Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Alginates”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,297 records · Page 72Linked to original sources
PubMed1995

Purification and characterization of the recombinant alginate lyase from Pseudomonas sp. leaked by Escherichia coli upon addition of glycine.

The plasmid pAL205 encodes an alginate lyase gene of Pseudomonas sp. OS-ALG-9, fused in frame to the beta-galactosidase alpha-peptide gene. The alginate lyase (Aly) expressed in Escherichia coli (pAL205) was significantly secreted into the medium by the addition of glycine. The extracellular enzyme isolated from the culture of E. coli JM109 (pAL205) was purified over 15,000-fold by successive chromatography and subjected to amino acid sequence analysis. The sequence determined was identical to that of the intracellular protein. Since the activity and molecular size of the extracellular Aly is identical to the intracellular protein and to the Aly isolated from Pseudomonas, the glycine does not affect or modify the Aly during its leakage into the medium.

Alginates↗
PubMed2001

Physiological difference during ethanol fermentation between calcium alginate-immobilized Candida tropicalis and Saccharomyces cerevisiae.

Calcium alginate-immobilized Candida tropicalis and Saccharomyces cerevisiae are compared for glucose fermentation. Immobilized C. tropicalis cells showed a slight morphological alteration during ethanol production at 40 degrees C, but their fermentation capacity was reduced by 25%. Under immobilization conditions, the two species demonstrated two different mathematical patterns when the relationship between growth rate, respiration rate, and ethanol tolerance was assessed. The interspecific difference in behavior of immobilized yeast cells is mainly due to their natural metabolic preference. The production of CO(2) by calcium alginate-immobilized C. tropicalis, as well as the lower supply of oxygen to the cells, are the major factors that reduce ethanol production.

Alginates↗
PubMed1985

Diffusion of fluoride from alginate compared with other topical fluoride agents.

A two-chamber diffusion cell has been employed to monitor the diffusion of fluoride (F) from F-containing agents. The F which diffused from fluoridated alginate-base formula, F-containing gel (Gelution) and varnish (Duraphat) was determined within the first 6 or 20 min in unstirred conditions. A comparative analysis of the data showed that the alginate-base formula was efficient in releasing F. The results also indicate that the diffused F was not directly related to the total F content in the products or the bulkiness of the test specimens. It is obvious that the physicochemical properties of the products play a determining role in the release of F.

Acidulated Phosphate Fluoride↗
PubMed1989

Effect of disinfecting solutions on accuracy of alginate and elastomeric impressions.

The effect of immersion in six disinfecting solutions on the accuracy of 10 impression materials was investigated. Impressions were taken of a truncated steel cone. After setting, the impressions were either stored at room temperature for 24 h, for control, or immediately immersed in a disinfecting agent for 60 min (in one case 10 min), and after 24 h poured with gypsum. A steel ring fitting the steel cone was placed on the resulting dies, and the discrepancy between the top surface of the ring and the die was measured. From these measurements the deviation between the base diameter of the die and of the impression was calculated to express the inaccuracy. All impressions except some in Blueprint exhibited a net shrinkage, giving rise to too large die stones and incomplete seating of the steel ring. Blueprint impressions, however, occasionally swelled and resulted in too small die stones and "overseating" of the steel ring. The disinfecting solutions had no significant impact on two impression materials. For the remaining eight materials the accuracy was decreased, increased, or unaffected by the immersion. Generally, the accuracy of the alginates investigated were more affected by the disinfecting solutions than were the elastomeric impression materials. The accuracy of the three alginates was drastically impaired by immersion in 70% ethanol, whereas the remaining five disinfecting solutions had a smaller, though sometimes statistically significant, effect on the accuracy. For the elastomeric materials only a few specific combinations of impression material and disinfecting solution reduced the accuracy.(ABSTRACT TRUNCATED AT 250 WORDS)

Alginates↗
PubMed1998

Experimental actinomycosis in mice induced by alginate gel particles containing Actinomyces israelii.

The present study aimed to make an animal model for investigating chronic infection. Bacterial cells of Actinomyces israelii (ATCC 10048) were packed in alginate gel particles and injected intra-peritoneally into BALB/c mice. Actinomycotic lesions were induced efficiently in 9 mice out of 12 after 3 or 9 weeks. Actinomycotic lesions were not produced by injecting a bacterial suspension of A. israelii except in one animal. Neither did injection of gel particles without bacteria induce lesions. Bacteria survived in the lesions for at least 9 weeks after the injection, and serum IgG levels against the bacteria were significantly elevated in the animals, indicating that the bacteria were protected from immunological elimination and activated humoral immunity in the animals. Histopathological observation of the lesion by staining revealed that the bacteria in the lesions were acid-fast and seemed to become resistant to phagocytosis. The bacterial masses were surrounded by inflammatory cells, including polymorphonuclear leukocytes and macrophages, and were separated from the host cells by a fringe-like structure similar to the capsular structure of natural sulfur granules. The present study indicated that the use of an alginate gel was effective in inducing actinomycotic lesions in mice.

Actinomyces↗
PubMed1990

The effects of disinfectants on the dimensional stability of alginate impression materials.

Glutaraldehyde and hypochlorite solutions have been shown to be effective disinfectants for use in the dental surgery. However, their use in the disinfecting of alginate hydrocolloid impression materials must be open to question since these materials are dimensionally unstable when immersed in aqueous solutions for any length of time. This project investigated the dimensional changes noted in casts poured into alginate impressions which had been stored for up to 60 minutes in either hypochlorite or glutaraldehyde solutions. All changes measured were considered to be within clinical tolerance.

Alginates↗
PubMed1992

Two types of bacterial alginate lyases.

The extracellular alginate lyases were purified from Vibrio harveyi AL-128 and V. alginolyticus ATCC 17749. The former enzyme appears to be specific for alpha-1,4 bonds involving L-guluronate units in alginate, whereas the latter exhibits specificity for beta-1,4 bonds involving D-mannuronate units. The molecular weights of the enzymes were estimated to be 57,000 and 47,000, and they had isoelectric points of 4.3 and 4.6, respectively. The enzyme from strain AL-128 was most active at NaCl concentrations of 0.3 to 1.0 M. Optimum activity of the enzyme from strain ATCC 17749 was found in the presence of 5 to 10 mM CaCl2.

Alginates↗
PubMed2000

Increased growth of the microalga Chlorella vulgaris when coimmobilized and cocultured in alginate beads with the plant-growth-promoting bacterium Azospirillum brasilense.

Coimmobilization of the freshwater microalga Chlorella vulgaris and the plant-growth-promoting bacterium Azospirillum brasilense in small alginate beads resulted in a significantly increased growth of the microalga. Dry and fresh weight, total number of cells, size of the microalgal clusters (colonies) within the bead, number of microalgal cells per cluster, and the levels of microalgal pigments significantly increased. Light microscopy revealed that both microorganisms colonized the same cavities inside the beads, though the microalgae tended to concentrate in the more aerated periphery while the bacteria colonized the entire bead. The effect of indole-3-acetic acid addition to microalgal culture prior to immobilization of microorganisms in alginate beads partially imitated the effect of A. brasilense. We propose that coimmobilization of microalgae and plant-growth-promoting bacteria is an effective means of increasing microalgal populations within confined environments.

Alginates↗
PubMed1986

Association of alginate from Pseudomonas aeruginosa with two forms of heparin-binding lectin isolated from rat lung.

An endogenous heparin-binding lectin activity isolated from rat lung was separated into two distinct isolectin forms which showed subtle changes in carbohydrate specificity. The two lectin forms displayed different specificities toward alginic acid-purified cystic fibrosis isolates of Pseudomonas aeruginosa when assayed by inhibition of both hemagglutination and [3H]heparin binding. This ability of isolectin forms to show higher affinity toward alginic acid from certain P. aeruginosa strains may suggest that there is a selective mechanism in the colonization of patients with cystic fibrosis.

Alginates↗
PubMed1993

Suppression of lymphocyte and neutrophil functions by Pseudomonas aeruginosa mucoid exopolysaccharide (alginate): reversal by physicochemical, alginase, and specific monoclonal antibody treatments.

The mucoid exopolysaccharide (MEP or alginate) of Pseudomonas aeruginosa is thought to be a virulence factor for this organism by virtue of its ability to suppress local host defense mechanisms. We purified MEP from clinical isolates of mucoid P. aeruginosa, subjected it to degradation by ultrasonication, heat, alkali, and alginase, and reacted it with monoclonal antibodies specific for MEP epitopes. Partial reversal or complete abrogation of the inhibitory effects of alginate on human neutrophil random migration, chemotaxis, and hexose monophosphate shunt activity and lymphocyte transformation were observed following most of these treatments. Physicochemical analysis of degraded MEP revealed a positive correlation between changes in molecular size and viscosity and loss of biological properties. The biological properties of MEP were also shown to be dependent on the structural integrity of the O-acetyl groups substituted for the mannuronic acid residues. The results show that the capacity of MEP to suppress neutrophil and lymphocyte functions is dependent on its acetyl content and the physical properties of large size and viscosity and may provide part of the explanation for the propensity of mucoid P. aeruginosa to persist in the airways of patients with cystic fibrosis. These findings highlight the important role of MEP as one of the virulence factors in the pathogenesis of inflammatory damage and subsequent pulmonary destruction in cystic fibrosis.

Alginates↗
PubMed1995

Biologic activities of antibodies to the neutral-polysaccharide component of the Pseudomonas aeruginosa lipopolysaccharide are blocked by O side chains and mucoid exopolysaccharide (alginate).

Virulent strains of Pseudomonas aeruginosa are either of a nonmucoid, lipopolysaccharide (LPS)-smooth or mucoid, LPS-rough phenotype, and immunity to these different variants is efficiently mediated by antibodies specific to O antigens or mucoid exopolysaccharide (also called alginate), respectively. In addition to O side chains and core polysaccharide components, the LPS of P. aeruginosa also contains neutral-polysaccharide components that express antigenic determinants common to many clinical isolates. We evaluated antibodies specific to neutral polysaccharides for the ability to mediate opsonic killing and protective immunity. Antibodies to these antigens mediated opsonic killing of poorly virulent nonmucoid LPS-rough isolates but not of isogenic strains with either a LPS-smooth or a mucoid phenotype. Antibodies to neutral-polysaccharide antigens also failed to protect neutropenic mice from challenge with modest doses of LPS-smooth P. aeruginosa strains (< 10(3) CFU per mouse), whereas O-antigen-specific antibodies were highly protective. Antibodies to neutral polysaccharides deposited significantly (P = 0.002) more C3 onto LPS-rough strains than did antibodies to O side chains, but this situation was reversed when isogenic LPS-smooth strains were tested. Given that protective immunity against P. aeruginosa must be directed against either nonmucoid LPS-smooth strains or mucoid LPS-rough strains, it appears that antibodies specific to neutral-polysaccharide antigens do not protect against P. aeruginosa infection. Lack of protection is likely due to the ability of both O side chains and mucoid exopolysaccharide (alginate) to interfere with the opsonic killing activity of neutral-polysaccharide-specific antibodies.

Alginates↗
PubMed2003

Construction and characterization of a Pseudomonas aeruginosa mucoid exopolysaccharide-alginate conjugate vaccine.

Deterioration of lung function in patients with cystic fibrosis (CF) is closely associated with chronic pulmonary infection with mucoid Pseudomonas aeruginosa. The mucoid exopolysaccharide (MEP) from P. aeruginosa has been shown to induce opsonic antibodies in mice that are protective against this chronic infection. MEP-specific opsonic antibodies are also commonly found in the sera of older CF patients lacking detectable P. aeruginosa infection. When used in a human vaccine trial, however, MEP only minimally induced opsonic antibodies. To evaluate whether conjugation of MEP to a carrier protein could improve its immunogenicity, we bound thiolated MEP to keyhole limpet hemocyanin (KLH) by using succinimidyl-4-(N-maleimidomethyl)cyclohexane-1-carboxylate (SMCC) as a linker. In contrast to the native MEP polymer, the MEP-KLH conjugate vaccine induced high titers of MEP-specific immunoglobulin G (IgG) in C3H-HeN mice and in a rabbit. Sera from mice immunized with MEP-KLH conjugate, but not from animals immunized with comparable doses of native MEP, demonstrated opsonic killing activity. Vaccination with MEP-KLH conjugate induced opsonic antibodies broadly cross-reactive to heterologous mucoid strains of P. aeruginosa. Preexisting nonopsonic antibodies to MEP are found in normal human sera, including young CF patients, and their presence impedes the induction of opsonic antibodies. Induction of nonopsonic antibodies by either intraperitoneal injection of MEP or injection or feeding of the cross-reactive antigen, seaweed alginate, reduced the level of overall IgG elicited by follow-up immunization with the MEP-KLH conjugate. However, the opsonic activity was lower only in the sera of MEP-KLH conjugate-immunized mice with preexisting antibodies induced by MEP but not with antibodies induced by seaweed alginate. Immunization with MEP-KLH elicited a significant proportion of antibodies specific to epitopes involving O-acetate residues, and this subpopulation of antibodies mediated opsonic killing of mucoid P. aeruginosa in vitro. These results indicate that conjugation of MEP to KLH significantly enhances its immunogenicity and the elicitation of opsonic antibodies in mice and rabbits, that the conjugate induces opsonic antibodies in the presence of preexisting nonopsonic antibodies, and that opsonic antibodies to MEP are directed at epitopes that include acetate residues on the uronic acid polymer.

Alginates↗
PubMed1985

Fructose 1,6-bisphosphate aldolase activity is essential for synthesis of alginate from glucose by Pseudomonas aeruginosa.

We have isolated a mutant of Pseudomonas aeruginosa deficient in fructose 1,6-bisphosphate aldolase activity. This mutant, similar to the mutants deficient in any of the Entner-Doudoroff pathway enzymes, does not allow appreciable alginate formation from glucose and gluconate, but allows alginate synthesis from mannitol and fructose. This suggests that glucose and gluconate must be converted to fructose 1,6-bisphosphate via the Entner-Doudoroff pathway enzymes and fructose 1,6-bisphosphate aldolase.

Alginates↗
PubMed1985

Clustering of mutations affecting alginic acid biosynthesis in mucoid Pseudomonas aeruginosa.

A 10-kilobase DNA fragment previously shown to contain the phosphomannose isomerase gene (pmi) of Pseudomonas aeruginosa was used to construct a pBR325-based hybrid that can be propagated in P. aeruginosa only by the formation of a chromosomal-plasmid cointegrate. This plasmid, designated pAD4008, was inserted into the P. aeruginosa chromosome by recombination at a site of homology between the cloned P. aeruginosa DNA and the chromosome. Mobilization of pAD4008 into P. aeruginosa PAO and 8830 and selection for the stable acquisition of tetracycline resistance resulted in specific and predictable changes in the pattern of endonuclease restriction sites in the phosphomannose isomerase gene region of the chromosomes. Chromosomal DNA from the tetracycline-resistant transformants was used to clone the drug resistance determinant with Bg/II or XbaI, thereby allowing the "walking" of the P. aeruginosa chromosome in the vicinity of the pmi gene. Analysis of overlapping tetracycline-resistant clones indicated the presence of sequences homologous to the DNA insert of plasmid pAD2, a recombinant clone of P. aeruginosa origin previously shown to complement several alginate-negative mutants. Restriction mapping, subcloning, and complementation analysis of a 30-kilobase DNA region demonstrated the tight clustering of several genetic loci involved in alginate biosynthesis. Furthermore, the tetracycline resistance determinant in PAO strain transformed by pAD4008 was mapped on the chromosome by plasmid FP2-mediated conjugation and was found to be located near 45 min.

Alginates↗
PubMed1994

Gene cluster controlling conversion to alginate-overproducing phenotype in Pseudomonas aeruginosa: functional analysis in a heterologous host and role in the instability of mucoidy.

Conversion to mucoidy, caused by the overproduction of the exopolysaccharide alginate in laboratory and cystic fibrosis strains of Pseudomonas aeruginosa, can occur via frameshift or nonsense mutations in the second gene of the algU mucA mucB cluster. The first gene of the cluster, algU, encodes a putative alternative sigma factor required for algD transcription. The algD gene encodes a critical alginate biosynthetic enzyme and is invariably activated in mucoid P. aeruginosa cells. To investigate the function of the genes controlling conversion to mucoidy, the wild-type algU mucA mucB cluster from the standard genetic strain PAO1 was used to reconstitute algD transcription in Escherichia coli. Transcription of an algD-lacZ chromosomal fusion in E. coli was detected upon introduction of plasmid-borne algU mucA mucB. Moreover, insertional inactivation of either mucA or mucB resulted in further stimulation of transcriptional activity from the algD promoter. This activation was dependent on algU, since a double algU mucA mutation abrogated transcription of algD. These experiments suggest that the phenotypic manifestations of muc mutations, i.e., increased algD expression and mucoid phenotype, depend on the presence of an active algU gene and that this regulator and the factors encoded by the downstream genes interact. Further support for these conclusions came from the investigations of the mechanism of reversion to nonmucoidy in P. aeruginosa, a phenomenon frequently referred to as the instability of mucoid phenotype. Spontaneous nonmucoid derivatives of the mucoid strain PAO578 carrying the mucA22 mutation were examined for the presence of alterations within the algU mucA mucB locus. Point mutations which inactivated algU were detected in some, but not all, nonmucoid revertants. No reversion of the original mucA22 mutation (a deletion of one C) was observed in any of the investigated strains. This observation suggests that the process of conversion to nonmucoidy ban be explained, at least partially, by second-site suppressor mutations and that a fraction of such mutations occurs in algU.

Alginates↗
PubMed1994

Purification and characterization of phosphomannomutase/phosphoglucomutase from Pseudomonas aeruginosa involved in biosynthesis of both alginate and lipopolysaccharide.

The algC gene from Pseudomonas aeruginosa has been shown to encode phosphomannomutase (PMM), an essential enzyme for biosynthesis of alginate and lipopolysaccharide (LPS). This gene was overexpressed under control of the tac promoter, and the enzyme was purified and its substrate specificity and metal ion effects were characterized. The enzyme was determined to be a monomer with a molecular mass of 50 kDa. The enzyme catalyzed the interconversion of mannose 1-phosphate (M1P) and mannose 6-phosphate, as well as that of glucose 1-phosphate (G1P) and glucose 6-phosphate. The apparent Km values for M1P and G1P were 17 and 22 microM, respectively. On the basis of Kcat/Km ratio, the catalytic efficiency for G1P was about twofold higher than that for M1P. PMM also catalyzed the conversion of ribose 1-phosphate and 2-deoxyglucose 6-phosphate to their corresponding isomers, although activities were much lower. Purified PMM/phosphoglucomutase (PGM) required Mg2+ for maximum activity; Mn2+ was the only other divalent metal that showed some activation. The presence of other divalent metals in addition to Mg2+ in the reaction inhibited the enzymatic activity. PMM and PGM activities could not be detected in nonmucoid algC mutant strain 8858 and in LPS-rough algC mutant strain AK1012, while they were present in the wild-type strains as well as in algC-complemented mutant strains. This evidence suggests that AlgC functions as PMM and PGM in vivo, converting phosphomannose and phosphoglucose in the biosynthesis of both alginate and LPS.

Alginates↗
PubMed1996

Characterization of the genes coding for the putative sigma factor AlgU and its regulators MucA, MucB, MucC, and MucD in Azotobacter vinelandii and evaluation of their roles in alginate biosynthesis.

The study of the biosynthesis of alginate, the exopolysaccharide produced by Azotobacter vinelandii and Pseudomonas aeruginosa, has biotechnological and medical significance. We report here the identification of the A. vinelandii genes coding for the putative sigma factor AlgU and its negative regulators MucA and MucB through the suppression of the highly mucoid phenotype of an A. vinelandii strain by a plasmid encoding MucA and MucB. The sequences of the A. vinelandii algU, mucA, and mucB genes are highly homologous to those of the corresponding P. aeruginosa genes, AlgU shows 93% identity, and MucA and MucB are 64.4 and 63.9% identical, respectively. Forming part of the same operon as algU, mucA, and mucB, two additional genes (mucC and mucD) were identified and sequenced; the product of the former gene is homologous to ORF4 of Photobacterium sp. strain SS9, and that of the latter gene belongs to the HtrA serine protease family. Interestingly, the nonmucoid A. vinelandii UW136 had a 0.9-kb insertion within the algU gene. A strong correlation between AlgU activity and alginate production by A. vinelandii was also found, as reflected in the level of algD transcription.

Alginates↗