m.r. spectroscopy. The following structure was assigned to the repeating unit of the polysaccharide,----3)-beta-D-Galp-(1----3)-[alpha-D-Galp-(1----6)]-beta- D- Glcp-(1----3)-alpha-D-GalpNAc-(1----.     

Structure of the exocellular D-glucan produced by Neisseria polysaccharea

Neisseria polysaccharea (LNP 462, NCTC 11858), proposed as a prototype strain constituting a new taxon in the genus Neisseria, produces copious amounts of polysaccharide when grown on agar containing 1-5% sucrose. Plate-grown cells produced an exocellular polysaccharide which was composed of D-glucose, had [alpha]D +222 degrees (water), and was shown from composition, specific optical rotation, methylation, enzymic hydrolysis, and 13C nuclear magnetic resonance studies to have an amylopectinlike structure containing mainly 1,4-linked alpha-D-glucopyranosyl residues, but also containing ca. 6% 4,6-di-O-substituted alpha-D-glucopyranosyl branch points.     

Hydrolysis of the polysaccharides of straw by enzymes produced by a mutant strain of the fungus Penicillium pinophilum

The saccharification of the polysaccharides of barley, oat, and wheat straws and Solka Floc was studied using the extracellular enzyme system synthesized by mutant strain NTG III/6 of the fungus Penicillium pinophilum 87160iii. The enzymes obtained in cultures containing Solka Floc or barley straw as the carbon source were compared. Solka Floc at 10% (w/v) concentration was hydrolyzed to the extent of 70% in 72 h at 50 degrees C using a reaction mixture containing 7 filter paper units/mL of cellulase induced on Solka Floc, but hydrolysis was increased to 90% when the enzyme induced on barley straw was used. Under the same conditions, the polysaccharides in barley, oat, and wheat straws were hydrolyzed, respectively, in 72 h, to the extent of 42-48%, 62%, and 52%, but hydrolysis was increased to 93%, 100%, and 92%, respectively, after treatment of the substrates with alkaline-H(2)O(2) reagent at room temperature.     

The structure of the exocellular polysaccharide produced by Rhodococcus sp. RHA1

Rhodococcus sp. RHA1 is a Gram-positive actinomycete capable of metabolizing a wide spectrum of organic compounds whose survival in chemically hostile environments is believed to be in part due to the production of an exocellular polysaccharide (EPS). In order to investigate the functional nature of the EPS, its structure was determined using a combinatory approach including hydrolysis, composition, and methylation, analysis methods, as well as 2D (1)H and (13)C NMR spectroscopy. The EPS was found to be a high-molecular-mass polymer of a repeating tetrasaccharide unit composed of D-glucuronic acid, D-glucose, D-galactose, L-fucose and O-acetyl (1:1:1:1:1), and has the structure:     

Exocellular polysaccharides produced by lactic acid bacteria.

The production of homopolysaccharides (dextrans, mutans) and heteropolysaccharides by lactic acid bacteria, their chemical composition, their structure and their synthesis are outlined. Mutans streptococci, which include Streptococcus mutans and S. sobrinus produce soluble and insoluble alpha-glucans. The latter may contain as much as 90% alpha-1-3 linkages and possess a marked ability to promote adherence to the smooth tooth surface causing dental plaque. Dextrans produced by Leuconostoc mesenteroides are high molecular weight alpha-glucans having 1-6, 1-4 and 1-3 linkages, varying from slightly to highly branched; 1-6 linkages are predominant. Emphasis is put on exopolysaccharide producing thermophilic and mesophilic lactic acid bacteria, which are important in the dairy industry. The produced polymers play a key role in the rheological behaviour and the texture of fermented milks. One of the main problems in this field is the transitory nature of the thickening trait. This instability is not yet completely understood. Controversial results exist on the sugar composition of the slime produced, but galactose and glucose have always been identified with galactose predominating in most cases.     

大豆连作障碍研究Ⅰ．大豆连作土壤紫青霉菌的毒素作用研究

研究分析了大豆连作、轮作土壤微生物区系,发现连作大豆根际土壤真菌富集,以其优势真菌回接大豆．紫青霉菌（Ｐｅｎｉｃｉｌｌｉｕｍｐｕｒｐｕｒｏｇｅｎｕｍ）能强烈抑制大豆生长发育．在实验室条件下分离获得该菌产生的毒素粗结晶,５μｇ·ｍｌ－１水培液中即可观察到大豆根系受害,根毛很少生长;３０μｇ·ｍｌ－１水培液中大豆主根褐变严重,侧根几乎不再生长;２００μｇ·ｍｌ－１导致一些大豆品种幼苗在２周内死亡这些结果表明,连作大豆土壤中该菌的大量存在及其产生的毒素是大豆连作障碍产生的主要因素．     

Calcofluor- and lectin-binding exocellular polysaccharides of Azospirillum brasilense and Azospirillum lipoferum.

Extracellular polysaccharides synthesized by Azospirillum brasilense and A. lipoferum were shown on agar plates and liquid flocculating cultures. The six strains used in this work expressed a mucoid phenotype, yielding positive calcofluor fluorescence under UV light. The calcofluor-binding polysaccharides were distributed between the capsular and exopolysaccharide fractions, suggesting exocellular localization. No calcofluor fluorescence was observed in residual cells after separation of the capsular and exopolysaccharide fractions. Cellulose content was significantly higher in flocculating than in nonflocculating cultures. Failure to induce flocculation by addition of cellulose (100 mg/ml) to nonflocculating cultures, together with the sensitivity of flocs to cellulase digestion, suggested that cellulose is involved in maintenance of floc stability. Different A. brasilense and A. lipoferum strains bound to a wheat lectin (fluorescein isothiocyanate-wheat germ agglutinin), indicating the occurrence of specific sugar-bearing receptors for wheat germ agglutinin on the cell surface. The biochemical specificity of the reaction was shown by hapten inhibition with N-acetyl-D-glucosamine. All six strains failed to recognize fluorescein isothiocyanate-soybean seed lectin under our experimental conditions. We conclude that azospirilla produce exocellular polysaccharides with calcofluor- and lectin-binding properties.