Glucose Polymer Research Articles

Oral mitis group streptococci: A silent majority in our oral cavity.

Members of the oral mitis group streptococci including Streptococcus oralis, Streptococcus sanguinis, and Streptococcus gordonii are the most abundant inhabitants of human oral cavity and dental plaque, and have been implicated in infectious complications such as bacteremia and infective endocarditis. Oral mitis group streptococci are genetically close to Streptococcus pneumoniae; however, they do not produce cytolysin (pneumolysin), which is a key virulence factor of S. pneumoniae. Similar to S. pneumoniae, oral mitis group streptococci possess several cell surface proteins that bind to the cell surface components of host mammalian cells. S. sanguinis expresses long filamentous pili that bind to the matrix proteins of host cells. The cell wall-anchored nuclease of S. sanguinis contributes to the evasion of the neutrophil extracellular trap by digesting its web-like extracellular DNA. Oral mitis group streptococci produce glucosyltransferases, which synthesize glucan (glucose polymer) from sucrose of dietary origin. Neuraminidase (NA) is a virulent factor in oral mitis group streptococci. Influenza type A virus (IAV) relies on viral NA activity to release progeny viruses from infected cells and spread the infection, and NA-producing oral streptococci elevate the risk of IAV infection. Moreover, oral mitis group streptococci produce hydrogen peroxide (H2 O2 ) as a by-product of sugar metabolism. Although the concentrations of streptococcal H2 O2 are low (1-2 mM), they play important roles in bacterial competition in the oral cavity and evasion of phagocytosis by host macrophages and neutrophils. In this review, we intended to describe the diverse pathogenicity of oral mitis group streptococci.

The fragility of liver glycogen from humans with type 2 diabetes: A pilot study

Liver glycogen is a highly branched glucose polymer found as β particles (~20 nm in diameter), which can bind together into larger composite α particles. Hepatic α particles have been shown to be structurally fragile (breaking up into smaller particles in certain solvents) in mouse models of diabetes; if occurring in vivo, the resulting small glycogen particles could exacerbate the poor blood-sugar homeostasis characteristic of the disease. Here we tested if this α-particle fragility also occurred in liver glycogen obtained from humans with diabetes. It was found that liver glycogen from diabetic humans was indeed more fragile than from non-diabetic humans, which was also seen in the mouse experiments we ran in parallel. Proteomic analysis revealed three candidate proteins from differentially expressed glycogen proteins (Diabetes/ Non-diabetes) in both human and mouse groups. Identifying these proteins may give clues to the binding mechanism that holds together α particles together, which, being different in diabetic glycogen, is relevant to diabetes prevention and management.

Bacteria loaded with glucose polymer and photosensitive ICG silicon-nanoparticles for glioblastoma photothermal immunotherapy

Bacteria can bypass the blood-brain barrier (BBB), suggesting the possibility of employment of bacteria for combating central nervous system diseases. Herein, we develop a bacteria-based drug delivery system for glioblastoma (GBM) photothermal immunotherapy. The system, which we name as ‘Trojan bacteria’, consists of bacteria loaded with glucose polymer and photosensitive ICG silicon-nanoparticles. In an orthotopic GBM mouse model, we demonstrate that the intravenously injected bacteria bypass the BBB, targeting and penetrating GBM tissues. Upon 808 nm-laser irradiation, the photothermal effects produced by ICG allow the destruction of bacterial cells and the adjacent tumour cells. Furthermore, the bacterial debris as well as the tumour-associated antigens promote antitumor immune responses that prolong the survival of GBM-bearing mice. Moreover, we demonstrate the residual bacteria are effectively eliminated from the body, supporting the potential therapeutic use of this system.

In Vivo Digestibility of Carbohydrate Rich in Isomaltomegalosaccharide Produced from Starch by Dextrin Dextranase.

Slowly digestible carbohydrates are needed for nutritional support in diabetic patients with malnutrition. They are a good source of energy and have the advantage that their consumption produces a low postprandial peak in blood glucose levels because they are slowly and completely digested in the small intestine. A high-amount isomaltomegalosaccharide containing carbohydrate (H-IMS), made from starch by dextrin dextranase, is a mixture of glucose polymers which has a continuous linear structure of α-1,6-glucosidic bonds and a small number of α-1,4-glucosidic bonds at the reducing ends. It has a broad degree of polymerization (DP) distribution with glucans of DP 10－30 as the major component. In our previous study, H-IMS has been shown to exhibit slow digestibility in vitro and not to raise postprandial blood glucose to such levels as that raised by dextrin in vivo. This marks it out as a potentially useful slowly digestible carbohydrate, and this study aimed to evaluate its in vivo digestibility. The amount of breath hydrogen emitted following oral administration of H-IMS was measured to determine whether any indigestible fraction passed through to and was fermented in the large intestine. Total carbohydrate in the feces was also measured. H-IMS, like glucose and dextrin, did not result in breath hydrogen excretion. Carbohydrate excretion with dietary H-IMS was no different from that of glucose or water. These results show that the H-IMS is completely digested and absorbed in the small intestine, indicating its potential as a slowly digestible carbohydrate in the diet of diabetic patients.

PLG-007 and Its Active Component Galactomannan-α Competitively Inhibit Enzymes That Hydrolyze Glucose Polymers.

PLG-007 is a developmental therapeutic compound that has been clinically shown to reduce the magnitude of postprandial glucose excursions and has the potential to be an adjunct treatment for diabetes and inflammatory-related diseases. The present investigation is aimed at understanding the molecular mechanism of action of PLG-007 and its galactomannan (GM) components GMα and GMβ (in a 1:4 mass ratio, respectively) on enzyme (i.e., α-amylase, maltase, and lactase) hydrolysis of glucose polymers using colorimetric assays and 13C HSQC NMR spectroscopy. The starch–iodine colorimetric assay indicated that GMα strongly inhibits α-amylase activity (~16-fold more potent than GMβ) and thus is the primary active component in PLG-007. 13C HSQC experiments, used to follow the α-amylase-mediated hydrolysis of starch and amylopectin, further demonstrate the α-amylase inhibitory effect of GMα via α-amylase-mediated hydrolysis of starch and amylopectin. Maltohexaose (MT6) was used to circumvent the relative kinetic complexity of starch/amylopectin degradation in Michaelis–Menten analyses. The Vmax, KM, and Ki parameters were determined using peak volume integrals from 13C HSQC NMR spectra. In the presence of PLG-007 with α-amylase and MT6, the increase in KM from 7.5 ± 0.6 × 10−3 M (control) to 21 ± 1.4 × 10−3 M, with no significant change in Vmax, indicates that PLG-007 is a competitive inhibitor of α-amylase. Using KM values, Ki was estimated to be 2.1 ± 0.9 × 10−6 M; however, the microscopic Ki value of GMα is expected to be larger as the binding stoichiometry is likely to be greater than 1:1. Colorimetric assays also demonstrated that GMα is a competitive inhibitor of the enzymes maltase and lactase. Overall, this study provides insight as to how PLG-007 (GMα) is likely to function in vivo.

Mixotrophic Denitrification of Glucose Polymer-Based Pyrite Tailings for Enhanced Nitrogen and Phosphorus Removal of Municipal Tailwater

In order to improve the removal ability of nitrogen and phosphorus pollutants from sewage with low C/N ratio, this study prepared the glucose polymer-based pyrite tailings with core-shell structure through glucose polymerizing on the surface of pyrite tailings particles and constructed a heterotrophic-sulfur autotrophic mixed-denitrification system. The experimental results show that compared with ordinary pyrite tailings, pyrite tailings modified by glucose polymer can improve the water quality of pH, enhance the ability to remove NO3− in water, and prolong the ability of mineral to continuously treat sewage, which also has a good removal effect on PO43− in water. The results of this study are of great significance to solve the excessive nitrogen and phosphorus in the secondary effluent and alleviate the eutrophication of the natural water.

Starch Biosynthetic Protein Complex Formation in Rice ss2a be2b (+) Double Mutant Differs from Their Parental Single Mutants.

Amylopectin, which consists of highly branched glucose polymers, is a major component of starch. Biochemical processes that regulate the elongation of glucose polymers and the generation and removal of glucose branches are essential for determining the properties of starch. Starch synthases (SSs) and branching enzyme (BE) mainly form complexes consisting of SSI, SSIIa, and BEIIb during endosperm development. Loss of BEIIb in rice is complemented by BEIIa, but the compensatory effects differ depending on the presence or absence of inactive BEIIb. To better understand these compensatory mechanisms, ss2a be2b (+) double mutant, which possessed truncated inactive SSIIa and inactive BEIIb, were analyzed. Soluble proteins separated by gel filtration chromatography showed that SSIIa and BEIIb proteins in the wild-type exhibited a broad range of elution patterns and only small amounts were detected in high molecular mass fractions. In contrast, most of truncated inactive SSIIa and inactive BEIIb from ss2a be2b (+) were found in high molecular mass fractions, and the SSI-SSIIa-BEIIb trimeric protein complex found in the wild-type was likely absent in ss2a be2b (+). Those SSIIa and BEIIb proteins in high molecular mass fractions in ss2a be2b (+) were also identified by mass spectrometry. Parental ss2a single mutant had negligible amounts of SSIIa suggesting that the truncated inactive SSIIa was recruited to high-molecular mass complexes in the presence of inactive BEIIb in ss2a be2b (+) double mutant. In addition, SSIVb might be involved in the formation of alternative protein complexes with < 300 kDa in ss2a be2b (+).

MO665: 2 Icodextrin (2-ICO) Dwells in Peritoneal Dialysis (PD) Patients: One Center Experience

Abstract BACKGROUND AND AIMS Icodextrin is a soluble glucose polymer used widely as an alternative osmotic agent to glucose-only solutions in PD patients. It provides effective net peritoneal ultrafiltration (UF) and nowadays it is only licensed for once-daily dwells. However, in selected patients it has been described its use in two daily dwells (2-ICO). Our aim was to revise our center experience with icodextrin when prescribed as 2-ICO. METHOD We retrospectively analysed all patients with a 2-ICO dwell prescription in our PD unit from January 2018 until June 2021. Clinical data, indication for prescription and outcomes were collected. RESULTS CONCLUSION In selected patients, 2-ICO dwells daily may have a clinical benefit, improving UF significantly and allowing better management of fluid overload and UF failure without relevant adverse events.

Biophysical and Structural Characterization of Glucan Phosphatase SEX4 from Zea mays

Plants store energy in starch, a glucan made of two polymers of glucose‐ amylose and amylopectin. Phosphorylation, the only known in vivo modification of starch, controls the structure, function, and physicochemical properties of the starch granule and thereby modulates the starch degradation at night. Reversible starch phosphorylation has been increasingly appreciated as a key regulatory step controlling diurnal starch metabolism. Glucan phosphatase Starch Excess4 (SEX4) is an allosteric enzyme that binds to and dephosphorylates starch at the C6 and C3 positions of glucose residues. Plants lacking glucan phosphatases exhibit excess starch and starch with increased phosphorylation. However, our understanding of how SEX4 binds to the semicrystalline starch stricture and regulates the dephosphorylation mechanism is incomplete. Previously, the x‐ray crystal structure of catalytically inactive Arabidopsis thaliana SEX4 bound to maltohexaose has been described. Here we present the x‐ray crystal structure of wild‐type SEX4 from Zea mays to a resolution of 2.9 A. Utilizing hydrogen‐deuterium exchange spectroscopy and differential scanning fluorometry, we intend to understand how SEX4 interacts with its glucan substrate for an efficient starch dephosphorylation mechanism. We also investigated the ability of SEX4 to enhance in‐vitro starch degradation. Our findings reveal that SEX4 from cereal crops such as Zea mays has the increased ability to enhance starch degradation than the SEX4 orthologs from storage crops.

Macromolecular Crowding Slows Glutamate Dehydrogenase Kinetics

Most of our understanding of enzyme kinetics is based on experiments conducted in dilute solution, which does not accurately represent crowded cellular environments. Cells contain high concentrations (300‐400g/L) of various macromolecules such as proteins, carbohydrates and ribosomes. This crowding reduces the volume of solvent available for other molecules in the solution and has previously been shown to impact the behavior of enzymes. To study these potential consequences, the Michaelis‐Menten kinetics of glutamate dehydrogenase (GDH) was monitored in the presence of high concentrations of “crowding agents” such as dextran, a glucose polymer. Given this enzyme’s central role at interface of nitrogen and carbohydrate metabolism, GDH is highly regulated. Our results suggest that crowding may influence this regulation. For example, leucine is a less effective activator of GDH in the presence of dextran. Furthermore, crowding enhances substrate inhibition of GDH in a pH‐dependent manner. The resulting effects from crowding were substrate dependent such that the presence of dextran decreased the Vmax more with the NADP+ cofactor than with NAD+. Both dextran and BSA decreased the Km of NADP+ but did not affect NAD+. The effects of crowding on the enthalpy (ΔH҂) and entropy (ΔS҂) of activations determined from Eyring plots also were also substrate and pH‐dependent. Overall, these results highlight the importance of studying enzymes especially heavily regulated ones like GDH under crowded conditions that more realistically mimic the crowded cellular environment.

Effect of pH Dependent Substrate Inhibition on Glutamate Dehydrogenase Kinetics

Glutamate dehydrogenase (GDH) serves as the main regulated enzyme linking protein and carbohydrate metabolism. This enzyme converts the amino acid glutamate to the TCA intermediate, α‐ketoglutarate. While dysregulation of GDH is linked to hyperinsulinism and other diseases, the kinetics this enzyme of have only been analyzed under dilution conditions. However, cells are more crowded than these buffer solutions frequently used to collect enzyme kinetics data because their cytoplasm contains high concentrations of proteins, carbohydrates, and other macromolecules. Evidence has shown that this macromolecular crowding slow diffusion rates and changes protein conformations, which alters the kinetics of enzymes. Scientists often mimic the crowded environment of a cell using large, synthetic polymers, such as dextran, a glucose polymer, which excludes volume to other biological molecules in the same solution. While several studies have characterized these excluded volume effects on enzyme kinetics, this is the first study to analyze the effects of crowding on enzyme inhibition. Investigating how inhibitors like GTP and activators like leucine effect the kinetics of GDH will provide a deeper understanding of the regulation of this enzyme inside out bodies. Furthermore, saturating amounts of glutamate results in substrate inhibition of GDH by forming a “dead end complex” comprised of glutamate, NADH, and GDH at low pH values. To understand the effects of crowding on substrate inhibition, GDH Michaelis Menten kinetics were analyzed in the presence and absence of dextran at four pH values. These assays were repeated with glucose, the monomer of dextran as a control to separate chemical effects from excluded volume effects caused by the large size of dextran. The presence of dextran resulted in more substrate inhibition than in the presence of glucose and this inhibition that was observed at higher pH values than in buffer alone. Leucine, a known activator of GDH, operates by destabilizing the dead‐end complex. While the presence of leucine decreases substrate inhibition in dilute conditions, this compound was unable to active GDH in the presence of dextran. Overall, these results suggest that crowding promotes substrate inhibition by stabilizing the dead‐end complex of GDH which is a stronger interaction than leucine dissociation of the dead‐end complex. Therefore, macromolecular crowding in a cell could provide an additional level of regulation on GDH inside cells.

Biochemical Characterization of Starch Excess4 from Storage Crops

Starch is a water‐insoluble branched polymer of glucose. Its degradation requires the concerted action of glucan phosphatases and glucan dikinases. Reversible starch phosphorylation allows for the solubilization of the starch surface, allowing for amylase to degrade starch into maltose units. However, our understanding is limited on how these enzymes contribute to starch degradation in storage crops such as potato and cassava. In this study, we biochemically characterized cassava and potato SEX4 enzymes using enzymatic assays and differential scanning fluorometry. We determined the kinetics of SEX4 using both generic and physiologically relevant substrates. We also explored the utilization of these glucan phosphatase orthologs to enhance starch degradation in‐vitro. Our findings reveal that cassava and potato SEX4 show similar allosteric activation mechanisms but varying abilities to degrade starch under in‐vitro conditions.

Investigation into the Structure and Activity of the Arabidopsis β‐amylase BAM1

Starch in plants is a large polymer of glucose that stores excess glucose for times of limited photosynthesis. Starch is used in many industrial processes such as laundry and papermaking. In plants, regulation of starch storage and degradation is a multifaceted system that allows the plant to adjust carbohydrate storage in response to a variety of environmental and developmental conditions. However, we are unsure how this process is regulated. β‐amylases (BAMs) hydrolyze starch to produce maltose. Plants contain many BAM proteins and possibly each has a unique function and regulatory mechanism, although this is an area of active research. The degradation of starch by BAM1 is activated when the plant undergoes osmotic stress. BAM1 is suggested to be regulated by a redox reaction, however, the precise regulatory mechanism is unclear although it is thought to involve disulfide formation between an N‐terminal cysteine and another within the amylase domain. A better understanding of the structure and the activity of BAM1 will allow us to improve many crucial industries. To address the structure of BAM1, we purified the protein from E. coli cells and ensured that the protein was folded using circular dichroism. We then collected small‐angle X‐ray scattering (SAXS) data on BAM1 and analyzed the data to determine solution dimensions of BAM1. Those data were then compared against SAXS data of other BAM proteins collected in our lab. The preliminary SAXS data and comparison support BAM1 being a monomeric protein with an extended N‐terminus. Another part of this project was to determine the activity of BAM1 and whether the activity is affected by oxidation. We are optimizing the Bicinchoninic acid (BCA) assay, as well as a maltose‐binding protein green fluorescent protein (MBP‐GFP) assay to investigate the activity of BAM1 and the effects of oxidizing conditions. Further investigation into the disulfide bond will be done using DSF, and CD.

32Starch metabolism in potato Solanum tuberosum L.

Starch is a major storage carbohydrate in plants. It is an important source of calories in the human and animal diet. Also, it is widely used in various industries. Native starch consists of water-insoluble semicrystalline granules formed by natural glucose polymers amylose and amylopectin. The physicochemical properties of starch are determined by the amylose:amylopectin ratio in the granule and degrees of their polymerization and phosphorylation. Potato Solanum tuberosum L. is one of the main starch-producing crops. Growing industrial needs necessitate the breeding of plant varieties with increased starch content and specified starch properties. This task demands detailed information on starch metabolism in the producing plant. It is a complex process, requiring the orchestrated work of many enzymes, transporter and targeting proteins, transcription factors, and other regulators. Two types of starch are recognized with regard to their biological functions. Transitory starch is synthesized in chloroplasts of photosynthetic organs and degraded in the absence of light, providing carbohydrates for cell needs. Storage starch is synthesized and stored in amyloplasts of storage organs: grains and tubers. The main enzymatic reactions of starch biosynthesis and degradation, as well as carbohydrate transport and metabolism, are well known in the case of transitory starch of the model plant Arabidopsis thaliana. Less is known about features of starch metabolism in storage organs, in particular, potato tubers. Several issues remain obscure: the roles of enzyme isoforms and different regulatory factors in tissues at various plant developmental stages and under different environmental conditions; alternative enzymatic processes; targeting and transport proteins. In this review, the key enzymatic reactions of plant carbohydrate metabolism, transitory and storage starch biosynthesis, and starch degradation are discussed, and features specific for potato are outlined. Attention is also paid to the known regulatory factors affecting starch metabolism

From Brown Seaweed to a Sustainable Microbial Feedstock for the Production of Riboflavin.

The increasing global demand for food and energy production encourages the development of new production strategies focused on sustainability. Often, microbial bioprocesses rely on food or feed competitive feedstocks; hence, there is a trending need for green substrates. Here, we have proven the potential of brown seaweed biomass as microbial feedstock on account of its content of mannitol and the glucose polymer laminarin. Our host, Corynebacterium glutamicum, was engineered to enable access to mannitol as a carbon source through the heterologous expression of the mannitol-specific phosphotransferase system and the mannitol-1-phosphate-5-dehydrogenase from Bacillus subtilis. Overproduction of riboflavin was coupled with mannitol and glucose consumption via constitutive overexpression of the biosynthetic riboflavin operon ribGCAH from C. glutamicum. Brown seaweed extract and brown seaweed hydrolysate from Laminaria hyperborea, containing mannitol and glucose, were used as a carbon source for flask and bioreactor fermentations. In a seaweed-based fed-batch fermentation, the riboflavin final titer, yield, and volumetric productivity values of 1,291.2 mg L−1, 66.1 mg g−1, and 17.2 mg L−1 h−1, respectively, were achieved.

More Prominent Inflammatory Response to Pachyman than to Whole-Glucan Particle and Oat-β-Glucans in Dextran Sulfate-Induced Mucositis Mice and Mouse Injection through Proinflammatory Macrophages.

(1→3)-β-D-glucans (BG) (the glucose polymers) are recognized as pathogen motifs, and different forms of BGs are reported to have various effects. Here, different BGs, including Pachyman (BG with very few (1→6)-linkages), whole-glucan particles (BG with many (1→6)-glycosidic bonds), and Oat-BG (BG with (1→4)-linkages), were tested. In comparison with dextran sulfate solution (DSS) alone in mice, DSS with each of these BGs did not alter the weight loss, stool consistency, colon injury (histology and cytokines), endotoxemia, serum BG, and fecal microbiome but Pachyman–DSS-treated mice demonstrated the highest serum cytokine elicitation (TNF-α and IL-6). Likewise, a tail vein injection of Pachyman together with intraperitoneal lipopolysaccharide (LPS) induced the highest levels of these cytokines at 3 h post-injection than LPS alone or LPS with other BGs. With bone marrow-derived macrophages, BG induced only TNF-α (most prominent with Pachyman), while LPS with BG additively increased several cytokines (TNF-α, IL-6, and IL-10); inflammatory genes (iNOS, IL-1β, Syk, and NF-κB); and cell energy alterations (extracellular flux analysis). In conclusion, Pachyman induced the highest LPS proinflammatory synergistic effect on macrophages, followed by WGP, possibly through Syk-associated interactions between the Dectin-1 and TLR-4 signal transduction pathways. Selection of the proper form of BGs for specific clinical conditions might be beneficial.

Engineering microparticles based on solidified stem cell secretome with an augmented pro-angiogenic factor portfolio for therapeutic angiogenesis.

Tissue (re)vascularization strategies face various challenges, as therapeutic cells do not survive long enough in situ, while the administration of pro-angiogenic factors is hampered by fast clearance and insufficient ability to emulate complex spatiotemporal signaling. Here, we propose to address these limitations by engineering a functional biomaterial capable of capturing and concentrating the pro-angiogenic activities of mesenchymal stem cells (MSCs).In particular, dextran sulfate, a high molecular weight sulfated glucose polymer, supplemented to MSC cultures, interacts with MSC-derived extracellular matrix (ECM) components and facilitates their co-assembly and accumulation in the pericellular space. Upon decellularization, the resulting dextran sulfate-ECM hybrid material can be processed into MIcroparticles of SOlidified Secretome (MIPSOS). The insoluble format of MIPSOS protects protein components from degradation, while facilitating their sustained release. Proteomic analysis demonstrates that MIPSOS are highly enriched in pro-angiogenic factors, resulting in an enhanced pro-angiogenic bioactivity when compared to naïve MSC-derived ECM (cECM). Consequently, intravital microscopy of full-thickness skin wounds treated with MIPSOS demonstrates accelerated revascularization and healing, far superior to the therapeutic potential of cECM. Hence, the microparticle-based solidified stem cell secretome provides a promising platform to address major limitations of current therapeutic angiogenesis approaches.

HOIL‐1 ubiquitin ligase activity targets unbranched glucosaccharides and is required to prevent polyglucosan accumulation

HOIL‐1, a component of the linear ubiquitin chain assembly complex (LUBAC), ubiquitylates serine and threonine residues in proteins by esterification. Here, we report that mice expressing an E3 ligase‐inactive HOIL‐1[C458S] mutant accumulate polyglucosan in brain, heart and other organs, indicating that HOIL‐1’s E3 ligase activity is essential to prevent these toxic polysaccharide deposits from accumulating. We found that HOIL‐1 monoubiquitylates glycogen and α1:4‐linked maltoheptaose in vitro and identify the C6 hydroxyl moiety of glucose as the site of ester‐linked ubiquitylation. The monoubiquitylation of maltoheptaose was accelerated > 100‐fold by the interaction of Met1‐linked or Lys63‐linked ubiquitin oligomers with the RBR domain of HOIL‐1. HOIL‐1 also transferred pre‐formed ubiquitin oligomers to maltoheptaose en bloc, producing polyubiquitylated maltoheptaose in one catalytic step. The Sharpin and HOIP components of LUBAC, but not HOIL‐1, bound to unbranched and infrequently branched glucose polymers in vitro, but not to highly branched mammalian glycogen, suggesting a potential function in targeting HOIL‐1 to unbranched glucosaccharides in cells. We suggest that monoubiquitylation of unbranched glucosaccharides may initiate their removal from cells, preventing precipitation as polyglucosan.

Bacteria eat nanoprobes for aggregation-enhanced imaging and killing diverse microorganisms

Currently optical-based techniques for in vivo microbial population imaging are limited by low imaging depth and highly light-scattering tissue; and moreover, are generally effective against only one specific group of bacteria. Here, we introduce an imaging and therapy strategy, in which different bacteria actively eat the glucose polymer (GP)-modified gold nanoparticles through ATP-binding cassette (ABC) transporter pathway, followed by laser irradiation-mediated aggregation in the bacterial cells. As a result, the aggregates display ~15.2-fold enhancement in photoacoustic signals and ~3.0-fold enhancement in antibacterial rate compared with non-aggregated counterparts. Significantly, the developed strategy allows ultrasensitive imaging of bacteria in vivo as low ~105 colony-forming unit (CFU), which is around two orders of magnitude lower than most optical contrast agents. We further demonstrate the developed strategy enables the detection of ~107 CFU bacteria residing within tumour or gut. This technique enables visualization and treatment of diverse bacteria, setting the crucial step forward the study of microbial ecosystem.

The C-Terminal Domain of Liquorilactobacillus nagelii Dextransucrase Mediates the Production of Larger Dextrans Compared to Liquorilactobacillus hordei.

Dextransucrases released by certain lactic acid bacteria form glucose polymers with predominantly α-1,6-linkages and may be exploited biotechnologically for the tailored production of polysaccharides with application potential. Despite releasing two closely related dextransucrases, previous studies showed that water kefir borne Liquorilactobacillus (L.) hordei TMW 1.1822 and L. nagelii TMW 1.1827 produce different amounts of polysaccharides with distinct particle sizes (molecular weight and radius of gyration) and molecular architectures. To investigate where these differences originate and thus to provide deeper insights into the functionally diverse nature of polysaccharide formation during water kefir fermentation, we constructed two variants of the L. nagelii dextransucrase—a full-length enzyme and a truncated variant, devoid of a C-terminal glucan-binding domain that reflects the domain architecture of the L. hordei dextransucrase—and applied them at various enzyme concentrations to form dextran over 24 h. The full-length enzyme exhibited a high activity, forming constant amounts of dextran until a four-fold dilution, whereas the truncated variant showed a gradual decrease in activity and dextran formation at an increasing dilution. The application of the full-length enzyme resulted in higher average particle sizes compared to the truncated variant. However, the dilution of the enzyme extracts also led to a slight increase in the average particle size in both enzymes. Neither the domain architecture nor the enzyme concentration had an impact on the structural architecture of the dextrans. The presented results thus suggest that the comparatively higher processivity of the L. nagelii dextransucrase is predominantly caused by the additional C-terminal glucan-binding domain, which is absent in the L. hordei dextransucrase. The average particle size may be influenced, to some extent, by the applied reaction conditions, whereas the structural architecture of the dextrans is most likely caused by differences in the amino acid sequence of the catalytic domain.