Heavy Metal-Induced Assembly of DNA Network Biosensor from Double-Loop Hairpin Probes for Ultrasensitive Detection of UO22+ in Water and Soil Samples.

The uranyl ion (UO22+) is the most stable form of uranium, which exhibits high toxicity and bioavailability posing a severe risk to human health. The construction of ultrasensitive, reliable, and robust sensing techniques for UO22+ detection in water and soil samples remains a challenge. Herein, a DNA network biosensor was fabricated for UO22+ detection using DNAzyme as the heavy metal recognition element and double-loop hairpin probes as DNA assembly materials. UO22+-activated specific cleavage of the DNAzyme will liberate the triggered DNA fragment, which can be utilized to launch a double-loop hairpin probe assembly among Hab, Hbc, and Hca. Through multiple cyclic cross-hybridization reactions, hexagonal DNA duplex nanostructures (n[Hab•Hbc•Hca]) were formed. This DNA network sensing system generates a high fluorescence response for UO22+ monitoring. The biosensor is ultrasensitive, with a detection limit of 2 pM. This sensing system also displays an excellent selectivity and robustness, enabling the DNA network biosensor to work even in complex water and soil samples with excellent accuracy and reliability. With the advantages of enzyme-free operation, outstanding specificity, and high sensitivity, our proposed DNA network biosensor provides a reliable, simple, and robust method for trace levels of UO22+ detection in environmental samples.

A Laboratory Experimental Study on Enhancing the Oil Recovery Mechanisms of Polymeric Surfactants.

In order to evaluate the physical and chemical properties of polymer surfactants and analyze their oil displacement mechanisms, three types of poly-surfactant used in the Daqing oil field were chosen to be researched, and the oil displacement effects were studied using poly-surfactants of different viscosity, dehydrating rate, and core permeability. The main purpose is to determine the reasonable range of different characteristic indexes of polymeric surfactant flooding. The oil displacement effect of 15 cores was analyzed, and the effects of viscosity, the dehydrating rate of emulsion, and permeability on EOR (Enhanced Oil Recovery) were analyzed. The oil displacement mechanisms of polymeric surfactants were researched using a photolithographic glass core. This paper explores the mechanism underlying production enhancement as an EOR target, while simultaneously conducting laboratory tests to assess the physical and chemical properties of polymeric surfactants. The poly-surfactant agents exhibit a notable increase in viscosity, with the optimal displacement effect observed at a core effective permeability exceeding 400 mD, resulting in a potential EOR of 15% or higher. Moreover, at a viscosity ranging between 40 and 70 mPa·s, the total EOR can reach 73%, with the peak efficiency occurring at a viscosity of 60 mPa·s. The water loss rate of the emulsion, ranging between 30% and 70%, achieves optimal performance at 50%. The poly-surfactants' higher viscosity extends the oil sweep area, enhancing recovery efficiency, and noticeably reducing residual oil compared to water flooding. During poly-surfactant flooding, a substantial amount of residual oil is extracted and transformed into droplets. The rapid emulsification of the polymeric surfactant solution with crude oil forms a stable emulsion, contributing to its significant oil recovery effect. This research provides valuable technical support for EOR in thin and low-quality reservoirs of onshore multi-layered sandstone reservoirs.

Generation and application of a monoclonal antibody against the 18-kDa oncosphere antigen of Taenia pisiformis.

Taenia pisiformis is a parasite that causes cysticercosis pisiformis, which has acquired economic relevance because of its effects on animal welfare and production. A useful assay for the detection of T. pisiformis is needed for the prevention of cysticercosis pisiformis and control of the parasite. The 18-kDa oncosphere antigen is expressed in the oncosphere of several cysticerci in species of the genus Taenia, including T. pisiformis. This protein plays an important role in tissue invasion and has extensive applications in diagnosis. In this study, the T. pisiformis 18-kDa oncosphere antigen (TPO18) was expressed in soluble form and successfully purified for use in the production of monoclonal antibodies (MAbs) against TPO18. Twenty hybridomas were obtained using ELISA, and the subcloning process identified three positive hybridoma cell lines, which were designated as 4E8, 5G5, and 7E8. MAb 7E8 exhibited the highest titer and had an IgG2b heavy chain and a kappa light chain. Western blot analysis demonstrated that MAb 7E8 reacted with GST-TPO18. Immunohistochemistry showed that TPO18 was widely distributed in the drape and wall of uteri in adults of T. pisiformis adults and in the fibrous layer of the sucker and cyst cavity of T. pisiformis cysticerci. This research will provide a foundation for the development of diagnostic tools and will contribute to a better understanding of the functions of TPO18.

Coxiella burnetii is widespread in ticks (Ixodidae) in the Xinjiang areas of China.

BACKGROUND: The gram-negative Coxiella burnetii bacterium is the pathogen that causes Q fever. The bacterium is transmitted to animals via ticks, and manure, air, dead infected animals, etc. and can cause infection in domestic animals, wild animals, and humans. Xinjiang, the provincial-level administrative region with the largest land area in China, has many endemic tick species. The infection rate of C. burnetii in ticks in Xinjiang border areas has not been studied in detail. RESULTS: For the current study, 1507 ticks were collected from livestock at 22 sampling sites in ten border regions of the Xinjiang Uygur Autonomous region from 2018 to 2019. C. burnetii was detected in 205/348 (58.91%) Dermacentor nuttalli; in 110/146 (75.34%) D. pavlovskyi; in 66/80 (82.50%) D. silvarum; in 15/32 (46.90%) D. niveus; in 28/132 (21.21%) Hyalomma rufipes; in 24/25 (96.00%) H. anatolicum; in 219/312 (70.19%) H. asiaticum; in 252/338 (74.56%) Rhipicephalus sanguineus; and in 54/92 (58.70%) Haemaphysalis punctata. Among these samples, C. burnetii was detected in D. pavlovskyi for the first time. The infection rate of Rhipicephalus was 74.56% (252/338), which was the highest among the four tick genera sampled, whereas the infection rate of H. anatolicum was 96% (24/25), which was the highest among the nine tick species sampled. A sequence analysis indicated that 63 16S rRNA sequences could be found in four newly established genotypes: MT498683.1 (n = 18), MT498684.1 (n = 33), MT498685.1 (n = 6), and MT498686.1 (n = 6). CONCLUSIONS: This study indicates that MT498684.1 might represent the main C. burnetii genotype in the ticks in Xinjiang because it was detected in eight of the tick species studied. The high infection rate of C. burnetii detected in the ticks found in domestic animals may indicate a high likelihood of Q fever infection in both domestic animals and humans.

Ultrasound-assisted extraction extracts from Stemona japonica (Blume) Miq. and Cnidium monnieri (L.) Cuss. could be used as potential Rhipicephalus sanguineus control agents.

Nicotiana tabacum, Stemona japonica, and Cnidium monnieri are common plants that are widely used for their anti-parasitic properties. The purpose of this study was to evaluate the acaricidal activity of extracts from these plants against the brown dog tick, Rhipicephalus sanguineus. A composition analysis of crude extracts by GC-MS was conducted to discover compounds with acaricidal effects. The toxicity of extraction against the engorged nymphs of R. sanguineus was evaluated by an immersion test. The results showed that the crude extracts of S. japonica and C. monnieri in varying ratios, concentrations, and from different extraction methods, had a killing effect on R. sanguineus. Lethality reached 76.67% ± 0.04410 when using a 1:1 extract of S. japonica:C. monnieri in 75% ethanol with ultrasonic extraction; the crude extract was determined at a concentration of 0.5 g/mL. GC-MS results showed that osthole and 5-hydroxymethylfurfural (5-HMF) are the main components of the extract. These results suggested that ultrasound-assisted extraction (UAE) extracts contained acaricidal components acting against R. sanguineus, which may result in the development of effective extracts of S. japonica and C. monnieri as a source of low-toxicity, plant-based, natural acaricidal drugs.

Sulfamic and succinic acid derivatives of 25-OH-PPD and their activities to MCF-7, A-549, HCT-116, and BGC-823 cell lines.

In the search for new anti-tumor agents with higher potency than our previously identified compound 1 (25-OH-PPD, 25-hydroxyprotopanaxadiol), 12 novel sulfamic and succinic acid derivatives that could improve water solubility and contribute to good drug potency and pharmacokinetic profiles were designed and synthesized. Their in vitro anti-tumor activities in MCF-7, A-549, HCT-116, and BGC-823 cell lines and one normal cell line were tested by standard MTT assay. Results showed that compared with compound 1, compounds 2, 3, and 7 exhibited higher cytotoxic activity on A-549 and BGC-823 cell lines, together with lower toxicity in the normal cell. In particular, compound 2 exhibited the best anti-tumor activity in the in vitro assays, which may provide valuable data for the research and development of new anti-tumor agents.

Bacillus nitroreducens sp. nov., a humus-reducing bacterium isolated from a compost.

A Gram-staining-positive, facultative anaerobic, motile and rod-shaped bacterium, designated GSS08(T), was isolated from a windrow compost pile and characterized by means of a polyphasic approach. Growth occurred with 0-4 % (w/v) NaCl (optimum 1 %), at pH 6.5-9.5 (optimum pH 7.5) and at 20-45 °C (optimum 37 °C). Anaerobic growth occurred with anthraquinone-2,6-disulphonate, fumarate and NO3 (-) as electron acceptor. The main respiratory quinone was MK-7. The predominant polar lipids were diphosphatidylglycerol and phosphatidylethanolamine. The major fatty acids (>5 %) were iso-C15:0 (43.1 %), anteiso-C15:0 (27.4 %) and iso-C16:0 (8.3 %). The DNA G + C content was 39.6 mol%. The phylogenetic analysis based on 16S rRNA gene sequences revealed that strain GSS08(T) formed a phyletic lineage with the type strain of Bacillus humi DSM 16318(T) with a high sequence similarity of 97.5 %, but it displayed low sequence similarity with other valid species in the genus Bacillus (<96.0 %). The DNA-DNA relatedness between strains GSS08(T) and B. humi DSM 16318(T) was 50.8 %. The results of phenotypic, chemotaxonomic and genotypic analyses clearly indicated that strain GSS08(T) represents a novel species, for which the name Bacillus nitroreducens sp. nov. is proposed. The type strain is GSS08(T) (=KCTC 33699(T) = MCCC 1K01091(T)).

Desulfotomaculum ferrireducens sp. nov., a moderately thermophilic sulfate-reducing and dissimilatory Fe(III)-reducing bacterium isolated from compost.

A novel dissimilatory Fe(III)-reducing bacterium, designated strain GSS09T, was isolated from a compost sample by using a solid medium containing acetate and ferrihydrite as electron donor and electron acceptor, respectively. Cells of strain GSS09T were anaerobic, Gram-stain-positive, motile, endospore-forming and rod-shaped. Growth occurred at 30-55 °C (optimum 50 °C), at pH 6.5-9.0 (optimum pH 7.5) and in the presence of 0-3 % (w/v) NaCl (optimum 1 %). Both sulfur compounds such as sulfate, sulfite and thiosulfate and Fe(III) oxides such as ferrihydrite could be utilized as electron acceptors. Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain GSS09T was related closely to Desulfotomaculum hydrothermale Lam5T (94.5 % sequence similarity). The major fatty acids were C16 : 0 and C16 : 1ω7c/C16 : 1ω6c. The G+C content of the genomic DNA was 49.1 mol%. On the basis of phylogenetic analysis, phenotypic characterization and physiological tests, strain GSS09T is considered to represent a novel species of the genus Desulfotomaculum, for which the name Desulfotomaculum ferrireducens sp. nov. is proposed. The type strain is GSS09T (=KCTC 15523T=MCCC 1K01254T).

Synthesis of novel 25-hydroxyprotopanaxadiol derivatives by methylation and methoxycarbonylation using dimethyl carbonate as a environment-friendly reagent and their anti-tumor evaluation.

A previous study involving 25-hydroxyprotopanaxadiol (25-OH-PPD) illustrated that the anti-cancer activity increased by 1-3 times after C-3/C-12-OH was substituted by short-chain fatty acids. In addition, 25-OCH3-PPD was also one of our research interests; the unique difference in structure between 25-OH-PPD and 25-OCH3-PPD is that in C-25, the latter activity was 2-5 times higher than that of 25-OH-PPD. These data serves as the scientific basis of our continuing research. To further confirm the effect of short chain acylated and methylated products on the activity and to identify more potent, higher selectivity compounds, we modified 25-OH-PPD with a green environment-friendly and non-toxic chemical dimethyl carbonate (DMC), which plays the role of both solvent and reagent. This experiment yielded 14 derivatives. Their in vitro anti-tumor activities were tested on two different human tumor cell lines (HeLa and DU145) and one normal cell line (IOSE144) by standard MTT assay. The results showed that compounds 3, 5, 6, 10, 11, 12, and 13 exhibited higher cytotoxic activity on two cell lines, with IC50 values within the range of 1.1-12µM. Compounds 12 and 13 exhibited the highest potent activity, with IC50 values of 1.1 and 1.2µM, respectively, on HeLa cells. Antitumor activity significantly increased after the hydroxyl groups are substituted by methyl. The results of the present study may provide useful data for evaluating the structure-activity relationships of other dammarane-type sapogenins and developing new antitumor agents.

The toxic effects of indoor atmospheric fine particulate matter collected from allergic and non-allergic families in Wuhan on mouse peritoneal macrophages.

Recent studies have shown that fine particulate matter (PM2.5) is associated with multiple adverse health outcomes and PM2.5-induced oxidative stress is now commonly known as a proposed mechanism of PM2.5-mediated toxicity. However, the association between allergic symptoms in children and exposure to PM2.5 has not been fully elucidated, particularly the role of PM2.5 on the indoor environment involved in allergy or non-allergy is unknown. The aim of the present study was to explore whether indoor PM2.5 from the homes of children with allergic symptoms had more increased risks of allergy than that of healthy ones and then compare the toxicity and inflammatory response of them. In this study, indoor PM2.5 was collected from the homes of schoolchildren with allergic symptoms and those of healthy ones respectively, and components of PM2.5 were analyzed. PM2.5-mediated oxidative damage and inflammatory response were further evaluated in mouse peritoneal macrophages based on its effects on the levels of reactive oxygen species accumulation, lipid peroxidation, DNA damage or cytokine production. It seems that oxidative stress may contribute to PM2.5-induced toxicity, and PM2.5 from the allergic indoor environment produced more serious toxic effects and an inflammatory response on mouse peritoneal macrophages than that from a non-allergic indoor environment.

Preliminary investigation of the influence of CREB1 gene polymorphisms on cognitive dysfunction in Chinese patients with major depression.

Research has increasingly focused on the role of the cyclic adenosine monophosphate (cAMP) response element binding (CREB) protein in learning and memory, particularly its role in cognitive disorders and neurodegeneration, such as Huntington's disease, Alzheimer's disease, Rubinstein-Taybi syndrome, and Coffin-Lowry syndrome. The cognitive dysfunction of patients with major depressive disorder (MDD), which is widely recognized, is not completely in accordance with depressive severity, and the dysfunction persists upon clinical remission in some patients. However, few studies have focused on the role of CREB on cognitive function in patients with MDD. This study aimed to investigate the influence of CREB1 polymorphism on cognitive function in patients with MDD. The current study comprised 113 patients with MDD. The severity of depression was measured using the 17-item Hamilton Depression Rating Scale, and cognitive function was assessed using the Stroop Neuropsychological Screening Test, verbal fluency test, and tests of immediate logical memory and visual reproduction. All subjects were genotyped with regard to CREB1 polymorphisms (rs10932201, rs2551645, rs2254137, rs6740584, and rs2551640). For the verbal fluency test, the results showed significant differences for all single-nucleotide polymorphism genotypic groups. For the Stroop color-word task, a significant difference was found only for rs6740584. No significant differences were found for the Stroop color task, the immediate logical memory test or the visual reproduction test. In conclusion, there was an effect of CREB1 polymorphism on selective attention and retrieval of long-term memory, but not on immediate memory.

Wearable Motion Analysis System for Thoracic Spine Mobility With Inertial Sensors.

This study presents a wireless wearable portable system designed for the automatic quantitative spatio-temporal analysis of continuous thoracic spine motion across various planes and degrees of freedom (DOF). This includes automatic motion segmentation, computation of the range of motion (ROM) for six distinct thoracic spine movements across three planes, tracking of motion completion cycles, and visualization of both primary and coupled thoracic spine motions. To validate the system, this study employed an Inter-days experimental setting to conduct experiments involving a total of 957 thoracic spine movements, with participation from two representatives of varying age and gender. The reliability of the proposed system was assessed using the Intraclass Correlation Coefficient (ICC) and Standard Error of Measurement (SEM). The experimental results demonstrated strong ICC values for various thoracic spine movements across different planes, ranging from 0.774 to 0.918, with an average of 0.85. The SEM values ranged from 0.64° to 4.03°, with an average of 1.93°. Additionally, we successfully conducted an assessment of thoracic spine mobility in a stroke rehabilitation patient using the system. This illustrates the feasibility of the system for actively analyzing thoracic spine mobility, offering an effective technological means for non-invasive research on thoracic spine activity during continuous movement states.

Fluoxetin suppresses tau phosphorylation and modulates the interaction between tau and tubulin in the hippocampus of CUMS rats.

Depression is considered a crucial psychiatric disease correlated with neuronal-dysfunctions induced by stress-stimuli. This study aimed to investigate effect of Fluoxetine (FL) on chronic unpredictable mild stress (CUMS) and explore the associated mechanisms. CUMS rat model was established by treating with lots of stresses. CUMS rats were administered FL, SB216763 (SB), Wortmannin (WT) alone or in combination. CUMS rats were administered 1 % sugar water to conduct sugar water consumption experiment. Acet-Tub, Tyr-Tub, tau46, p-tau-Ser199/202, p-tau-Ser396, p-tau-Ser231, expression was examined using immunohistochemical assay and western blotassay. Interaction between tau and tubulin was evaluated with immunoprecipitation assay. Double immunohistochemical assay was used to identify interaction between Nestin and Tau. The results indicated that FL treatment only increased sugar consumption of CUMS rats (P < 0.05), but also strengthened effects of SB and WT. FL significantly treatment decreased tau phosphorylation (p-tau) in hippocampal tissues of rats compared to those of rats in CUMS group (P < 0.05). FL treatment markedly decreased Acet-Tub and increased Tyr-Tub expression in hippocampal tissues of rats compared to those of rats in CUMS group (P < 0.05). The effects of FL treatment on p-tau down-regulation and tubulin modulation in hippocampal tissues were independent from PI3K and GSK-3 signaling pathways. FL treatment could also enhance proliferation and total tau of newborn neurons of CUMS rats. FL treatment strengthened interaction between tau and botulin in hippocampal tissues of CUMS rats. In conclusion, Fluoxetin suppressed phosphorylation of tau and modulated the interaction between tau and tubulin in hippocampus of adult CUMS rats.

Spatio-temporal variation of toxin-producing gene abundance in Microcystis aeruginosa from Poyang Lake.

Microcystis aeruginosa (M. aeruginosa) causes massive blooms in eutrophic freshwater and releases microcystin. Poyang Lake is the largest freshwater lake in China and has kept a mid-nutrient level in recent years. However, there is little research on microcystin production in Poyang Lake. In this study, water and sediment samples from ten sampling sites in Poyang Lake were collected from May to December in 2020, and from January to April in 2021 respectively. Microcystis genes (mcyA, mcyB, 16 s rDNA) were quantified by real-time fluorescence quantitative PCR analysis, and then the spatial and temporal variation of mcy genes, physicochemical factors, and bacterial population structure in the lake was analyzed. The relationship between the abundance of mcy genes and physicochemical factors in water column was also revealed. Results indicated that the microcystin-producing genes mcyA and mcyB showed significant differences in spatial and temporal levels as well, which is closely related to the physicochemical factors especially the water temperature (p < 0.05) and the nitrogen content (p < 0.05). The abundance of mcy genes in the sediment in December affected the abundance of mcy genes in the water column in the next year, while the toxic Microcystis would accumulate in the sediment. In addition to the toxic Microcystis, we also found a large number of non-toxic Microcystis in the water column and sediment, and the ratio of toxic to non-toxic species can also affect the toxicity production of M. aeruginosa. Overall, the results showed that M. aeruginosa toxin-producing genes in Poyang Lake distributed spatially and temporally which related to the physicochemical factors of Poyang Lake.

Postinterventional Petechial Hemorrhage Associated With Poor Functional Outcome After Successful Recanalization Following Endovascular Therapy.

BACKGROUND AND OBJECTIVES: Endovascular therapy (EVT) has emerged as the standard for treating patients with acute ischemic stroke due to large vessel occlusion. The aim of this study was to investigate the relationship between early petechial hemorrhage and patient outcomes after successful EVT of anterior circulation. METHODS: We retrospectively analyzed multicenter data from 316 patients who underwent EVT for acute occlusion of anterior circulation. Patients were divided into petechial hemorrhage group and without hemorrhage group based on post-EVT head imaging. Logistical regression analysis was performed to determine independent predictors for petechial hemorrhage, and for petechial hemorrhage as a predictor of early neurological improvement, favorable outcome at 90 days (modified Rankin Scale 0-2), and 90-day mortality, with adjustment for all factors significantly associated with these endpoints in univariate regression to P < .10. RESULTS: Of 316 included patients with successful EVT, 49 (15.50%) had petechial hemorrhage. The petechial hemorrhage group showed less early neurological improvement (36.73% compared with 53.56%, P = .030), less favorable outcomes at 90 days (32.65% compared with 61.80%, P < .001, absolute risk difference 29.15%), and higher mortality at 90 days (28.57% compared with 10.49%, P = .001) then the group without hemorrhage. Petechial hemorrhage was inversely associated with favorable 90-day outcome (odds ratio = 0.415, 95% CI 0.206-0.835) and higher mortality rate at 90 days (odds ratio = 2.537, 95% CI 1.142-5.635) in multivariable regression but was not independently associated with early neurological improvement. CONCLUSION: In patients with anterior large vessel occlusion who underwent successful EVT, petechial hemorrhage was associated with poor functional outcome and 90-day mortality when adjusted for complete recanalization, pre-EVT National Institute of Health Stroke Scale/Score, and Alberta Stroke Program Early Computed Tomography Score. Despite the relatively lower rate of a favorable 90-day outcome with petechial hemorrhage compared with no petechial hemorrhage, the absolute rate of a favorable outcome exceeds the natural history of medical management for this condition.

The effects of external cues on cross-border e-commerce product sales: An application of the elaboration likelihood model.

In response to the soaring demand for imported goods among Chinese consumers, this study innovatively investigates the role of external cues on consumer behavior on cross-border e-commerce platforms, utilizing advanced data crawling techniques to extract data from Tmall Global. Guided by the Elaboration Likelihood Model, this research unveils key determinants affecting consumer purchasing decisions, contributing novel insights to e-commerce literature and methodologies. Our analysis discovers that increased picture comments significantly boost sales and that source credibility, product collections, and price discounts also play pivotal roles, especially for experiential products. We further explore a nuanced, inverted U-shaped relationship between product title length and sales, offering a foundational understanding of non-linear relationships in consumer behavior and presenting practical implications for enhancing marketing strategies. This study, while acknowledging limitations like data access constraints, provides strategic insights into optimizing product information presentation and broadens understanding of consumer decision-making processes, thus adding substantial value to ongoing e-commerce discourse.

Continuous-Flow Microwave Milk Sterilisation System Based on a Coaxial Slot Radiator.

Microwave continuous-flow liquid food sterilisation, in which the liquid is mainly heated by microwaves, has the advantages of fast sterilisation speed, energy saving, comprehensive elimination, and less nutrient loss. Circular pipes are commonly used in microwave continuous-flow liquid heating processing. However, with circular pipes, which are widely used in the industry, the heating is uneven owing to the phenomenon of tube focusing when adopting external radiation. In this study, a novel microwave continuous-flow milk sterilisation system based on a coaxial slot radiator is proposed. First, the coaxial slot radiator was designed to realise efficient radiation through the establishment of multi-physics model. The structure of the system was then optimised by comparing the heating efficiency and uniformity of simulation results. The effect of microwave coaxial slot radiator rotation on heating uniformity was simulated and the results show that the heating uniformity is improved obviously. Experimental equipment was set up to verify the results of the simulation. The experimental results are consistent with the simulation results. Finally, the sensitivity analysis of the system is performed to confirm that, when the dielectric properties and types of liquid food change, the heating of the proposed microwave continuous-flow system remains efficient and uniform.

Molecular mechanism of lipopolysaccharide (LPS) in promoting biomineralization on bacterial surface.

Biomineralization on bacterial surface is affected by biomolecules of bacterial cell surface. Lipopolysaccharide (LPS) is the main and outermost component on the extracellular membrane of Gram-negative bacteria. In the present study, the molecular mechanism of LPS in affecting biomineralization of Ag+/Cl- colloids was investigated by taking advantages of two LPS structural deficient mutants of Escherichia coli. The two mutants were generated by impairing the expression of waaP or wbbH genes with CRISPR/Cas9 technology and it induced deficient polysaccharide chain of O-antigen (ΔwbbH) or phosphate groups of core oligosaccharide (ΔwaaP) in LPS structures. There were significant changes of the cell morphology and surface charge of the two mutants in comparing with that of wild type cells. LPS from ΔwaaP mutant showed increased ΔHITC upon interacting with free Ag+ ions than LPS from wild type cells or ΔwbbH mutant, implying the binding affinity of LPS to Ag+ ions is affected by the phosphate groups in core oligosaccharide. LPS from ΔwbbH mutant showed decreased endotherm (ΔQ) upon interacting with Ag+/Cl- colloids than LPS from wild type or ΔwaaP mutant cells, implying LPS polysaccharide chain structure is critical for stabilizing Ag+/Cl- colloids. Biomineralization of Ag+/Cl- colloids on ΔwbbH mutant cell surface showed distinctive morphology in comparison with that of wild type or ΔwaaP mutant cells, which confirmed the critical role of O-antigen of LPS in biomineralization. The present work provided molecular evidence of the relationship between LPS structure, ions, and ionic colloids in biomineralization on bacterial cell surface.

Lipopolysaccharide-stabilized ionic colloids induce biomineralization.

Biomineralization inducing by bacteria is common in nature. It involves interactions between bacterial surface and metal ions that are usually present in the form of ionic colloids. Lipopolysaccharide (LPS) is the major component of Gram-negative bacterial surfaces. In the present study, interactions between LPS and metal ions (Ag+, Fe3+, Cd2+, Co2+, Cu2+, Mn2+, Ni2+), as well as ionic colloids (Ag+/Cl-, Fe3+/OH-) were evaluated by means of isothermal titration calorimetry and Zeta potential measurement. It was found that LPS increases the energy barrier for the collapse of ionic colloids and prevents ionic colloids from aggregation. The roles of LPS-stabilized ionic colloids in inducing biomineralization on the bacterial surface were explored by means of scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray Diffraction. It showed that reducing colloidal stability by increasing the ionic strength significantly inhibited biomineralization of ionic colloids on bacterial surfaces. While the formation of ionic colloids promoted biomineralization on bacterial surfaces. This study provides a novel insight into biomineralization as well as biomineralization-based techniques with biological stabilizers for producing biominerals.

Functional Immobilization of a Biofilm-Releasing Glycoside Hydrolase Dispersin B on Magnetic Nanoparticles.

Dispersin B (DspB) is a member of glycoside hydrolase family 20 (GH20) and catalyzes degradation of biofilms forming by pathogenic bacteria such as Staphylococcus aureus. Magnetoreceptor (MagR) is a magnetic protein that can be used as a fusion partner for functionally immobilizing proteins on magnetic surfaces. In the present study, a recombinant protein DspB-MagR was constructed by fusing MagR to the C-terminus of DspB and expressed in Escherichia coli. Magnetic immobilization of purified DspB-MagR on magnetic core-shell structured Fe3O4@SiO2 nanoparticles was achieved and characterized by means of various techniques including SDS-PAGE, Fourier transform infrared spectroscopy, thermogravimetric analysis, zeta potential measurement, and scanning electron microscopy. It was evaluated the influence of temperature, pH, and storage time on the performance of immobilized DspB-MagR on Fe3O4@SiO2 nanoparticles. Removal of biofilms forming by Staphylococcus aureus and other medical sourced bacterial species was achieved by using Fe3O4@SiO2 nanoparticles loading with DspB-MagR. This work promoted potential applications of DspB and similar enzymes for medical purposes.