Dextranase Production Using Marine Microbacterium sp. XD05 and Its Application

Dextranase, also known as glucanase, is a hydrolase enzyme that cleaves α-1,6 glycosidic bonds. In this study, a dextranase-producing strain was isolated from water samples of the Qingdao Sea and identified as Microbacterium sp. This strain was further evaluated for growth conditions, enzyme-producing conditions, enzymatic properties, and hydrolysates. Yeast extract and sodium chloride were found to be the most suitable carbon and nitrogen sources for strain growth, while sucrose and ammonium sodium were found to be suitable carbon and nitrogen sources for fermentation. The optimal pH was 7.5, with a culture temperature of 40 °C and a culture time of 48 h. Dextranase produced by strain XD05 showed good thermal stability at 40 °C by retaining more than 70% relative enzyme activity. The pH stability of the enzyme was better under a weak alkaline condition (pH 6.0-8.0). The addition of NH4+ increased dextranase activity, while Co2+ and Mn2+ had slight inhibitory effects on dextranase activity. In addition, high-performance liquid chromatography showed that dextran is mainly hydrolyzed to maltoheptanose, maltohexanose, maltopentose, and maltootriose. Moreover, it can form corn porous starch. Dextranase can be used in various fields, such as food, medicine, chemical industry, cosmetics, and agriculture.

Effects of an enzyme agent containing mutanase and dextranase for treatment of biofilms in bacteria- and yeast-infected canine otitis externa

The purpose of this study was to evaluate in detail both the in vivo and in vitro efficacy of the enzyme agents, ZYMOX® Plus Otic (ZYMOX-P), in the treatment of canine otitis externa (OE). Eight dogs with a diagnosis of non-seasonal severe chronic OE were recruited for the study. ZYMOX-P was administered for 2-4 weeks. The Otitis Index Score (OTIS3) and bacteria or yeast colony growth were measured. Also, minimum biofilm (BF) formation inhibition concentration (MBIC) and BF bactericidal concentration (BBC) were measured in vitro. OTIS3 showed a statistically significant reduction after treatment (88.2%, p⟨0.001; pre-treatment = 11.0 ± 0.9; post-treatment = 1.3 ± 0.4, mean ± SEM). The individual OTIS scores, erythema, edema, erosions/ ulcerations, exudate and pruritus showed significant reduction (85.7%, 95.7%, 83.3%, 80.0%, and 89.3%, respectively). Microscopic examination revealed the presence of BF exopolysaccharide in all 8 ear samples when stained with alcian blue. Seven of the 8 dogs (87.5%) showed a reduction in colony growth. ZYMOX-P was effective at 34-fold and 16-fold dilutions on MBIC and BBC, respectively. These findings indicate that ZYMOX-P has efficacy against BF-related infection and is beneficial when used for the management of canine OE.

Effects of hulless barley and exogenous beta-glucanase levels on ileal digesta soluble beta-glucan molecular weight, digestive tract characteristics, and performance of broiler chickens

The reduced use of antibiotics in poultry feed has led to the investigation of alternatives to antibiotics, and one such substitution is fermentable carbohydrates. Exogenous β-glucanase (BGase) is commonly used in poultry fed barley-based diets to reduce digesta viscosity. The effects of hulless barley (HB) and BGase levels on ileal digesta soluble β-glucan molecular weight, digestive tract characteristics, and performance of broiler chickens were determined. A total of 360 day-old broilers were housed in battery cages (4 birds per cage) and fed graded levels of high β-glucan HB (CDC Fibar; 0, 30, and 60% replacing wheat) and BGase (Econase GT 200 P; 0, 0.01, and 0.1%) in a 3 × 3 factorial arrangement. Beta-glucan peak molecular weight in the ileal digesta was lower with 30 and 60 than 0% HB, whereas the peak decreased with increasing BGase. The weight average molecular weight was lower at 0.1 than 0% BGase in wheat diets, whereas in HB diets, it was lower at 0.01 and 0.1 than 0% BGase. The maximum molecular weight was lower with 0.01 and 0.1 than 0% BGase regardless of the HB level. The maximum molecular weight was lower with HB than wheat at 0 or 0.01% BGase. Overall, empty weights and lengths of digestive tract sections increased with increasing HB, but there was no BGase effect. Hulless barley decreased the duodenum and jejunum contents, whereas increasing the gizzard (diets with BGase), ileum, and colon contents. The jejunum and small intestine contents decreased with increasing BGase. Ileal and colon pH increased with increasing HB, but there was no BGase effect. Treatment effects were minor on short-chain fatty acids levels and performance. In conclusion, exogenous BGase depolymerized the ileal digesta soluble β-glucan in broiler chickens in a dose-dependent manner. Overall, feed efficiency was impaired by increasing HB levels. However, HB and BGase did not affect carbohydrate fermentation in the ileum and ceca, although BGase decreased ileal viscosity and improved feed efficiency at the 0.1% dietary level.

Optimization of Fungal Dextranase Production and Its Antibiofilm Activity, Encapsulation and Stability in Toothpaste

Dextranase catalyzes the degradation of the substrate dextran, which is a component of plaque biofilm. This enzyme is involved in antiplaque accumulation, which can prevent dental caries. The activity of crude dextranase from Penicillium roquefortii TISTR 3511 was assessed, and the maximum value (7.61 unit/g) was obtained at 37 °C and pH 6. The Plackett–Burman design was used to obtain significant factors for enhancing fungal dextranase production, and three influencing factors were found: Dextran, yeast extract concentration and inoculum age. Subsequently, the significant factors were optimized with the Box–Behnken design, and the most suitable condition for dextranase activity at 30.24 unit/g was achieved with 80 g/L dextran, 30 g/L yeast extract and five day- old inoculum. The use of 0.85% alginate beads for encapsulation exhibited maximum dextranase activity at 25.18 unit/g beads, and this activity was stable in toothpaste for three months of testing. This study explored the potential production of fungal dextranase under optimal conditions and its encapsulation using alginate for the possibility of applying encapsulated dextranase as an additive in toothpaste products for preventing dental caries.

The Marine Catenovulum agarivorans MNH15 and Dextranase: Removing Dental Plaque

Dextranase, a hydrolase that specifically hydrolyzes α-1,6-glucosidic bonds, has been used in the pharmaceutical, food, and biotechnology industries. In this study, the strain of Catenovulum agarivorans MNH15 was screened from marine samples. When the temperature, initial pH, NaCl concentration, and inducer concentration were 30 °C, 8.0, 5 g/L, and 8 g/L, respectively, it yielded more dextranase. The molecular weight of the dextranase was approximately 110 kDa. The maximum enzyme activity was achieved at 40 °C and a pH of 8.0. The enzyme was stable at 30 °C and a pH of 5–9. The metal ion Sr²⁺ enhanced its activity, whereas NH⁴⁺, Co²⁺, Cu²⁺, and Li⁺ had the opposite effect. The dextranase effectively inhibited the formation of biofilm by Streptococcus mutans. Moreover, sodium fluoride, xylitol, and sodium benzoate, all used in dental care products, had no significant effect on dextranase activity. In addition, high-performance liquid chromatography (HPLC) showed that dextran was mainly hydrolyzed to glucose, maltose, and maltoheptaose. The results indicated that dextranase has high application potential in dental products such as toothpaste and mouthwash.

Dextranase from Arthrobacter oxydans KQ11-1 inhibits biofilm formation by polysaccharide hydrolysis

Dental plaque is a biofilm of water-soluble and water-insoluble polysaccharides, produced primarily by Streptococcus mutans. Dextranase can inhibit biofilm formation. Here, a dextranase gene from the marine microorganism Arthrobacter oxydans KQ11-1 is described, and cloned and expressed using E. coli DH5α competent cells. The recombinant enzyme was then purified and its properties were characterized. The optimal temperature and pH were determined to be 60°C and 6.5, respectively. High-performance liquid chromatography data show that the final hydrolysis products were glucose, maltose, maltotriose, and maltotetraose. Thus, dextranase can inhibit the adhesive ability of S. mutans. The minimum biofilm inhibition and reduction concentrations (MBIC₅₀ and MBRC₅₀) of dextranase were 2 U ml^-1 and 5 U ml^-1, respectively. Scanning electron microscopy and confocal laser scanning microscope (CLSM) observations confirmed that dextranase inhibited biofilm formation and removed previously formed biofilms.

Effects of combined exogenous dextranase and sodium fluoride on Streptococcus mutans 25175 monospecies biofilms

PURPOSE

To investigate the effects of exogenous dextranase and sodium fluoride on a S. mutans monospecies biofilm.

METHODS

S. mutans 25175 was grown in tryptone soya broth medium, and biofilm was formed on glass slides with 1.0% sucrose. Exogenous dextranase and sodium fluoride were added alone or together. The biofilm morphology was analyzed by confocal laser scanning microscopy. The effects of the drug on the adhesion and exopolysaccharide production by the biofilms were evaluated by scintillation counting and the anthrone method, respectively.

RESULTS

In this study, we found that the structure of initial biofilm and mature biofilm were partly altered by dextranase and high concentrations of sodium fluoride separately. However, dextranase combined with a low concentration of sodium fluoride could clearly destroy the typical tree-like structure of the biofilm, and led to less bacterial adhesion than when the dextranase or fluoride were used alone (P < 0.05). The amounts of soluble and insoluble exopolysaccharide were significantly reduced by combining dextranase with a low concentration of sodium fluoride, much more than when they were used alone (P < 0.05). These data indicate that dextranase and a low concentration of sodium fluoride may have synergistic effects against S. mutans biofilm and suggest the application of a low concentration of sodium fluoride in anticaries treatment.

Roles of Streptococcus mutans dextranase anchored to the cell wall by sortase

In order to clarify the role that sortase (SrtA) plays in anchoring dextranase (Dex) to the cell wall of Streptococcus mutans, both Dex- and SrtA- mutants were constructed by insertional inactivation of the respective genes. Western blot analysis with a Dex antiserum showed that in the srtA mutant the Dex was not bound to the cell wall but was secreted into the culture supernatant. In contrast, in the wild type, Dex remained cell-wall-associated. Biological properties of the srtA mutant were examined in dextran fermentation, colony morphology and adherence to a smooth surface. The srtA mutant, as well as the wild type, retained the ability to ferment dextran. However, the colony morphology of the srtA mutant on Todd Hewitt agar containing sucrose was much larger than that of the wild type and showed a ring-like structure. In addition, the srtA mutant was more adhesive to a smooth surface than the wild type when sucrose was present. However, the adhesion of the srtA mutant remarkably decreased by addition of exogenous dextranase. These studies suggest that the SrtA mediates Dex-anchoring to the cell wall in S. mutans, and cell wall-anchored Dex plays a role in controlling both the adhesive properties of extracellular glucan and the ability to utilize extracellular glucan as a nutrient source. In contrast, extracellular Dex is only responsible for degrading extracellular glucan as a nutrient source.

The effect of chaya (Cnidoscolus aconitifolius) leaf meal and of exogenous enzymes on amino acid digestibility in broilers

1. The apparent ileal nitrogen (N) and amino acid digestibilities in chaya leaf meal (CLM) (Cnidoscolus aconitifolius) with added enzymes, and the same variables in diets containing different amounts of CLM were studied in chickens. 2. In the first experiment pectinase, beta-glucanase, and pectinase + beta-glucanase were added to CLM. In the second experiment, there were three diets based on maize and soybean: 0, 150 and 250 g/kg CLM. 3. Pectinase significantly increased both lysine and overall amino acid digestibilities in CLM. 4. In experiment 2, the amino acid digestibility in birds fed on CLM250 was lower than that from birds fed on either control or CLM150. Only the digestibilities of alanine, arginine and proline were lower in birds fed on CLM150 than in those fed on the control diet. Nitrogen digestibility was lower in birds fed on the CLM250 diet than on either control or CLM150 diets. These findings were attributed to the increasing concentration of fibre with increasing dietary CLM.

Effect of enzyme preparation containing xylanase and beta-glucanase on performance of laying hens fed wheat/barley- or maize/soybean meal-based diets

1. A commercial enzyme preparation (Quatrazyme HP) containing xylanase and beta-glucanase was examined in two laying hen experiments with wheat/barley- or maize-based diets. The activities of other enzymes were measured also. Starch, cell wall contents and effects of Quatrazyme HP on in vitro viscosity of wheat, barley, maize and soybean meal were determined. 2. In the first experiment, 90 ISA Brown laying hens at 28 weeks of age were given a wheat/barley basal diet with or without 20mg of Quatrazyme HP, which provided 560 and 2,800 IU of xylanase and beta-glucanase/kg diet. In the second experiment, 66 ISA Brown laying hens at 45 weeks of age were given a maize/soybean meal basal diet with or without 20 mg of Quatrazyme HP/kg diet for 9 weeks. Egg production, egg weight, egg mass, feed conversion ratio and change in body weight were recorded as response criteria. 3. There was a significant improvement in feed conversion ratio with enzyme supplementation. Birds given an enzyme-supplemented diet gained 86 g while those fed on the unsupplemented diet lost 103 g of their body weight by the end of the experiment. 4. The enzyme preparation did not affect either egg production, egg weight or egg mass of birds fed on the maize/soybean meal diet. However, a significant improvement in feed conversion ratio was detected. Birds on either the supplemented or unsupplemented diet exhibited an increase in their body weight at the end of the experiment. 5. Addition of xylanase and beta-glucanase decreased in vitro viscosity of wheat, barley, maize and soybean meal. This effect was greater for wheat and barley than for maize and soybean meal. 6. It was concluded that the beneficial effect of using an enzyme preparation containing xylanase and beta-glucanase is not limited to wheat/barley-based diets but also occurs with maize/soybean meal-based diets.

Mushrooms, tumors, and immunity

Medicinal properties have been attributed to mushrooms for thousands of years. Mushroom extracts are widely sold as nutritional supplements and touted as beneficial for health. Yet, there has not been a critical review attempting to integrate their nutraceutical potential with basic science. Relatively few studies are available on the biologic effects of mushroom consumption, and those have been performed exclusively in murine models. In this paper, we review existing data on the mechanism of whole mushrooms and isolated mushroom compounds, in particular (1-->3)-beta-D-glucans, and the means by which they modulate the immune system and potentially exert tumor-inhibitory effects. We believe that the antitumor mechanisms of several species of whole mushrooms as well as of polysaccharides isolated from Lentinus edodes, Schizophyllum commune, Grifola frondosa, and Sclerotinia sclerotiorum are mediated largely by T cells and macrophages. Despite the structural and functional similarities of these glucans, they differ in their effectiveness against specific tumors and in their ability to elicit various cellular responses, particularly cytokine expression and production. Unfortunately, our data base on the involvement of these important mediators is still rather limited, as are studies concerning the molecular mechanisms of the interactions of glucans with their target cells. As long as it remains unclear what receptors are involved in, and what downstream events are triggered by, the binding of these glucans to their target cells, it will be difficult to make further progress in understanding not only their antitumor mechanisms but also their other biological activities.

Dextranase enhances antibiotic efficacy in experimental viridans streptococcal endocarditis

In endocarditis, exopolysaccharide production by viridans streptococci has been associated with delayed antimicrobial efficacy in cardiac vegetations. We compared the efficacies of temafloxacin alone and in combination with dextranase, an enzyme capable of hydrolyzing 20 to 90% of the bacterial glycocalyx, in a rabbit model of endocarditis. In in vivo experiments, rabbits were infected intravenously with 10(8) Streptococcus sanguis organisms and were treated 6 days later with temafloxacin (50 mg/kg of body weight intramuscularly twice a day) alone or combined with dextranase (1,000 U per rabbit per day intravenously). After 4 days of treatment (day 11), the animals were sacrificed and vegetations were quantitatively cultured. For ex vivo experiments, rabbits were infected as stated above and, on day 11, vegetations were excised aseptically and incubated in vitro in rabbit serum alone (control) or with temafloxacin or temafloxacin plus dextranase at concentrations similar to peak levels in plasma. In vitro, dextranase alone had no antimicrobial effect. In vivo and ex vivo, temafloxacin combined with dextranase was more effective than temafloxacin alone (P < 0.05). Our results suggest that dextranase is able to increase the effects of temafloxacin by reducing the amount of bacterial glycocalyx in infected vegetations, as confirmed in vitro by electron microscopy showing a markedly reduced amount of glycocalyx and a more clearly visible fibrin matrix.

Glucans synthesized in situ in experimental salivary pellicle function as specific binding sites for Streptococcus mutans

Many researchers have suggested that the role of glucan-mediated interactions in the adherence of Streptococcus mutans is restricted to accumulation of this cariogenic bacterium following its sucrose (i.e., glucan)-independent binding to saliva-coated tooth surfaces. However, the presence of enzymatically active glucosyltransferase in salivary pellicle suggests that glucans could also promote the initial adherence of S. mutans to the teeth. In the present study, the commonly used hydroxyapatite adherence assay was modified to include the incorporation of glucosyltransferase and the synthesis of glucans in situ on saliva-coated hydroxyapatite beads. Several laboratory strains and clinical isolates of S. mutans were examined for their ability to adhere to experimental pellicles, either with or without the prior formation of glucans in situ. Results showed that most strains of S. mutans bound stereospecifically to glucans synthesized in pellicle. Inhibition studies with various polysaccharides and fungal dextranase indicated that alpha 1,6-linked glucose residues were of primary importance in the glucan binding observed. Scanning electron microscopic analysis showed direct binding of S. mutans to hydroxyapatite surface-associated polysaccharide and revealed no evidence of trapping or cell-to-cell binding. S. mutans strains also attached to host-derived structures in experimental pellicles, and the data suggest that the bacterial adhesins which recognize salivary binding sites were distinct from glucan-binding adhesins. Furthermore, glucans formed in experimental pellicles appeared to mask the host-derived components. These results support the concept that glucans synthesized in salivary pellicle can promote the selective adherence of the cariogenic streptococci which colonize human teeth.

Increasing the plasma half-life of trichosanthin by coupling to dextran

Trichosanthin (TCS) is a plant protein which has a wide spectrum of pharmacological activities. It was demonstrated recently that this compound suppressed the replication of human immunodeficiency virus (HIV-1) in vitro. The mechanism of action is believed to be inhibition of protein synthesis. Trichosanthin is a low molecular weight protein which is expected to be easily filtered and eliminated through the kidney. To minimize renal loss, the molecular size of trichosanthin can be increased by coupling to dextran. The larger complex will not undergo glomerular filtration and therefore renal loss can be prevented. This study investigates the kidney's role in trichosanthin elimination and the beneficial effect afforded by coupling to dextran in prolonging plasma half-life. For this purpose, a radioimmunoassay has been developed to determine the concentration of TCS in plasma and urine. The sensitivity of this assay is in the nanogram range. Trichosanthin was coupled to dextran T40 by a dialdehyde method and successful coupling was confirmed by gel filtration chromatography. The complex retained specific binding to trichosanthin antibodies with decreased affinity which can be partially reversed after incubation with dextranase; an enzyme that digested dextran. The pharmacokinetics of intravenously administered trichosanthin (0.75 mg/kg) was compared between two groups of rats with normal and impaired renal function (bilateral renal arterial ligation). Rats with ligation showed a decrease in plasma clearance from 4780 +/- 570 to 220 +/- 20 microL/min and an increase in the mean residence time from 9 +/- 1 to 145 +/- 16 min. Despite the several-fold difference in these parameters, recovery of trichosanthin from normal rat urine was only 0.38 +/- 0.05%. This value can be increased by using higher injection doses. The data indicate that the kidney is an important organ for the elimination of trichosanthin. When the dextran-trichosanthin complex was injected into normal rats trichosanthin activity was not detected in the urine. All the pharmacokinetic parameters suggest that the dextran-trichosanthin complex stayed longer in the body and maintained a much higher plasma concentration than trichosanthin.

Clindamycin effect on glycocalyx production in experimental viridans streptococcal endocarditis

Abundant glycocalyx production by viridans streptococci in the rabbit model of endocarditis has been associated with delayed antimicrobial sterilization. Enzymatic digestion of the glycocalyx with dextranase enhances antibiotic activity. The effect of clindamycin (30 mg/kg, subcutaneous, three times daily) was studied in rabbits with experimental aortic valve endocarditis caused by high glycocalyx-producing viridans streptococci. Animals receiving clindamycin had smaller vegetations that were sterilized more quickly than did controls or animals receiving penicillin or dextranase alone (P less than .001). Penicillin plus dextranase treatment allowed greater bacterial killing than penicillin alone and did not differ significantly from clindamycin treatment. Electron micrographs revealed markedly less cell-adherent glycocalyx on organisms grown in vitro treated with clindamycin versus penicillin and controls. It is hypothesized that clindamycin inhibits glycocalyx production in vivo, allowing better antimicrobial penetration in the infected cardiac vegetation.

Induction of antibody response by antigen conjugates and E. coli lipopolysaccharide in mice tolerant to dextran B-512

Three groups of mice were made tolerant to dextran (Dex) with one of three schedules: a) an immunogenic dose of 10 micrograms three times a week for 26 weeks; b) an immunogenic dose of 50 micrograms three times a week for two weeks, and c) a single tolerogenic dose of 10 mg. Prior to tolerance induction, continuous administration of 10 micrograms Dex induced a predominantly IgM antibody response. The tolerant mice were then challenged with immunogenic doses of the dextran conjugates Dex-Salmonella typhi (Dex-S. typhi) and Dex-sheep red blood cells (Dex-SRBC), and with E. coli lipopolysaccharide (LPS). IgM and IgG responses were compared in each group. Immunogenic dextran alone did not induce a response in the 1 tolerant mice. The response induced by Dex-S. typhi or Dex-SRBC was low but LPS induced an elevated anti-Dex SFC in the three groups of resistant mice. The antibody responses were not affected by pretreatment of antigen with dextranase. Loss of tolerance was more pronounced in mice made tolerant by continuous stimulation as compared to mice made tolerant by a single large dose of antigen. Thus, LPS is able to induce specific responses from B cells of tolerant animals. Furthermore, the level of response was dependent on the toleration schedule.

Analysis of the mechanism of recognition in the complement alternative pathway using C3b-bound low molecular weight polysaccharides

The human complement (C) system recognizes bacterial, fungal and viral activators of the alternative pathway following covalent attachment of the protein C3b to carbohydrates (CHO) on the surface of the organisms. Recognition first manifests itself as a 3- to 10-fold reduction in the affinity of C3b for factor H, a regulatory protein of C. This report describes the use of a fluorimetric assay which is sensitive to the C3b-H interaction to study the characteristics of recognition. Fluid phase C3b covalently bound to CHO (C3b-CHO) was prepared by activating C3 in the presence of the small homopolymers dextran (alpha 1-6 polyglucose) or inulin (beta 1-2 polyfructose). In particulate form both polysaccharides are activators of C. The conjugates exhibited increased resistance to inactivation in the factor H-dependent assays compared to C3b not bound to CHO and to C3b bound to mono- or disaccharides. The dextran-induced restriction of inactivation was partially reversed by treatment of the conjugate with dextranase. C3b-CHO conjugates failed to bind to factor H-Sepharose and when introduced into serum behaved as though C3b was attached to particulate activators of C, suggesting that the fluorimetric assay accurately reports recognition. The results suggest that the recognition site which induces a reduction in the affinity of C3b for factor H is distinct from the thioester site of C3b and can recognize structural features of polysaccharides including size, sialic acid content, and possibly aspects of three-dimensional oligosaccharide structure.

In vitro inhibition of adherence of Streptococcus mutans strains by nonadherent mutants of S. mutans 6715

Four nonadherent mutants from Streptococcus mutans 6715 mutant UAB66 (serotype g) with similar phenotypes were shown to inhibit the adherence of adherence-proficient S. mutans serotypes c and g strains. One mutant, UAB108, was shown to inhibit adherence by wild-type strains representing serotypes a, d, and e as well. This inhibition of adherence was seen with pairs of strains grown in partially defined (PD) medium supplemented with 1% sucrose in both microtiter plates and glass tubes. The inhibiting factor was present in culture supernatant fluids of inhibiting strains grown in PD medium plus 1% sucrose and was heat stable. Ethanol precipitation of culture supernatant fluids of these strains yielded a water-soluble polymer which effectively inhibited the adherence of UAB66. This polymer, isolated from UAB108, was also shown to inhibit the adherence of UAB66 at lower concentrations than that needed to inhibit adherence with dextran T10. Partially purified glucosyltransferase, isolated from the culture supernatant fluids of glucose-grown UAB108, produced a water-soluble glucan which was shown to inhibit the adherence of UAB66 as well. The methods developed permit rapid screening for strains or mutants of strains or both that inhibit adherence or plaque formation or both by wild-type strains of S. mutans.

Biodegradable microspheres. I. Duration of action of dextranase entrapped in polyacrylstarch microparticles in vivo

Dextranase was entrapped in polyacryl starch microspheres of different compositions by emulsion polymerization. After i.v. injection in mice and rats, the particles were removed from the blood circulation by macrophages of the reticuloendothelial system. In these cells, the particles are accumulated in the lysosomes. The degradation of different 14C-labeled microparticles and their entrapped dextranase was followed in an isolated lysosomal fraction in vitro and in liver and spleen after i.v. injection in mice. The duration of entrapped dextranase in vivo was followed directly, i.e., by an enzyme assay, and indirectly by following the decrease of a stored material, [3H]dextran in the liver. The degradation of the entrapped enzyme was dependent on the composition of the particle matrix. More cross-linked spheres could better protect the entrapped enzyme in vitro and in vivo. The half-life of free dextranase in the lysosomal fraction was estimated to be about 4 hr, whereas the duration of entrapped dextranase in the liver was at least 48 hr, as measured with [3H]dextran. Finally, the effect of entrapped and free dextranase on an artificially induced storage disease was studied. The stored [3H]dextran was eliminated completely when dextranase was used in microparticles, whereas free dextranase had no effect in vivo.

Ontogenic development of the suppressed secondary response to native dextran

The ontogenic development of the plaque-forming cell (PFC) response to the thymus-independent (TI) antigen alpha 1-6 native dextran B512 was studied to determine when the first minimal amounts of anti-dextran antibodies are formed. Substantial antibody responses to certain other TI polysaccharide antigens arise during the first month of life, whereas the development of the response to native dextran has been found to be conspicuously delayed in high-responder mice. Results indicated that CBA mice began to produce minimal amounts of anti-dextran antibodies between 15 and 21 days of age, and the development continued progressively until peak levels were reached at 90 days of age. The alpha 1-6 native dextran system is also one of the few murine models in which endogenous anti-idiotypic antibodies are formed subsequent to anti-dextran production. It has been shown that the anti-idiotypic antibodies are responsible for specific inhibition of secondary PFC responses to dextran. Suppression of the secondary response was used here to ascertain whether the initial low level of anti-dextran antibodies elicited in 15-day-old animals was sufficient to lead to inhibition of the secondary response. The approach confirmed the initiation of anti-dextran production at 15-21 days of age and indicated that the small amount of anti-dextran antibodies produced at this age was sufficient to induce the mechanism leading to suppression of the secondary response.

Induction and persistence of B-cell tolerance to the thymus-dependent component of the alpha(1 leads to 6) glucosyl determinant of dextran. Recovery induced by treatment with dextranase in vivo

A direct comparison was made between thymus-dependent (TD) and thymus-independent (TI) responses in mice tolerized for (1 leads to 6) glycosyl determinants by the injection of dextran B512. Long-lasting B-cell tolerance by dextran was reversed when mice were treated with dextranase in vivo. Complete or partial reversion of tolerance with the enzyme was invariably obtained for the TI response but the TD component proved to be more resistant and dependent on the immunogen used to test the reversion. The uniformity of the spectrotype in BALB/c mice, even under conditions of partial tolerance, permitted the analysis by isoelectric focussing of serum from tolerant mice treated with dextranase and immunized with TD dextran-ovalbumin. Results showed that, with one single exception, mice thus treated produced spectrotypes no different from the pattern normally found in immune animals. The results presented suggest that at least some alpha(1 leads to 6) specific B cells, both TD and TI, persist in tolerized mice for at least 2 weeks after tolerance induction and they do not support the concept of clonal elimination for either TI or TD responses in adult mice.

Adherence of Streptococcus sanguis clinical isolates to smooth surfaces and interactions of the isolates with Streptococcus mutans glucosyltransferase

Streptococcus sanguis isolated from human dental plaque were grown in Todd-Hewitt broth. Cells were collected by centrifugation and lyophilized after extensive washing with water. The cell-associated glucosyltransferase (GTase) activities of S. sanguis strains were assayed with [14C]sucrose. Strain differences in GTase activity were significant within the same serotype or biotype or both. The ability of S. sanguis cells to adhere to smooth glass surfaces was generally weak, irrespective of significant cell-associated GTase activity synthesizing water-insoluble, gel-like glucans. Resting cells of most S. sanguis strains bound extracellular GTase from Streptococcus mutans strain B13 (serotype d), resulting in the strong adherence of the S. sanguis cells to smooth glass surfaces in the presence of sucrose. Conversely, S. mutans B13 cells also could bind extracellular GTase from some strains of S. sanguis examined. The sucrose-dependent adherence of S. mutans cells was not altered, although S. sanguis strains from which the extracellular GTases were obtained did not produce significant adherence in the presence of sucrose. In view of these findings, it was suggested that S. mutans GTase could affect the adherence of S. sanguis to smooth tooth surfaces in the oral cavity.

Effects of dextranases on attachment of Streptococcus mutans to hydroxyapatite

A Fusarium dextranase and a Penicillium dextranase were compared for their relative ability to quantitatively reduce the adsorption of (3)H-labeled Steptococcus mutans cells onto hydroxyapatite. Fusarium dextranase-treated hydroxyapatite disks caused a statistically significant decrease in the hydroxyapatite adsorption of both the OMZ 176 and NCTC 10449 strains of S. mutans relative to untreated control disks. The extent of initial bacterial adsorption was not promoted by sucrose-dependent glucan synthesis. Since the Fusarium dextranase has a much greater affinity for hydroxyapatite than the Penicillium dextranase, it could represent an enzyme with improved decay-preventive therapeutic properties. This was concluded because the Fusarium dextranase may interfere with both the initial attachment and later glucan-dependent accumulation of dental plaque microorganisms.

Specificity of coaggregation reactions between human oral streptococci and strains of Actinomyces viscosus or Actinomyces naeslundii

Coaggregation reactions between actinomycete and streptococcal cells occurred frequently when human strains of Actinomyces viscosus or A. naeslundii were mixed with human isolates of Streptococcus sanguis or S. mitis, but were infrequent with other oral actinomycetes and streptococci. Two groups of actinomycetes and four groups of streptococci were defined by the patterns of their coaggregation reactions and by the ability of beta-linked galactosides (i.e., lactose) to reverse these reactions. Coaggregations occurred by one of the following three kinds to cell-cell interactions: (i) coaggregation that was blocked by heating the streptococcus but not the actinomycete and was not reversed by lactose; (ii) coaggregation that was blocked by heating the actinomycete but not the streptococcus and was reversed by lactose; and (iii) coaggregation that was blocked only by heating both cell types. The latter reaction was a combination of the first two since lactose reversed coaggregation between heated streptococci and unheated actinomycetes but did not reverse coaggregations between unheated streptococci and heated actinomycetes. Cells that could be heat inactivated also were inactivated by amino group acetylation or protease digestion, whereas cells that were unaffected by heat were not inactivated by these treatments. Coaggregation reactions of each kind were Ca2+ dependent and insensitive to dextranase treatment. These findings are consistent with the hypothesis that human strains of A. viscosus and A. naeslundii coaggregate with strains of S. sanguis and S. mitis by a system of specific cell surface interactions between protein or glycoprotein receptors on one cell type and carbohydrates on the other type.

Lectin analysis of Trypanosoma congolense bloodstream trypomastigote and culture procyclic surface saccharides by agglutination and electron microscopic technics

Living, intact bloodstream trypomastigotes and culture procyclic forms of Trypanosoma congolense were tested for aggulination with the lectins concanavalin A (Con A), phytohemagglutinin P (PP), wheat germ agglutinin (WGA), soybean agglutinin (SBA), and fucose binding protein (FBP). Similar experiments were conducted with living bloodstream and culture forms treated with trypsin or dextranase. Parasites were incubated for 30 min at 25 C in various concentrations of each lectin, then examined for agglutination by dark-field microscopy. Control preparations consisted of parasites incubated alone or with 0.5 M of the specific competing sugar, with or without the corresponding lectin. Electron-microscopic localization of lectin binding sites on the surface of intact and dextranase-treated bloodstream and intact culture forms was accomplished with Con A, reacted with horseradish peroxidase (HRP) and then diaminobenzidine (DAB). In addition, FBP and SBA were coupled to HRP, then utilized for the localization of binding saccharides on the surface of bloodstream forms by the DAB technic. Similar studies were conducted with culture procyclics incubated with WGA-, SBA-, PP- or FBP-HRP conjugates and then reacted with DAB. Controls were utilized to confirm the sugar specificity of all positive reactions. Intact living bloodstream forms were agglutinated in a concentration-dependent manner with all the lectins tested. Agglutination levels were scored as Con A greater than FBP greater than WGA = PP = SBA. Sugars resembling alpha-D-mannose, N-acetyl-D-glucosamine, N-acetyl-D-galactosamine, and alpha-L-fucose are evidently present on the surface of the parasites. No agglutination was noted in any control preparations. Identical lectin-induced agglutinations were obtained with trypsin- or dextranase-treated bloodstream forms. Trypsin disrupted but did not entirely remove the surface coat of bloodstream forms, while dextranase did not alter the ultrastructure of the parasites. Con A-, SBA- and FBP-binding saccharides were distributed uniformly on the surface coat of intact bloodstream forms; a similar distribution of Con A receptors was noted also on the surface of dextranase-treated cells. No lectin-binding saccharides were visualized by electron microscopy on any control preparations. Intact, trypsin- or dextranase-treated, procyclics were agglutinated in a concentration-dependent fashion by Con A and WGA, but not by the other lectins tested. Control preparations did not agglutinate and the enzymes did not affect the ultrastructure of the parasites. Con A- and WGA-specifically binding saccharides were uniformly distributed on intact procyclics and control preparations were lectin-negative. Thus, T. congolense procyclics retained surface saccharides resembling alpha-D-mannose and N-acetyl-D-glucosamine but lost sugars resembling N-acetyl-D-galactosamine (or D-galactose) and alpha-L-fucose...

Reversal of B-cell immunization or tolerization by specific enzymatic degradation of antigen

The mechanism of B-cell immunity or tolerance reversal by enzymatic treatment, was studied on cells stimulated in vitro by T-independent antigens, either sensitive or insensitive to enzymatic hydrolysis. B-cell stimulation induced by spleen cell incubation with DNP coupled to polymer was reversed when antigen-pulsed cells were treated with enzymes specifically hydrolytic for the carrier. Cell treatment with proteases abolished the response induced by DNP-POL (polymerized flagellin). Immunity or tolerance remained unchanged when induced by DNP conjugated to D-GL (D-glutamic and D-lysine copolymer) or to dextran B512 or B1299. While DNP-POL is a substrate for proteases, the latter three components are insensitive to the hydrolytic action of protease. B cells, preincubated with DNP-B512, were rescued from tolerance by dextranase treatment. Immunity and tolerance remained unchanged when induced by DNP-POL, DNP-B512 and DNP-B1299. While DNP-B512 was totally hydrolysed by dextranase, the latter three conjugates were not. These results show that (a) the initial stage for the induction of either immunity or tolerance is reversible, (b) the target of the enzymatic effect is the antigen itself, and (c) the interaction between polymeric antigen and B-cell Ig receptors is not sufficient to drive the cell to an irreversible stage of differentiation.

Immunological tolerance to the thymus-independent antigen dextran can be abrogated by thymus-dependent dextran conjugates: evidence against clonal deletion as the mechanism of tolerance induction

Tolerance to the alpha1--6 epitope of native dextran B512 was found to be very stable and could not be broken by the injection of dextran conjugated to several substances, such as protein A, keyhole limpet haemocyanin, edistin, concanvalin A or Staphylococcus bacteria, strain Cowan. However, when tolerant mice were injected with dextranase, all the above conjugates induced a strong anti-alpha1--6 immune response. In contrast, native dextran itself never induced a response in tolerant, dextranase-treated mice. It was concluded that tolerance only affects the specific B-cell subpopulation that can respond to the polyclonal B-cell-activating (PBA) property of dextran, whereas other specific B cells having PBA receptors for, e.g., signals delivered by collaborating T cells remain in a resting state. These B cells can respond in a specific immune response against the tolerogen after removal of the antigen, which blocks the Ig receptors and therefore prevents them from passively focusing the antigen. Thus, immunological tolerance is not caused by clonal elimination of the antigen-specific clone, but only affects a small subfraction of cells with Ig receptors against the tolerogen.

Effect of dextranase on plaque formation and caries development in the rat

Plaque formation and caries development were studied in 0-M rats fed Diet 2000 and infected with S. mutans 6715 and fecal flora from older caries-active rats. Merck dextranase, Beckman dextranase or Beckman glucanase 447 were administered singly or in combination to groups of 12 rats either as an addition to the diet or as a "mouthwash" twice daily, 5 per week. All enzymes studied were associated with significant inhibition of both plaque formation and caries development, especially on the buccal and lingual surfaces.

Irreversible immunological tolerance to thymus-independent antigens is restricted to the clone of B cells having both Ig and PBA receptors for the tolerogen

Mice were tolerized to the alpha1-6 epitope of native dextran. When their spleen cells were removed and activated by LPS, they did not synthesize antibodies against the tolerogen. However, when cells from tolerant mice were treated with dextranase or left untreated in culture for 24 h they were activated by LPS to the synthesis of antibodies against the tolerogen. When 24 h tolerized lymphocytes were treated with dextranase and transferred with immunogenic doses of dextran to irradiated mice they failed to produce antibodies against the tolerogen. In contrast, cells incubated with dextran for 2 h and thereafter dextranase treated were readily immunized by dextran in the same system. It is concluded that only the B cell clones having both Ig receptors and PBA receptors for the tolerogen become irreversibly tolerized, whereas B cells having Ig receptors for a different PBA are not tolerized, but remain in a resting state, even though their Ig receptors have bound the tolerogen.

[Action of various beta(1-3)-D-glucanases on the wall of yeasts: taxonomic applications]

Purified beta-(1-3)-D-glucanases (from Aspergillus nidulans, Badidiomycetes sp. QM 806, Trichoderma viride) are used to release protoplasts from various yeasts. Two of them may prove taxonomic correlation. The enzyme of Basidomycetes sp. releases protoplasts from Ascomycetes, the enzyme of T. viride releases protoplasts from Ascomycetes and Heterobasidiomycetes; none of them acts on the Basidiomycetes.

Analysis of the dextranase activity produced by an oral strain of Bacteroides ochraceus

An anaerobic, gram-negative, dextranase-producing filamentous bacterium isolated from human dental plaque has been identified as a strain of Bacteroides ochraceus. The inducible intracellular dextran-degrading activities produced by this microoranism can be fractionated into endohydrolytic and exohydrolytic enzymes with distinct pH optima. These enzymes reduce the apparent rate of glucan production from sucrose by the dextransucrase produced by Streptococcus mutans and consequently may influence the in vivo production of polysaccharides involved in plaque accumulation and metabolism.

Dextran-mediated interbacterial aggregation between dextran-synthesizing streptococci and Actinomyces viscosus

Streptococcus sanguis and Streptococcus mutans bind to the surface of Actinomyces viscosus, producing large microbial aggregates. Aggregates form rapidly and are not easily dissociated by vigorous mixing. The binding is mediated by dextran. Glucose-grown streptococci will not aggregate unless they are first mixed with high-molecular-weight dextran. Aggregation is induced with dextrans isolated from Leuconostoc, S. sanguis, or S. mutans. Sucrose-grown streptococci will adhere to A. viscosus without the addition of an exogenous source of dextran. A. viscosus will bind dextran and then bind glucose-grown streptococci. Aggregation occurs over a wide pH range and is dependent on cations. The aggregating activity of A. viscosus is both protease and heat sensitive. The aggregating activity of S. sanguis is heat stable but sensitive to dextranase.

Multicomponent nature of the glucosyltransferase system of Streptococcus mutans

The glucosyltransferases of S mutans 6715 were resolved into two major fractions. One fraction synthesized water-soluble glucans and the other made water-insoluble glucans. Each fraction was found by polyacrylamide gel electrophoresis to be composed of several catalytically active species, apparently glycoprotein in nature. Treatment of the glucosyltransferases with dextranase in the absence of sucrose caused an interconversion of enzyme forms concomitant with a time-dependent loss of enzyme activity, but did not appear to remove significant amounts of the carbohydrate associated with the enzymes. Comparison of enzyme activity patterns on polyacrylamide gels of the five different S mutans serotypes further emphasizes the complexity of the glucosyltransferase system from this group of microorganisms.

Effect of dextranase on the extracellular polysaccharide synthesis of Streptococcus mutans; chemical and scanning electron microscopy studies

A dextranase preparation (AD17) partially purified from a culture liquor of Spicaria violacea strain IFO 6120 significantly inhibited the formation of artifcial dental plaque on a steel wire or on an extracted tooth surface. Changes in the surface morphology of Streptococcus mutans cells due to AD17 action were studied using scanning electron microscopy. S. mutans cells grown in 5% sucrose-containing broth were coated with sticky amorphous capsule-like material, whereas cells grown in sucrose in the presence of AD17 or in glucose instead of sucrose did not synthesize such capsular material. AK17 degraded commercially available dextrans of molecular weight 7 X 1(04) and 2 X 10(6) to liberate glucose and various oligosaccharides, including isomaltose. On the other hand, AD17 hydrolyzed the extracellular polysaccharides (mainly glucan in nature) of some strains of S. mutans to a limited degree. Only 15 to 36% of the total polysaccharides were hydrolyzed by AD1M with little release of isomaltose. Prolonged incubation of the polysaccharides from S. mutans with AD17 did not release additional reducing sugars, which indicates that AD17 did not contain alpha-1,3-glucanase activity. These results suggest that glucosidic linkages which are susceptible to AD17 may play an important role in the adherence of S. mutans cells to smooth surfaces.

Cell surface saccharides of Trypanosoma lewisi. I. Polycation-induced cell agglutination and fine-structure cytochemistry

Trypanosoma lewisi bloodstream and culture forms were agglutinated differentially with low concentrations of the cationic compounds: ruthenium red, ruthenium violet, Alcian blue chloride, 1-hexadecylpyridinium chloride, lanthanum chloride, and cationized ferritin. The bloodstream form trypanosomes gave the highest agglutination levels with each of the compounds tested. Ruthenium red was the most effective inducer of cell agglutination among the several cations used. Trypsin-treated bloodstream forms were agglutinated less in the presence of ruthenium red than untreated controls. Ruthenium red-induced cell agglutination also was lowered with chondroitin sulphate and dextran sulphate, but not with alpha-D-glucose, alpha-D-mannose or with several methyl glycosides. Treatment of the bloodstream trypanosomes with alpha-amylase, dextranase, or neuraminidase had little effect on agglutination levels obtained with ruthenium red. Fine-structure cytochemical staining with ruthenium red, ruthenium violet, and Alcian blue-lanthanum nitrate was used to ascertain the presence and distribution of presumptive carbohydrates in the trypanosome cell surface. The extracellular surface coat of the bloodstream forms stained densely with each of the polycationic dyes. Trypsin treatment removed the surface coat from bloodstream trypanosomes; however, the surface membranes of the organisms were stained densely with the several dyes. Similar surface-membrane staining was obtained with the cationic compounds and the culture forms, which lack a cell surface coat. Cationized ferrin was used at the fine-structure level to visualize the negative surface charge present in the cell surface coat and external membrane of the several trypanosome stages. Results obrained from the agglutination and cytochemistry experiments indicate that complex polysaccharides are present in the surface membranes and cell surface coat of T. lewisi bloodstream forms. Similar conclusions also pertain to the surface membranes of the T. lewisi culture from trypanosomes. The carbohydrates probably represent glycopeptide and glycoprotein structural components of the surface membrane of this organism.