Polar Polysaccharide Research Articles

The Effectiveness Antimicrobial of Polysaccharide Gel from Durian Peel Ethanol Extract and Chitosan Gel

BACKGROUND: Research on galenic bioactive compounds as antimicrobial agents needs to be developed. Durian peel ethanol extract is a polar polysaccharide consisting of D-galacturonic acid with -1,4 glycosidic bonds and can form a polysaccharide gel. Chitosan can be synthesized through the deacetylation of chitin as a compound (1.4)-2 amino-2deoxy D-glucopyranose and can form a gel in 1.5–2% acetic acid. The properties of chitosan are biodegradable, non-toxic, polycationic antimicrobial, and biocompatible. AIM: The study aimed to determine the effectiveness of the ethanolic extract of PG durian peel and CG as antimicrobial agents. METHODS: The research design was an experimental study and conducted at the Microbiology Laboratory, Faculty of Health, Setia Budi University, Surakarta, in August–December 2020. The research stages were the extraction of durian skin polysaccharides, bioformulation of PG durian peel extract and CG, and antimicrobial activity testing using the diffusion method. RESULTS: The results showed PG durian peel ethanolic extract concentration (100%, 50%, 25%, 12.5%, 1.5%, and CG 1.5% %) or a combination of durian peel extract PG (1.5%) and CG (1.5%) 1:1 ratio; 1:2; 2:1 was antimicrobial against Staphylococcus aureus ATCC 25923, Bacillus subtilis ATCC 6633, Escherichia coli ATCC 25922, Salmonella typhi ATCC 13311, Pseudomonas aeruginosa ATCC 27853, and Candida albicans ATCC 10231. PG durian peel ethanolic extract concentration of 100%, 50%, 25%, 12.5%, 1.5%, and CG 1.5% or a combination of durian peels ethanolic extract PG (1.5%) and CG (1.5%) ratio 1:1; 1:2; and 2:1 as an antimicrobial in vitro. CONCLUSION: PG durian peels ethanolic extract concentration 100% showed optimum effectiveness as an antimicrobial against B. subtilis ATCC 6633. Chitosan 1.5% showed optimal effectiveness as an antimicrobial against P. aeruginosa ATCC 27853. The effectiveness of the mixture of PG 1.5% and CG 1.5% ratio 1:2 showed optimum effectiveness against all test cultures.

A Multiprotein Complex Anchors Adhesive Holdfast at the Outer Membrane of Caulobacter crescentus.

Adhesion allows microbes to colonize surfaces and is the first stage in biofilm formation. Stable attachment of the freshwater alphaproteobacterium Caulobacter crescentus to surfaces requires an adhesive polysaccharide called holdfast, which is synthesized at a specific cell pole and ultimately found at the tip of cylindrical extensions of the cell envelope called stalks. Secretion and anchoring of holdfast to the cell surface are governed by proteins HfsDAB and HfaABD, respectively. The arrangement and organization of these proteins with respect to each other and the cell envelope, and the mechanism by which the holdfast is anchored on cells, are unknown. In this study, we have imaged a series of C. crescentus mutants using electron cryotomography, revealing the architecture and arrangement of the molecular machinery involved in holdfast anchoring in cells. We found that the holdfast is anchored to cells by a defined complex made up of the HfaABD proteins and that the HfsDAB secretion proteins are essential for proper assembly and localization of the HfaABD anchor. Subtomogram averaging of cell stalk tips showed that the HfaABD complex spans the outer membrane. The anchor protein HfaB is the major component of the anchor complex located on the periplasmic side of the outer membrane, while HfaA and HfaD are located on the cell surface. HfaB is the critical component of the complex, without which no HfaABD complex was observed in cells. These results allow us to propose a working model of holdfast anchoring, laying the groundwork for further structural and cell biological investigations.IMPORTANCE Adhesion and biofilm formation are fundamental processes that accompany bacterial colonization of surfaces, which are of critical importance in many infections. Caulobacter crescentus biofilm formation proceeds via irreversible adhesion mediated by a polar polysaccharide called holdfast. Mechanistic and structural details of how the holdfast is secreted and anchored on cells are still lacking. Here, we have assigned the location and described the arrangement of the holdfast anchor complex. This work increases our knowledge of the relatively underexplored field of polysaccharide-mediated adhesion by identifying structural elements that anchor polysaccharides to the cell envelope, which is important in a variety of bacterial species.

Aqueous extract of Costus arabicus inhibits calcium oxalate crystal growth and adhesion to renal epithelial cells.

Costus arabicus L. (C. arabicus) is a plant used in Brazilian folk medicine to treat urolithiasis; however, its mechanism of action is unclear. The interaction between calcium oxalate (CaOx) crystals and the renal epithelium is important in calculogenesis, and compounds that modulate this process represent candidate therapeutic agents for stone prevention. Therefore, we assessed the inhibitory activity of C. arabicus on CaOx crystallization and the interaction of CaOx crystals with the renal epithelium. A seeded CaOx monohydrate (COM) crystallization system was used to study the effect of C. arabicus on crystal growth. Madin Darby canine kidney (MDCK) cells were used to study [(14)C] COM crystal adhesion in the presence and absence of an aqueous extract of C. arabicus. Cytotoxicity was assessed using a tetrazolium (MTS) cell proliferation assay. Aqueous extracts of C. arabicus decreased crystal growth in a concentration-dependent fashion. Precoating crystals with C. arabicus extract prevented their adhesion to MDCK cells, while pretreating cells did not show any effect. The extract was non-cytotoxic in concentrations of at least 1 mg/ml, which is likely above concentrations achievable in the urine following oral ingestion and excretion. No inhibitory activity was found in hexane, methyl chloride, n-butanol and ethyl acetate fractions of an ethanol extract of the herb. An aqueous extract of C. arabicus may disrupt calculogenesis by interacting with CaOx crystal surfaces. Activity was present in the aqueous extract; therefore, this agent may be bioavailable when administered orally. Fractionation results suggest that the active agent might be a polar polysaccharide. Further identification and characterization along these lines may be warranted.

The effect of structural compositions on the biosorption of phenanthrene and pyrene by tea leaf residue fractions as model biosorbents

To enhance the removal efficiency of polycyclic aromatic hydrocarbons (PAHs) by natural biosorbent, sorption of phenanthrene and pyrene onto raw and modified tea leaves as a model biomass were investigated. Tea leaves were treated using Soxhlet extraction, saponification, and acid hydrolysis to yield six fractions. The structures of tea leaf fractions were characterized by elemental analysis, Fourier transform infrared (FTIR) spectroscopy, and scanning electron microscopy (SEM). The amorphous cellulose components regulated the sorption kinetics, capacity, and mechanism of biomass fractions. The adsorption kinetics fit well to pseudo-second-order model and isotherms followed the Freundlich equation. By the consumption of the amorphous cellulose under acid hydrolysis, both the aliphatic moieties and aromatic domains contributed to total sorption, thus sorption capacities of the de-sugared fractions were dramatically increased (5–20-fold for phenanthrene and 8–36-fold for pyrene). All de-sugared fractions exhibited non-linear sorption due to strong specific interaction between PAHs and exposed aromatic domains of biosorbent, while presenting a relative slow rate because of the condensed domain in de-sugared samples. The availability of strong sorption phases (aromatic domains) in the biomass fractions were controlled by polar polysaccharide components, which were supported by the FTIR, CHN, and SEM data.

Physiochemical Properties of Caulobacter crescentus Holdfast: A Localized Bacterial Adhesive

To colonize surfaces, the bacterium Caulobacter crescentus employs a polar polysaccharide, the holdfast, located at the end of a thin, long stalk protruding from the cell body. Unlike many other bacteria which adhere through an extended extracellular polymeric network, the holdfast footprint area is tens of thousands times smaller than that of the total bacterium cross-sectional surface, making for some very demanding adhesion requirements. At present, the mechanism of holdfast adhesion remains poorly understood. We explore it here along three lines of investigation: (a) the impact of environmental conditions on holdfast binding affinity, (b) adhesion kinetics by dynamic force spectroscopy, and (c) kinetic modeling of the attachment process to interpret the observed time-dependence of the adhesion force at short and long time scales. A picture emerged in which discrete molecular units called adhesins are responsible for initial holdfast adhesion, by acting in a cooperative manner.

The adhesive and cohesive properties of a bacterial polysaccharide adhesin are modulated by a deacetylase

Bacterial exopolysaccharide synthesis is a prevalent and indispensible activity in many biological processes, including surface adhesion and biofilm formation. In Caulobacter crescentus, surface attachment and subsequent biofilm growth depend on the ability to synthesize an adhesive polar polysaccharide known as the holdfast. In this work, we show that polar polysaccharide synthesis is a conserved phenomenon among Alphaproteobacterial species closely related to C. crescentus. Among them, mutagenesis of Asticcacaulis biprosthecum showed that disruption of the hfsH gene, which encodes a putative polysaccharide deacetylase, leads to accumulation of holdfast in the culture supernatant. Examination of the hfsH deletion mutant in C. crescentus revealed that this strain synthesizes holdfast; however, like the A. biprosthecum hfsH mutant, the holdfasts are shed into the medium and have decreased adhesiveness and cohesiveness. Site-directed mutagenesis at the predicted catalytic site of C. crescentus HfsH phenocopied the ΔhfsH mutant and abolished the esterase activity of HfsH. In contrast, overexpression of HfsH increased cell adherence without increasing holdfast synthesis. We conclude that the polysaccharide deacetylase activity of HfsH is required for the adhesive and cohesive properties of the holdfast, as well as for the anchoring of the holdfast to the cell envelope.

The polar polysaccharide capsule of Hyphomonas adhaerens MHS-3 has a strong affinity for gold.

Select groups of bacteria, including prothescate species, have an unusual capacity to sequester gold and bioconcentrate it to very high levels. Hyphomonas adhaerens MHS-3 (MHS-3) is one such species, as demonstrated by Energy Dispersive Spectroscopy. Transmission electron microscopy revealed that the binding site was specific on the polar polysaccharide capsule. A capsuleless mutant and periodate-treated wild type did not sequester gold. The gold may interact with the same sites in the capsule that naturally adhere MHS-3 to surfaces in the marine environment.

Re-evaluation of osmotic effects as a general adaptative strategy for bacteria in sub-freezing conditions

We studied the molecular mechanisms of adaptation of a Siberian psychrophilic bacterial strain. Upon adaptation to 4°C from 24°C, the major changes observed were in the membrane and cell surface chemistry. There was no evidence for the formation of so-called ‘compatible metabolites’ that are thought to be responsible for the survival at very low to sub-freezing temperatures. The membrane fatty acids were shorter with an increased amount of unsaturation in the 4°C cells compared to the 24°C cells. The absence of a significant amount of phosphorylation in the membrane lipids at 4°C compared to the levels at 24°C was another significant difference. At 4°C, the cell size was reduced in volume by a factor of ∼14 compared to its size at 24°C. The polar polysaccharide capsular layer was also significantly reduced. There were no significant changes in the protein profiles indicating that antifreeze proteins were not being produced. The results obtained here are consistent with observations and established theories and principles on and about the behavior of water in confined spaces. These indicate that ordering effects, surface charge and polarity are the key determinants of the freezing point and the type of ice structure that will be formed when water is confined to an area of the size of a bacterial cell.