Effect of Ribocitrin on Glucan Synthesizing Enzymes of Streptococcus mutans E49

Enzymes participating in glucan synthesis by Streptococcus mutans E49 were separated into two fractions with distinctly different activities by chromatography on DEAE Bio-Gel A. The insoluble glucan (IG) was revealed to be formed by the coupling reaction of these two enzymes, dextransucrase (SGE), which synthesizes soluble glucan from sucrose, and a glucan insolubilizing enzyme (IGE), which forms IG from soluble glucan.

Ribocitrin was found to inhibit IG synthesis by inhibiting SGE.     

The Role of Zinc Atoms in Nuclease P1

A dextransucrase inhibitor, ribocitrin, was purified about 580-fold from a culture broth of Streptomyces neyagawaensis MF980-CF1 by combination chromatography.

Ribocitrin is a previously unknown type of oligosaccharide composed of ribose. It inhibited the crude preparation of dextransucrase noncompetitively with regard to sucrose and the inhibitory activity (Inh%) was sensitive to pH. It was very stable at alkaline pH values, but gradually lost its inhibitory activity as the acidity increased. It had no antimicrobial activity. It did not inhibit glycoside hydrolases and was not susceptible to the above enzymes. It had a low toxicity.

Plaque formation of Streptococcus mutans E49 on a smooth glass surface was diminished by ribocitrin and the colony form of this microorganism on Mitis Salivarius agar was evidently affected by ribocitrin.     

Construction of Chimeric Glucansucrases for Analyzing Substrate-binding Regions That Affect the Structure of Glucan Products

A gene that encodes dextransucrase S (dsrS) from Leuconostoc mesenteroides NRRL B-512F encodes a glucansucrase dextransucrase S (DSRS) which mainly produces water-soluble glucan (dextran), while the dsrT5 gene derived from dsrT of the B-512F strain encodes an enzyme dextransucrase T5 (DSRT5), which mainly produces water-insoluble glucan. Tyr340-Asn510 of DSRS and Tyr307-Asn477 of DSRT5 (Site 1), Lys696-Gly768 of DSRS and Lys668-Gly740 of DSRT5 (Site 2), and Asn917-Lys1131 of DSRS and Asn904-Lys1118 of DSRT5 (Site 3) were exchanged and six different chimeric enzymes were constructed. Water-soluble glucan produced by recombinant DSRS was composed of 64% 6-linked glucopyranoside (Glcp), 9% 3,6-linked Glcp, and 13% 4-linked Glcp. Water-insoluble glucan produced by recombinant DSRT5 was composed of 47% 6-linked Glcp and 43% 3-linked Glcp. All of the chimeric enzymes produced glucans different from the ones produced by their parental enzymes. Some of the glucans produced by chimeric enzymes were extremely changed. The Site 1 chimeric enzyme of DSRS (STS1) produced water-soluble glucan composed mostly of 6-linked Glcp. That of DSRT5 (TST1) produced water-insoluble glucan composed mostly of 4-linked Glcp. The Site 3 chimeric enzyme of DSRS (STS3) produced mainly water-insoluble glucan, DSRT5 (TST3) produced mainly water-soluble glucans, and all of the glucan fractions consisted of 3-Glcp, 4-Glcp, and 6-Glcp. The amounts of the three linkages in the water-soluble glucan produced by TST3 were about 1:1:1. Site 1 was assumed to be important for making or avoiding making α-1,4 linkages, while Site 3 was assumed to be important for determining the kinds of glucosyl linkages made.     

Ultrastructure and Chemical Analysis of the Cell Wall of Pythium debaryanum1

The ultrastructure and component polysaccharides of the cell wall of Pythium debaryanum IFO-5919 were investigated. From results obtained by means of acid, alkali, Schweitzer reagent and β-1, 3-glucanase treatments and electron microscopy, it was concluded that 1) the acid-extracted fraction was a 1,3-linked branched glucan, 2) the alkali-extracted fraction was a mixture of 1,3-, 1,6-, and 1,3,6-linked highly branched two glucans, 3) the Schweitzer reagent-extracted fraction was a β-1, 4-linked glucan, 4) the cell wall was constructed from two types of cullulosic microfibrils, as a frame and as a finer network, and amorphous β-1, 3-glucan including β-1, 6-linkage, 5) cellulosic microfibrils were covered by matrix material consisting of a mixture of amorphous β-1, 3-linked and β-1, 6-linked branching glucans.     

Surface carbohydrates of Rhizobium I. β-1, 2-Glucans

Because of increased interest in surface carbohydrates of Rhizobium in relation to host specificity, phenol — water extractions were carried out of whole cells of Rhizobium strains of the species R. leguminosarum, R. phaseoli, R. trifolii and R. meliloti.Fractionation of the crude extracts with cetavlon afforded polysaccharide mixtures, which were essentially free of RNA and acidic exopolysaccharide (EPS). They could be separated into a high molecular weight heteropolysaccharide fraction of lipopolysaccharide (LPS) nature and a low molecular weight glucan fraction. Glucan turned out to be the principal polysaccharide component of the cells (up to 10% of the dry cell weight), when cultivated in carbohydrate-rich media, and to be present as firmly attached capsular material.Glucan (mol wt 3000) structure was elucidated by methylation and periodate oxidation techniques. Methylation yielded 3, 4, 6-tri-O-methyl-d-glucose, characterized by GLC-MS, as the only product of hydrolysis of the fully methylated glucan. The glucan consumed 1 mole of periodate per mole anhydroglucose unit and gave sophorose on partial hydrolysis. From these data a linear -1,2-linked glucan structure was deduced. The occurrence of -1,2-glucan and the implications for the specific binding properties of Rhizobium cells are discussed.     

Chitin and β(1–3) glucan synthases in the protoplastic entomophthorales

(1–3) glucan and chitin synthases were studied in spontaneously produced protoplasts and in the mycelium (hyphal body) of the entomopathogenic Entomophthorale species Entomophaga aulicae, Conidiobolus obscurus and Entomophthora muscae. The absence of wall in protoplasts was correlated to an absence of chitin synthase and to a very low (1–3) glucan synthase activity, whereas these two polysaccharide synthases were present and active in the walled hyphal bodies. Physicochemical properties of chitin and (1–3) glucan synthases such as localization, optimum pH and temperature, activation by disaccharides and proteases were similar to those found in other fungi unable to spontaneously produce protoplasts and could not be related to the ability for protoplastic Entomophthorale species to produce and proliferate under a protoplast form. The absence or the low chitin and glucan synthase activites in Entomophthorale protoplasts was not due to an absence of proteolytic activation of the enzyme. However, all protoplast fractions contained inhibitory substances of glucan and chitin synthase activities. These inhibitors were stable and specific of the protoplast stage. They were not glucanase nor chitinase. These results suggest that the absence of wall synthesis in Entomophthorale protoplasts is due to a continuous inhibition of (1–3) glucan and chitin synthase activities by intracellular compounds and also for glucan synthase by protoplast medium constituents such as NaCl and fetal calf serum.Abbreviations BSA bovine serum albumin - DFP diisopropylfluorophosphate - EDTA ethylenediamine tetraaoetic acid - FCS fetal calf serum - GlcNAc N-acetylglucosamine - TCA trichloroacetic acid - 2 k pellet 2,000 g wall fraction - 140 k pellet 140,000 g particulate fraction - 140 k supernatant 140,000 g soluble fraction     

Biochemical and Immunological Studies on Aspergillus

Two kinds of polysaccharides, glucan and glycopeptide (galactomannan-peptide), were obtained from Aspergillus fumigatus (IFO 5840) by extraction with 50% pyridine and were purified by fractional precipitation with acetone, by a column chromatography on Dowex-50 and DEAE-cellulose and by the gel filtration on Sephadex G-50 and G-200. The glycopeptide, designated APSK-66 fraction, showed both an Arthus and delayed type (tuberculin type) skin reactions in sensitized rabbits and guinea pigs. By treatment with proteolytic enzymes, the delayed type skin reactivity of APSK-66 fraction was reduced but the Arthus type skin reactivity was not affected. However, the Arthus type skin reactivity of APSK-66 fraction was completely lost by periodate oxidation, and the delayed type skin reactivity of APSK-66 fraction was retained. The APSK-66 fraction showed precipitation, complement fixation and passive hemagglutination reactions with rabbit antisera against A. fumigatus. Glucan, designated as APSK-33 fraction, did not show any immunological activity when tested in the present experiment. The chemical structures of the glucan and galactomannan were discussed.     

Study of supramolecular structures released from the cell wall of Candida albicans by ethylenediamine treatment

Candida albicans cell wall components were analyzed by ethylenediamine (EDA) treatment. Based on their different solubility properties, the cell wall components produced three fractions (A, B, and C). Fractions B (EDA-soluble, water-insoluble) and C (EDA-insoluble) contained glucan, chitin, and protein in different proportions. After zymolyase (mainly a β-glucanase complex) or chitinase treatment of fractions B and C, more polysaccharides and proteins were solubilized by a second EDA treatment, suggesting that the solubility of the polymers in EDA depends on the degree of polymer interactions. Western blot analysis using two monoclonal antibodies (1B12 and 4C12) revealed electrophoretic patterns that were similar in mycelial and yeast morphologies, except that in material obtained from mycelial walls, an additional band was detected with MAb 1B12. Fluorescence microscopy of cell wall fractions treated with FITC-labeled Con-A, Calcofluor white, and FITC-labeled agglutinin showed that glucan and mannoproteins are uniformly distributed in fractions B and C, while chitin is restricted to distinct patches. Transmission electron microscopy demonstrated that fraction C maintained the original shape of the cells, with an irregular thickness generally wider than the walls. When fraction C was treated with chitinase, the morphology was still present and was maintained by an external glucan layer, with an internal expanded fibrillar material covering the entire cellular lumen. Degradation of the glucan skeleton of fraction C with zymolyase resulted in the loss of the morphology. Received: 1 April 1996 / Accepted: 2 September 1996     

Purification and Properties of Lytic β-Glucanase from an Arthrobacter Bacterium

A glucanase was isolated from a culture fluid of an Arthrobacter bacterium. The purified enzyme preparations consisted of the glucanase components having the same enzymatic activity. The enzyme was stable in a broad pH range, but lost its activity rapidly at above 60°C. Optimum pH values were found to be 5.5~6.5.

The glucanase attacked the following glucan preparations and liberated a relatively small amount of reducing power: Saccharomyces cerevisiae glucan, Candida albicans glucan, Saccharomyces fragilis glucan, pachyman, curdlan and laminaran. The most prominent sugar spot on the chromatogram of the digest from yeast glucan was identified with laminan-pentaose, and the other faint spots with a series of laminaridextrins. The β-1,6 glucosidic bonds in yeast glucan were not hydrolyzed and concentrated in a soluble fraction which was found near the origin of the chromatogram.     

Interaction of the β-Transglycosylase of Trichoderma longibrachiatum with Cellulose

The effects of cellulose on the production and stimulation of β-transglycosylase were studied. The β-transglycosylase of Trichoderma longibrachiatum was produced specifically in the presence of cellulose in Czapeck-Dox medium containing sucrose as a sole carbon source. The enzyme activity was stimulated by the addition of cellulose in the reaction mixture, where the transfer reaction product (a water-insoluble glucan) was apparently synthesized on the surface of the added cellulose fibers.

The hyphal wall fraction of the fungus had the same stimulatory effect on β-transglycosylase as the cellulose fibers. A cellulose-like material in this fraction was found by partial acid hydrolysis and gas chromatography. Cellotriose was the smallest substrate effective for the synthesis of a water-insoluble glucan in the presence of cellulose by the β-transglycosylase, though a significant amount of glucan could not be synthesized without the addition of cellulose.     

Chloroplast and extrachloroplastic starch-degrading enzymes in Pisum sativum L.

The organelles of soybean (Glycine max (L.) Merr.) protoplasts were separated using a recently developed procedure which allows rapid (3-h) recovery of a fraction enriched for coated vesicles (CVs). As determined by marker-enzyme enrichment and ultrastructural analysis of isolated membrane fractions, endoplasmic reticulum, Golgi membranes, glucan-synthase-II (EC 2.4.1.34)-containing membranes (putative plasma membrane), mitochondria, and CVs were enriched in separate fractions in a sucrose density gradient. Glucan synthase I (EC 2.4.1.12) had the highest specific activity in the Golgi-enriched and CV-enriched fractions and was found to comigrate with CVs upon rate-zonal centrifugation of a CV-enriched fraction. For further elucidation of the role of these latter organelles in cell-wall regeneration, freshly isolated protoplasts were pulsed with [³H]glucose for 20 min, and the disappearance of label from the organelles was followed for the ensuing 1 h. Although a CV-enriched fraction contained glucan synthase I, it contained very small amounts of labelled polysaccharide during the period of study. Pulse-chase experiments with [³H]glucose helped to confirm the role of the Golgi apparatus in secretion of matrix polysaccharides by protoplasts.Abbreviations CV(s) coated vesicle(s) - Da dalton - ER endoplasmic reticulum - GSI,II glucan synthase I and II, respecitively Two whom correspondence should be directed. Address after February 1986:Department of Biology, Texas A&M University. College Station, TX 77843-3258, USA     

Isolation and characterization of α‐(1→3)‐glucan‐degrading bacteria from the gut of Diaperis boleti feeding on Laetiporus sulphureus

Bacteria degrading α‐(1→3)‐glucan were sought in the gut of fungivorous insects feeding on fruiting bodies of a polypore fungus Laetiporus sulphureus, which are rich in this polymer. One isolate, from Diaperis boleti, was selected in an enrichment culture in the glucan‐containing medium. The bacterium was identified as Paenibacillus sp. based on the results of the ribosomal DNA analysis. The Paenibacillus showed enzyme activity of 4.97 mU/cm³ and effectively degraded fungal α‐(1→3)‐glucan, releasing nigerooligosaccharides and a trace amount of glucose. This strain is the first reported α‐(1→3)‐glucan‐degrading microorganism in the gut microbiome of insects inhabiting fruiting bodies of polypore fungi.     

Crystalline Features of Streptococcal (l→3)-α-D-Glucans of Human Saliva

Crystalline polymorphs of the backbone (l→3)-α-D-glucans of two streptococcal α-glucans were studied by X-ray diffraction measurements in comparison with that of a fungal (l→3)-α-D-glucan. The glucan produced by S. salivarius changed its polymorph from the hydrated form at 100% relative humidity to the dehydrated form under vacuum, that produced by cariogenic S. mutans took the dehydrated form only, and the fungal glucan always showed the hydrated form. The difference of polymorphic behavior was ascribed to the molecular weight of the glucan since the fungal glucan showed the highest viscosity, the saliverius glucan, middle, and the mutans glucan, the lowest.     

Control of Bemisia tabaci by entomopathogenic fungi isolated from arid soils in Argentina

Entomopathogenic Hypocreales were isolated from arid soils in Argentina using Tenebrio molitor as bait and tested for their biological performance at 30°C and 45–65% RH. Conidial germination was tested in three vegetable oils (sunflower, olive and maize) at two concentrations (1% and 10%) to evaluate their compatibility for further liquid formulations. According to radial growth and germination results, we selected four isolates to test their pathogenicity against second instar B. tabaci nymphs with the selected oil formulations at 30°C. CEP381 and CEP401 showed the highest radial growth. Isolates CEP381, CEP401, CEP413 and CEP409 (Metarhizium spp.) had similar germination percentages as compared with water control when germinated on either sunflower, olive or maize oils at 10% v/v. The highest mortality of B. tabaci was observed for the isolates CEP381 in sunflower oil and CEP401 in olive oil. Molecular identification of isolates was performed using ITS4–5 primers. All isolates belong to the Metarhizium core group. Tested isolates could grow and infect B. tabaci nymphs at 30°C in some of the vegetable oils as carriers, providing new possibilities for integrated pest management of Bemisia tabaci.     

Metabolic engineering of indole glucosinolates in Chinese cabbage hairy roots expressing Arabidopsis CYP79B2, CYP79B3, and CYP83B1

Indole glucosinolates (IG), a group of secondary metabolites found almost extensively in the order Brassicales, play an important role in the interaction between plant and insect or microorganism. In order to explore the possibility of IG metabolic engineering in Chinese cabbage hairy roots, three Arabidopsis cDNAs CYP79B2, CYP79B3, and CYP83B1 combined with rolABC were introduced into Chinese cabbage by Agrobacterium-mediated transformation. Overexpression of CYP79B2, CYP79B3, or CYP83B1 alone did not affect the accumulation levels of IG in transgenic hairy roots. However, when CYP83B1 was overexpressed together with CYP79B2 and/or CYP79B3, some of the transgenic hairy roots accumulated higher levels of glucobrassicin (GBC) or 4-methoxy glucobrassicin (4-OMeGBC) than control hairy root line carrying rolABC vector. With regard to the IG accumulation, overexpression of all three cDNAs showed no better than overexpression of both cDNAs. Both 4-OMeGBC and neoglucobrassicin (neo-GBC) were found to be the main components of IG that comprise about 90% of total IG in all types of Chinese cabbage hairy root lines. In transgenic hairy root lines rB3B1-8 and rB2B1B3-5, 4-OMeGBC increased to 2 and 1.5-fold, while neo-GBC decreased to 0.5 and 0.6-fold, respectively. This suggests that an increased production of 4-OMeGBC causes a reduction of neo-GBC level since the two types derive from a common precursor GBC. However, in terms of the total IG level, the transgenic hairy roots did not show significant differences from controls.     

Molecular identification of the economically important freshwater mussels (Mollusca–Bivalvia–Unionoida) of Thailand: developing species‐specific markers from AFLPs

Shells of certain freshwater mussel (Unionoida) species are highly demanded and serve as raw material for a range of decorative and pharmaceutical products. In Thailand, most animals for this purpose are currently harvested from wild populations, with unionoid culture still being in its infancy. Whilst reliable species identification is a prerequisite for developing a large‐scale industry, identification by morphological means is hampered by extensive phenotypic plasticity and poor knowledge of species delimitations. To facilitate alternative molecular identification, we developed species‐specific markers for the three Thai unionoids with considerable economic potential (CEP): that is, Chamberlainia hainesiana, Hyriopsis desowitzi and Hyriopsis myersiana. For this purpose, amplified fragment length polymorphism (AFLP) fingerprints using 24 specific primer pairs were generated for eight samples of each CEP species and four samples of the closely related, non‐CEP species Contradens contradens. Cloning and sequencing of 13 CEP species‐specific AFLP bands revealed fragment collision at three occasions. In total, 16 species‐specific primer pairs were designed and tested on 92 Thai specimens spanning seven species and four genera. Thereby, specificity of (1) three primers to C. hainesiana, (2) one primer to H. desowitzi + Hyriopsis bialata, (3) one primer to H. myersiana + H. bialata and (4) four primers to all three Hyriopsis species tested was confirmed. Respective multiplex PCR protocols are provided. The developed primers enable cheap, quick and reliable identification of the Thai CEP species by one to three PCRs and offer a tool for a range of additional applications within mussel culture and ecological and evolutionary research on these important organisms.