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1.
Int Microbiol ; 24(3): 441-453, 2021 Aug.
Artículo en Inglés | MEDLINE | ID: mdl-33987705

RESUMEN

Globally, the underlying peril of cumulative toxicity of heavy metals in water bodies contaminated by industrial effluents is a matter of great concern to the environmentalists. Heavy metals like lead, cadmium, and nickel are particularly liable for this. Such toxic water is not only hazardous to human health but also harmful to aquatic animals. Remedial measures are being taken by physico-chemical techniques, but most of them are neither eco-friendly nor cost-effective. Biological means like bioaccumulation of heavy metals by viable bacteria are often tedious. In the present study, biosorption of heavy metals is successfully expedited by surfactant exopolysaccharide (SEPS) of Ochrobactrum pseudintermedium C1 as a simple, safe, and economically sustainable option utilizing an easily available and cost-effective substrate like molasses extract. Its efficacy in bioremediation of toxic heavy metals like cadmium, nickel, and lead have been studied by UV-Vis spectrophotometry and verified by inductively coupled plasma-atomic emission spectroscopy (ICP-AES). FTIR and zeta potential studies have also been carried out to explore this novel biosorption potential. Results are conclusive and promising. Moreover, this particular SEPS alone can remediate all these three toxic heavy metals in water. For futuristic applications, it might be a prospective and cost-effective resource for bioremediation of toxic heavy metals in aqueous environment.


Asunto(s)
Metales Pesados/metabolismo , Ochrobactrum/metabolismo , Polisacáridos Bacterianos/metabolismo , Tensoactivos/metabolismo , Contaminantes Químicos del Agua/metabolismo , Biodegradación Ambiental , Cadmio/metabolismo , Análisis Costo-Beneficio , Plomo/metabolismo , Microscopía Electrónica de Rastreo , Níquel/metabolismo , Polisacáridos Bacterianos/ultraestructura
2.
Cell Mol Biol (Noisy-le-grand) ; 67(1): 89-95, 2021 Jan 31.
Artículo en Inglés | MEDLINE | ID: mdl-34817363

RESUMEN

Periodontal pain is a public health problem derived from different conditions, including periodontal diseases, prosthetic complications, and even extractions performed by dentist. There are various treatments to control acute dental pain, being the administration of analgesics, such as Lysine Clonixinate (LC), a common practice. Unfortunately, higher and repeated dosages are usually required. The purpose of this work was to develop a prolonged release pharmaceutical form as an alternative treatment for dental pain. Hence, we conceived a film based on guar gum and loaded different concentrations of LC. We evaluated the film's appearance, brittleness, strength, and flexibility, and then chose one formulation for adequate characteristics. Subsequently, we assessed the morphology, thermal behavior, and swelling properties of the films (LC-free and -loaded). Finally, we performed the release studies of LC from the films in vitro using a simulated saliva medium and employed several mathematical models to evaluate the release kinetics. Guar gum is a natural polymer obtained from the endosperm of Cyamopsis tetragonolobus that presents properties such as biosafety, biocompatibility, and biodegradability. Thus, it represents a potential excipient for use in pharmaceutical formulations. Moreover, our results revealed that the LC-loaded film presented a high adherence, suitable swelling behavior, high LC content, and a prolonged drug release. Therefore, the LC-loaded film may be considered a potential option to be applied as an alternative to treat dental pain.


Asunto(s)
Clonixina/análogos & derivados , Lisina/análogos & derivados , Dolor/tratamiento farmacológico , Enfermedades Periodontales/tratamiento farmacológico , Polisacáridos Bacterianos/química , Analgésicos/farmacocinética , Analgésicos/uso terapéutico , Clonixina/farmacocinética , Clonixina/uso terapéutico , Liberación de Fármacos , Excipientes/química , Humanos , Cinética , Lisina/farmacocinética , Lisina/uso terapéutico , Membranas Artificiales , Microscopía Electrónica de Rastreo , Dolor/complicaciones , Enfermedades Periodontales/complicaciones , Polímeros/química , Polisacáridos Bacterianos/ultraestructura , Temperatura , Termogravimetría/métodos
3.
Cell Mol Biol (Noisy-le-grand) ; 67(1): 80-88, 2021 Jan 31.
Artículo en Inglés | MEDLINE | ID: mdl-34817364

RESUMEN

Bacterial vaginosis is a vaginal infection that affects 60% of women of reproductive age worldwide. It is mainly caused by the bacterium Gardnerella vaginalis and is a factor that increases the probability of getting sexually transmitted diseases. We aimed to develop a new pharmaceutical form for the treatment of vaginal infections. We employed the solving-casting method to fabricate a polymeric film with Xanthan gum, a natural polymer produced by the bacterium Xanthomonas campestris, and metronidazole, one of the most commonly used drugs for vaginal infections. In order to characterize the film, we measured pH, dose uniformity, dissolution profile, and the percentage of swelling. Moreover, we performed a thermogravimetric analysis and scanning electron microscopy. The results demonstrated a pH suitable for vaginal application and uniform distribution of the drug in the film. Also, the formulation exhibited a high percentage of swelling and a slow release of the drug in a simulated vaginal fluid medium. All these attributes indicated that the manufactured film has ideal characteristics to be used and administered vaginally. It could be an excellent alternative to treat bacterial vaginosis and also improve user adherence.


Asunto(s)
Gardnerella vaginalis/efectos de los fármacos , Metronidazol/uso terapéutico , Polisacáridos Bacterianos/química , Vagina/efectos de los fármacos , Vaginosis Bacteriana/tratamiento farmacológico , Antibacterianos/administración & dosificación , Antibacterianos/farmacocinética , Antibacterianos/uso terapéutico , Liberación de Fármacos , Femenino , Gardnerella vaginalis/fisiología , Humanos , Concentración de Iones de Hidrógeno , Membranas Artificiales , Metronidazol/administración & dosificación , Metronidazol/farmacocinética , Microscopía Electrónica de Rastreo , Polímeros/química , Polisacáridos Bacterianos/ultraestructura , Temperatura , Termogravimetría/métodos , Resultado del Tratamiento , Vagina/microbiología , Vaginosis Bacteriana/microbiología
4.
Drug Discov Today Technol ; 35-36: 23-33, 2020 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-33388125

RESUMEN

Microbial surface polysaccharides are important virulence factors and targets for vaccine development. Glycoconjugate vaccines, obtained by covalently linking carbohydrates and proteins, are well established tools for prevention of bacterial infections. Elucidation of the minimal portion involved in the interactions with functional antibodies is of utmost importance for the understanding of their mechanism of induction of protective immune responses and the design of synthetic glycan based vaccines. Typically, this is achieved by combination of different techniques, which include ELISA, glycoarray, Surface Plasmon Resonance in conjunction with approaches for mapping at atomic level the position involved in binding, such as Saturation Transfer NMR and X-ray crystallography. This review provides an overview of the structural studies performed to map glycan epitopes (glycotopes), with focus on the highly complex structure of Group B Streptococcus type III (GBSIII) capsular polysaccharide. Furthermore, it describes the rational process followed to translate the obtained information into the design of a protective glycoconjugate vaccine based on a well-defined synthetic glycan epitope.


Asunto(s)
Polisacáridos Bacterianos/administración & dosificación , Infecciones Estreptocócicas/prevención & control , Vacunas Estreptocócicas/administración & dosificación , Streptococcus agalactiae/inmunología , Animales , Cristalografía por Rayos X , Modelos Animales de Enfermedad , Diseño de Fármacos , Epítopos/administración & dosificación , Epítopos/inmunología , Epítopos/ultraestructura , Glicoconjugados/administración & dosificación , Glicoconjugados/química , Glicoconjugados/inmunología , Humanos , Inmunogenicidad Vacunal , Polisacáridos Bacterianos/inmunología , Polisacáridos Bacterianos/ultraestructura , Infecciones Estreptocócicas/inmunología , Infecciones Estreptocócicas/microbiología , Vacunas Estreptocócicas/síntesis química , Vacunas Estreptocócicas/inmunología , Relación Estructura-Actividad , Vacunas Sintéticas/administración & dosificación , Vacunas Sintéticas/química , Vacunas Sintéticas/inmunología
5.
Molecules ; 26(1)2020 Dec 24.
Artículo en Inglés | MEDLINE | ID: mdl-33374301

RESUMEN

Bacterial cellulose (BC) is a natural polymer that has fascinating attributes, such as biocompatibility, low cost, and ease of processing, being considered a very interesting biomaterial due to its options for moldability and combination. Thus, BC-based compounds (for example, BC/collagen, BC/gelatin, BC/fibroin, BC/chitosan, etc.) have improved properties and/or functionality, allowing for various biomedical applications, such as artificial blood vessels and microvessels, artificial skin, and wounds dressing among others. Despite the wide applicability in biomedicine and tissue engineering, there is a lack of updated scientific reports on applications related to dentistry, since BC has great potential for this. It has been used mainly in the regeneration of periodontal tissue, surgical dressings, intraoral wounds, and also in the regeneration of pulp tissue. This review describes the properties and advantages of some BC studies focused on dental and oral applications, including the design of implants, scaffolds, and wound-dressing materials, as well as carriers for drug delivery in dentistry. Aligned to the current trends and biotechnology evolutions, BC-based nanocomposites offer a great field to be explored and other novel features can be expected in relation to oral and bone tissue repair in the near future.


Asunto(s)
Bacterias/química , Materiales Biocompatibles/química , Celulosa/química , Odontología , Celulosa/ultraestructura , Odontología/métodos , Polisacáridos Bacterianos/química , Polisacáridos Bacterianos/ultraestructura
6.
Biomacromolecules ; 20(4): 1731-1739, 2019 04 08.
Artículo en Inglés | MEDLINE | ID: mdl-30816699

RESUMEN

Polysaccharides are ubiquitous in nature and represent an essential class of biopolymers with multiple levels of conformation and structural hierarchy. However, a standardized structural nomenclature, as in the case of proteins, is still lacking due to uncertainty on their hierarchical organization. In this work we use carrageenans as model polysaccharides to demonstrate that several structural levels exist and can be unambiguously resolved by statistical analysis on high resolution Atomic Force Microscopy images, supported by spectroscopic, X-ray scattering and rheological techniques. In direct analogy with proteins, we identify primary, secondary, tertiary and quaternary structures. The structure-property relationship induced by monovalent ions for κ-, ι- and the non-gelling control λ-carrageenan is established from the single chain regime to the occurrence of hydrogels at higher concentrations. For κ-carrageenan in the presence of potassium, a disorder-order transition from random coil to single helix is first observed (secondary structure), followed by intrachain supercoiling events (tertiary structure) and macroscopic anisotropic domains which are parts of a network (quaternary structure) with tunable elasticity up to ∼103 Pa. In contrast, κ-carrageenan in the presence of sodium only produces changes in secondary structure without supercoiling events, prior to formation of gels, highlighting the ion-specificity of the process. Loosely intertwined single helices are observed for ι-carrageenan in the presence of sodium and potassium chloride, providing an elastic mesh with many junction zones, while λ-carrageenan does not undergo any structural change. A generality of the observed behavior may be inferred by extending these observations to a distinct class of polysaccharides, the weak carboxylic polyelectrolyte Gellan gum. These results advance our understanding of ion-specific structural changes of polysaccharides and the physical mechanisms responsible for their gelation.


Asunto(s)
Carragenina/química , Hidrogeles/química , Microscopía de Fuerza Atómica , Polisacáridos Bacterianos/química , Conformación de Carbohidratos , Carragenina/ultraestructura , Polisacáridos Bacterianos/ultraestructura
7.
Curr Microbiol ; 76(3): 355-360, 2019 Mar.
Artículo en Inglés | MEDLINE | ID: mdl-30684027

RESUMEN

The secretomes of the strain Cellulosimicrobium cellulans F16 grown on different carbon sources were analyzed by zymography, and the subcellular surface structures were extensively studied by electron microscope. The exo-cellulase and xylanase systems were sparse when cells were grown on soluble oligosaccharides, but were significantly increased when grown on complex and water-insoluble polysaccharides, such as Avicel, corn cob, and birchwood xylan. The cellulosome-like protuberant structures were clearly observed on the cell surfaces of strain F16 grown on cellulose, with diameters of 15-20 nm. Fibrous structures that connected the adjacent cells can be seen under microscope. Moreover, protuberances that adsorbed the cell to cellulose were also observed. As the adhesion of Cellulosimicrobium cellulans cells onto cellulose surfaces occurs via thick bacterial curdlan-type exopolysaccharides (EPS), such surface layer is potentially important in the digestion of insoluble substrates such as cellulose or hemicellulose, and the previously reported xylanosomes are part of such complex glycocalyx layer on the surface of the bacterial cell.


Asunto(s)
Actinobacteria/enzimología , Actinobacteria/ultraestructura , Carbono/metabolismo , Actinobacteria/metabolismo , Adhesión Bacteriana , Celulosa/metabolismo , Celulosomas/ultraestructura , Glicocálix/ultraestructura , Polisacáridos Bacterianos/metabolismo , Polisacáridos Bacterianos/ultraestructura , Xilosidasas/metabolismo , beta-Glucanos/metabolismo , beta-Glucosidasa/metabolismo
8.
J Basic Microbiol ; 59(8): 820-833, 2019 Aug.
Artículo en Inglés | MEDLINE | ID: mdl-31232462

RESUMEN

During production and characterization of exopolysaccharides (EPS) of Ochrobactrum pseudintermedium C1, it was observed that an experimental change in the basic hydrocarbon type of substrate for bacterial utilization led to elicitation of different surface-active properties in the EPS produced. In the sugar substrate, it elicited surfactant property, while in oil substrates it elicited emulsifying property, which indicated that the EPS might be different. Consequently, attention was focused on a detailed analysis of this substrate-specific EPS. Utilizing waste sugar, edible, and mineral oil substrates, EPS produced in each situation was characterized. Besides estimating surface activity and thermostability, each substrate-specific EPS was analyzed by Fourier-transform infrared spectroscopy, gas chromatography-mass spectroscopy, 1 H-nuclear magnetic resonance, and matrix-assisted laser desorption/ionization-time of flight mass spectroscopy to find any structural difference. The results were significantly contrasting although the similarity in molecular mass suggested a basic similarity in polysaccharide structure. Morphological differences were also evident both macroscopically and microscopically with scanning electron microscopy. As the surface-active property of EPS was dependent on the substrate utilized, their structural differences might account for it. These diverse surface activities of EPS produced by a single bacterial strain simply by changing the nature of substrate would also augment their bioapplications. Moreover, utilization of waste and easily available substrates should make such applications convenient, ecofriendly, and cost-worthy.


Asunto(s)
Hidrocarburos/metabolismo , Ochrobactrum/química , Polisacáridos Bacterianos/química , Medios de Cultivo/metabolismo , Microscopía Electrónica de Rastreo , Peso Molecular , Ochrobactrum/crecimiento & desarrollo , Ochrobactrum/metabolismo , Polisacáridos Bacterianos/biosíntesis , Polisacáridos Bacterianos/ultraestructura , Solubilidad , Propiedades de Superficie , Temperatura
9.
Phytopathology ; 107(4): 403-411, 2017 04.
Artículo en Inglés | MEDLINE | ID: mdl-28045342

RESUMEN

Fire blight, caused by the pathogen Erwinia amylovora, is the most devastating bacterial disease of pome fruit in North America and worldwide. The primary method of dispersal for E. amylovora is through ooze, a mass of exopolysaccharides and bacterial cells that is exuded as droplets from infected host tissue. During the 2013 and 2014 field seasons, 317 ooze droplets were collected from field-inoculated apple trees. Populations of E. amylovora in ooze droplets were 108 CFU/µl on average. Ooze droplets harboring larger (>108 CFU/µl) cell populations were typically smaller in total volume and had darker coloring, such as orange, red, or dark red hues. Examination of apple host tissue at the site of emergence of ooze droplets using scanning electron microscopy revealed that ooze was not exuding through natural openings; instead, it was found on erumpent mounds and small (10-µm) tears in tissue. These observations suggested that E. amylovora-induced wounds in tissue provided the exit holes for ooze extrusion from the host. Analyses of E. amylovora populations in ooze droplets and within the stems from which ooze droplets emerged indicated that approximately 9% of the total bacterial population from infected stems is diverted to ooze. Gene expression analyses indicated that E. amylovora cells in stem sections located above ooze droplets and in ooze droplets were actively expressing critical pathogenicity genes such as hrpL, dspE, and amsK. Thus, our study identified ooze as a source of large, concentrated populations of E. amylovora that emerged from the host by rupturing host tissue. Because the cells in ooze droplets are expressing genes required for pathogenesis, they are already primed for infection should they be dispersed from ooze to new infection courts.


Asunto(s)
Erwinia amylovora/aislamiento & purificación , Malus/microbiología , Enfermedades de las Plantas/microbiología , Polisacáridos Bacterianos/metabolismo , Proteínas Bacterianas/genética , Proteínas Bacterianas/metabolismo , Erwinia amylovora/genética , Erwinia amylovora/metabolismo , Erwinia amylovora/patogenicidad , Flores/microbiología , Frutas/microbiología , Regulación Bacteriana de la Expresión Génica , Microscopía Electrónica de Rastreo , Tallos de la Planta/microbiología , Polisacáridos Bacterianos/ultraestructura , Virulencia
10.
J Dairy Sci ; 100(9): 6895-6905, 2017 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-28711240

RESUMEN

Exopolysaccharide (EPS) was extracted and purified from Lactobacillus plantarum WLPL04, which has been confirmed previously as a potential probiotic for its antagonistic and immune-modulating activity. It has a molecular weight of 6.61 × 104 Da, consisting of xylose, glucose, and galactose in an approximate molar ratio of 3.4:1.8:1. Microstructural studies demonstrated that the EPS appeared as a smooth sheet structure with many homogeneous rod-shaped lumps. The preliminary in vitro assays indicated that the EPS could significantly inhibit the adhesion of Escherichia coli O157:H7 to HT-29 cells in competition, replacement, and inhibition assays at a dose of 1.0 mg/mL, with an inhibition rate of 20.24 ± 2.23, 29.71 ± 1.21, and 30.57 ± 1.73%, respectively. Additionally, the EPS exhibited strong inhibition against biofilm formation by pathogenic bacteria, including Pseudomonas aeruginosa CMCC10104, E. coli O157:H7, Salmonella Typhimurium ATCC13311, and Staphylococcus aureus CMCC26003. Furthermore, the EPS showed good inhibitory activity against the proliferation of HT-29 cells. The characteristics and bioactivities of this EPS may make it a promising candidate in developing functional food.


Asunto(s)
Lactobacillus plantarum/química , Polisacáridos Bacterianos/aislamiento & purificación , Probióticos/química , Animales , Adhesión Bacteriana/efectos de los fármacos , Escherichia coli O157 , Células HT29 , Humanos , Peso Molecular , Polisacáridos Bacterianos/química , Polisacáridos Bacterianos/farmacología , Polisacáridos Bacterianos/ultraestructura , Salmonella typhimurium/efectos de los fármacos , Staphylococcus aureus/efectos de los fármacos
11.
Mol Microbiol ; 96(4): 728-43, 2015 May.
Artículo en Inglés | MEDLINE | ID: mdl-25662512

RESUMEN

Elevated levels of the second messenger c-di-GMP activate biosynthesis of an unknown exopolysaccharide (EPS) in the food-borne pathogen Listeria monocytogenes. This EPS strongly protects cells against disinfectants and desiccation, indicating its potential significance for listerial persistence in the environment and for food safety. We analyzed the potential phylogenetic origin of this EPS, determined its complete structure, characterized genes involved in its biosynthesis and hydrolysis and identified diguanylate cyclases activating its synthesis. Phylogenetic analysis of EPS biosynthesis proteins suggests that they have evolved within monoderms. Scanning electron microscopy revealed that L. monocytogenes EPS is cell surface-bound. Secreted carbohydrates represent exclusively cell-wall debris. Based on carbohydrate composition, linkage and NMR analysis, the structure of the purified EPS is identified as a ß-1,4-linked N-acetylmannosamine chain decorated with terminal α-1,6-linked galactose. All genes of the pssA-E operon are required for EPS production and so is a separately located pssZ gene. We show that PssZ has an EPS-specific glycosylhydrolase activity. Exogenously added PssZ prevents EPS-mediated cell aggregation and disperses preformed aggregates, whereas an E72Q mutant in the presumed catalytic residue is much less active. The diguanylate cyclases DgcA and DgcB, whose genes are located next to pssZ, are primarily responsible for c-di-GMP-dependent EPS production.


Asunto(s)
GMP Cíclico/análogos & derivados , Listeria monocytogenes/genética , Listeria monocytogenes/metabolismo , Polisacáridos Bacterianos/biosíntesis , Polisacáridos Bacterianos/química , Proteínas Bacterianas/genética , Proteínas Bacterianas/metabolismo , GMP Cíclico/genética , GMP Cíclico/metabolismo , Proteínas de Escherichia coli/genética , Proteínas de Escherichia coli/metabolismo , Glicosiltransferasas/genética , Hexosaminas/análisis , Listeria monocytogenes/química , Listeria monocytogenes/ultraestructura , Microscopía Electrónica de Rastreo , Operón , Liasas de Fósforo-Oxígeno/genética , Liasas de Fósforo-Oxígeno/metabolismo , Filogenia , Polisacáridos Bacterianos/genética , Polisacáridos Bacterianos/ultraestructura
12.
Arch Microbiol ; 198(2): 205-9, 2016 Mar.
Artículo en Inglés | MEDLINE | ID: mdl-26581416

RESUMEN

An exopolysaccharide (EPS)-producing heavy metal-resistant Gram-negative bacterium was isolated from ore-contaminated soil. The selected strain was identified by 16S rDNA sequencing and designated as Halomonas sp. MG. Phylogenetic analysis of the gene sequence showed its close similarity with Halomonas sp. Field emission scanning electron microscopy analysis revealed that the EPS had a porous structure with small pores. X-ray diffractograms showed the non-crystalline nature of the EPS. Further, FTIR spectroscopic analysis revealed the presence of carboxyl, hydroxyl and amide groups corresponding to a typical EPS.


Asunto(s)
Halomonas/clasificación , Halomonas/aislamiento & purificación , Polisacáridos Bacterianos/metabolismo , Halomonas/efectos de los fármacos , Halomonas/metabolismo , Metales Pesados/toxicidad , Microscopía Electrónica de Rastreo , Filogenia , Polisacáridos Bacterianos/ultraestructura , ARN Ribosómico 16S/genética , Especificidad de la Especie
13.
Biodegradation ; 23(5): 775-83, 2012 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-22544353

RESUMEN

A lead resistant bacterial strain isolated from effluent of lead battery manufacturing company of Goa, India has been identified as Enterobacter cloacae strain P2B based on morphological, biochemical characters, FAME profile and 16S rDNA sequence data. This bacterial strain could resist lead nitrate up to 1.6 mM. Significant increase in exopolysaccharide (EPS) production was observed as the production increased from 28 to 108 mg/L dry weight when exposed to 1.6 mM lead nitrate in Tris buffered minimal medium. Fourier-transformed infrared spectroscopy of this EPS revealed presence of several functional groups involved in metal binding viz. carboxyl, hydroxyl and amide groups along with glucuronic acid. Gas chromatography coupled with mass spectrometry analysis of alditol-acetate derivatives of acid hydrolysed EPS produced in presence of 1.6 mM lead nitrate demonstrated presence of several neutral sugars such as rhamnose, arabinose, xylose, mannose, galactose and glucose, which contribute to lead binding hydroxyl groups. Scanning electron microscope coupled with energy dispersive X-ray spectrometric analysis of this lead resistant strain exposed to 1.6 mM lead nitrate interestingly revealed mucous EPS surrounding bacterial cells which sequestered 17 % lead (as weight %) extracellularly and protected the bacterial cells from toxic effects of lead. This lead resistant strain also showed multidrug resistance. Thus these results significantly contribute to better understanding of structure, function and environmental application of lead-enhanced EPSs produced by bacteria. This lead-enhanced biopolymer can play a very important role in bioremediation of several heavy metals including lead.


Asunto(s)
Enterobacter cloacae/efectos de los fármacos , Enterobacter cloacae/metabolismo , Plomo/toxicidad , Polisacáridos Bacterianos/biosíntesis , Biodegradación Ambiental/efectos de los fármacos , Enterobacter cloacae/crecimiento & desarrollo , Enterobacter cloacae/ultraestructura , Cromatografía de Gases y Espectrometría de Masas , India , Polisacáridos Bacterianos/ultraestructura , Espectrometría por Rayos X , Espectroscopía Infrarroja por Transformada de Fourier
14.
J Biol Chem ; 285(14): 10464-71, 2010 Apr 02.
Artículo en Inglés | MEDLINE | ID: mdl-20106971

RESUMEN

In Gram-positive bacteria, the functional role of surface polysaccharides (PS) that are not of capsular nature remains poorly understood. Here, we report the presence of a novel cell wall PS pellicle on the surface of Lactococcus lactis. Spontaneous PS-negative mutants were selected using semi-liquid growth conditions, and all mutations were mapped in a single chromosomal locus coding for PS biosynthesis. PS molecules were shown to be composed of hexasaccharide phosphate repeating units that are distinct from other bacterial PS. Using complementary atomic force and transmission electron microscopy techniques, we showed that the PS layer forms an outer pellicle surrounding the cell. Notably, we found that this cell wall layer confers a protective barrier against host phagocytosis by murine macrophages. Altogether, our results suggest that the PS pellicle could represent a new cell envelope structural component of Gram-positive bacteria.


Asunto(s)
Cápsulas Bacterianas/química , Pared Celular/química , Lactococcus lactis/metabolismo , Macrófagos/metabolismo , Fagocitosis/fisiología , Polisacáridos Bacterianos/química , Polisacáridos Bacterianos/metabolismo , Adhesión Bacteriana , Proteínas Bacterianas/química , Proteínas Bacterianas/genética , Proteínas Bacterianas/metabolismo , Secuencia de Carbohidratos , Células Cultivadas , Cromosomas Bacterianos , Macrófagos/microbiología , Microscopía de Fuerza Atómica , Microscopía Electrónica de Rastreo , Datos de Secuencia Molecular , Mutagénesis Sitio-Dirigida , Mutación/genética , Polisacáridos Bacterianos/ultraestructura
15.
PLoS Pathog ; 5(3): e1000354, 2009 Mar.
Artículo en Inglés | MEDLINE | ID: mdl-19325879

RESUMEN

Virtually all cells living in multicellular structures such as tissues and organs are encased in an extracellular matrix. One of the most important features of a biofilm is the extracellular polymeric substance that functions as a matrix, holding bacterial cells together. Yet very little is known about how the matrix forms or how matrix components encase bacteria during biofilm development. Pseudomonas aeruginosa forms environmentally and clinically relevant biofilms and is a paradigm organism for the study of biofilms. The extracellular polymeric substance of P. aeruginosa biofilms is an ill-defined mix of polysaccharides, nucleic acids, and proteins. Here, we directly visualize the product of the polysaccharide synthesis locus (Psl exopolysaccharide) at different stages of biofilm development. During attachment, Psl is anchored on the cell surface in a helical pattern. This promotes cell-cell interactions and assembly of a matrix, which holds bacteria in the biofilm and on the surface. Chemical dissociation of Psl from the bacterial surface disrupted the Psl matrix as well as the biofilm structure. During biofilm maturation, Psl accumulates on the periphery of 3-D-structured microcolonies, resulting in a Psl matrix-free cavity in the microcolony center. At the dispersion stage, swimming cells appear in this matrix cavity. Dead cells and extracellular DNA (eDNA) are also concentrated in the Psl matrix-free area. Deletion of genes that control cell death and autolysis affects the formation of the matrix cavity and microcolony dispersion. These data provide a mechanism for how P. aeruginosa builds a matrix and subsequently a cavity to free a portion of cells for seeding dispersal. Direct visualization reveals that Psl is a key scaffolding matrix component and opens up avenues for therapeutics of biofilm-related complications.


Asunto(s)
Biopelículas/crecimiento & desarrollo , Matriz Extracelular/ultraestructura , Polisacáridos Bacterianos/ultraestructura , Pseudomonas aeruginosa/fisiología , ADN Bacteriano , Matriz Extracelular/química , Matriz Extracelular/metabolismo , Genes Bacterianos , Microscopía Confocal , Polisacáridos Bacterianos/química , Polisacáridos Bacterianos/metabolismo
16.
Carbohydr Polym ; 254: 117228, 2021 Feb 15.
Artículo en Inglés | MEDLINE | ID: mdl-33357842

RESUMEN

Bacterial cellulose (BC) is a natural polymer that has unique and interesting structural, physical and chemical properties. These characteristics make it very attractive as a starting point for several novel developments in innovative research. However, the pristine BC lacks certain properties, in particular, magnetic property, which can be imparted to BC by incorporation of several types of magnetic nanoparticles. Magnetic nanocomposites based on BC exhibit additional magnetic functionality on top of the excellent properties of pristine BC, which make them promising materials with potential uses in various medical and environmental applications, as well as in advanced electronic devices. This review has compiled information about all classes of BC magnetic nanocomposites fabricated by various synthesis approaches and an overview of applications as well as improved features of these materials. A summary of the key developments of BC magnetic nanocomposites and emphasis on novel advances in this field is presented.


Asunto(s)
Celulosa/química , Nanopartículas Magnéticas de Óxido de Hierro/química , Nanocompuestos/química , Polisacáridos Bacterianos/química , Adsorción , Animales , Bacterias/química , Materiales Biocompatibles/química , Celulosa/ultraestructura , Sistemas de Liberación de Medicamentos , Humanos , Hidrogeles/química , Nanopartículas Magnéticas de Óxido de Hierro/ultraestructura , Ciencia de los Materiales , Ensayo de Materiales , Microscopía Electrónica de Rastreo , Estructura Molecular , Nanocompuestos/ultraestructura , Nanofibras/química , Nanofibras/ultraestructura , Nanotecnología , Polisacáridos Bacterianos/ultraestructura , Ingeniería de Tejidos
17.
J Bacteriol ; 192(12): 3001-10, 2010 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-20348252

RESUMEN

The extracytoplasmic function sigma factor AlgU of Pseudomonas aeruginosa is responsible for alginate overproduction, leading to mucoidy and chronic infections of cystic fibrosis patients. We investigated here the role of AlgU in the formation of nonmucoid biofilms. The algU mutant of P. aeruginosa PAO1 (PAOU) showed a dramatic impairment in biofilm formation under dynamic conditions. PAOU was defective both in cell attachment to glass and in development of robust, shear-resistant biofilms. This was explained by an impaired production of extracellular matrix, specifically of the exopolysaccharide Psl, as revealed by microscopy and enzyme-linked immunosorbent assay. Complementing the algU mutation with a plasmid-borne algU gene restored wild-type phenotypes. Compared with that in PAO1, expression of the psl operon was reduced in the PAOU strain, and the biofilm formation ability of this strain was partially restored by inducing the transcription of the psl operon. Furthermore, expression of the lectin-encoding lecA and lecB genes was reduced in the PAOU strain. In agreement with the requirement of LecB for type IV pilus biogenesis, PAOU displayed impaired twitching motility. Collectively, these genetic downregulation events explain the biofilm formation defect of the PAOU mutant. Promoter mapping indicated that AlgU is probably not directly responsible for transcription of the psl operon and the lec genes, but AlgU is involved in the expression of the ppyR gene, whose product was reported to positively control psl expression. Expressing the ppyR gene in PAOU partially restored the formation of robust biofilms.


Asunto(s)
Proteínas Bacterianas/metabolismo , Biopelículas/crecimiento & desarrollo , Pseudomonas aeruginosa/clasificación , Pseudomonas aeruginosa/fisiología , Factor sigma/metabolismo , Proteínas Bacterianas/genética , Regulación Bacteriana de la Expresión Génica/fisiología , Lectinas , Mutación , Polisacáridos Bacterianos/biosíntesis , Polisacáridos Bacterianos/ultraestructura , Regiones Promotoras Genéticas , Pseudomonas aeruginosa/genética , Factor sigma/genética
18.
Int J Biol Macromol ; 161: 1516-1525, 2020 Oct 15.
Artículo en Inglés | MEDLINE | ID: mdl-32755710

RESUMEN

Broadband dielectric spectroscopy was used to investigate the molecular α-relaxation of the exopolysaccharides (EPS) extracted from Nostoc commune cyanobacteria. The EPS were modified in different ways. EPS were carboxymethylated to obtain carboxymethyl-exopolysaccharides (CEPS). EPS and CEPS were doped with ammonium iodide and 1-butyl-3-methylimidazolium chloride. An α relaxation process was observed for all specimens. The temperature dependence of the relaxation times for pure and doped, EPS and CEPS polymers exhibited non-Arrhenius behavior. This relaxation process was associated with the glass transition of the complex heteropolysaccharides produced by the cyanobacteria. The molecular mobility at the glass transition, Tg, was affected by both the carboxymethylation treatment and the doping. The fragility index also decreased for the doped specimens, which may be attributed to an increase in the mobility of the polymer chains due to the plasticizing effect of the doping agents.


Asunto(s)
Nostoc commune/química , Polisacáridos Bacterianos/química , Polisacáridos Bacterianos/aislamiento & purificación , Fraccionamiento Químico , Monosacáridos/química , Polisacáridos Bacterianos/ultraestructura , Análisis Espectral , Temperatura
19.
Int J Biol Macromol ; 156: 565-575, 2020 Aug 01.
Artículo en Inglés | MEDLINE | ID: mdl-32311401

RESUMEN

In this study, we investigated the gellan gelation mechanism induced by Glucono-δ-lactone (GDL) addition, and subsequently we further fabricated a series of thermally irreversible emulsion gels with the GDL-induced gel matrix as the continuous phase and the methyl cellulose (MC) stabilized emulsion as the dispersed phase. The results showed that GDL- induced gellan gelation was both a time- and temperature-dependent process, which was similar to the gelation process of NaCl-induced gellan gels, but with a higher temperature-dependence. Moreover, GDL-induced gel had a significantly higher rupture strength and the resulting gel did not melt on heating, meaning that the GDL-induced gellan gel can be deemed thermally irreversible. This is because decreasing pH is commonly more effective in promoting gellan gelation. Besides, by mixing the MC-stabilized emulsion with a hot gellan sol, followed by adding GDL, we fabricated the emulsion gels with a wide range of oil phase fraction (0-30%). The emulsion gels exhibited good thermal stability, without melting and oil droplet coalescence observed when heating the gels in a boiling water bath for 30 min. Conclusively, our results may deepen the understanding on gellan gelation induced by GDL and also broaden the utilization of gellan in building gel-related food structures.


Asunto(s)
Emulsiones , Geles/química , Gluconatos/química , Lactonas/química , Polisacáridos Bacterianos/química , Temperatura , Fenómenos Mecánicos , Polisacáridos Bacterianos/ultraestructura , Reología
20.
Int J Biol Macromol ; 151: 984-992, 2020 May 15.
Artículo en Inglés | MEDLINE | ID: mdl-31733253

RESUMEN

Exopolysaccharides (EPS) are microbially-originated, complex biosynthetic polymers, mainly carbohydrates in nature. They have gained attention of modern researches due to their novel physicochemical characteristics. However, the development of cost-effective strategies to improve the EPS yield, remains a challenge. In this study, cost-effective EPS production was carried out from B. licheniformis in solid state fermentation of mango peels substrate with waste-to-value theme. Initially, B. licheniformis was exposed to ultraviolet (UV) radiations of short wavelength which significantly improved the EPS yield (from 3.4 to 4.6 g/L). The highest EPS producing mutant strain (B. licheniformis MS3) was further proceeded for yield optimization using RSM-CCD approach. Optimization improved the yield >3.2-folds (from 4.6 to 15.6 g/L). The optimally yielded fraction was characterized using HPLC, FT-IR and SEM analyses. HPLC revealed the hetero-polymeric nature of EPS containing mannose (20.60%), glucose (46.80%), and fructose (32.58%) subunits. FT-IR spectroscopy revealed the presence of hydroxyl and carboxyl functional groups, and glycosidic linkages among monosaccharides. SEM microstructure showed that EPS comprise smoother surface with less porosity. Studies on functional characteristics revealed the presence of hydrophilic moieties among EPS with moderate water (105.3%) and oil (86.3%) uptake capacity. The EPS exhibited excellent emulsifying properties showed good stability against all hydrocarbons/oils tested. In conclusion, the cost-effective EPS production with multifunctional properties, this study may be valuable for various biochemical and biotechnological sectors.


Asunto(s)
Bacillus licheniformis/química , Polisacáridos Bacterianos/química , Bacillus licheniformis/metabolismo , Emulsiones , Fermentación , Ingeniería Metabólica , Estructura Molecular , Monosacáridos/análisis , Mutagénesis , Polisacáridos Bacterianos/biosíntesis , Polisacáridos Bacterianos/ultraestructura , Solubilidad , Análisis Espectral , Relación Estructura-Actividad
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