Phage-driven coevolution reveals trade-off between antibiotic and phage resistance in Salmonella anatum.

Phage therapy faces challenges against multidrug-resistant (MDR) Salmonella due to rapid phage-resistant mutant emergence. Understanding the intricate interplay between antibiotics and phages is essential for shaping Salmonella evolution and advancing phage therapy. In this study, MDR Salmonella anatum (S. anatum) 2089b coevolved with phage JNwz02 for 30 passages (60 days), then the effect of coevolution on the trade-off between phage and antibiotic resistance in bacteria was investigated. Our results demonstrated antagonistic coevolution between bacteria and phages, transitioning from arms race dynamics (ARD) to fluctuating selection dynamics (FSD). The fitness cost of phage resistance, manifested as reduced competitiveness, was observed. Bacteria evolved phage resistance while simultaneously regaining sensitivity to amoxicillin, ampicillin, and gentamicin, influenced by phage selection pressure and bacterial competitiveness. Moreover, the impact of phage selection pressure on the trade-off between antibiotic and phage resistance was more pronounced in the ARD stage than in the FSD stage. Whole genome analysis revealed mutations in the btuB gene in evolved S. anatum strains, with a notably higher mutation frequency in the ARD stage compared to the FSD stage. Subsequent knockout experiments confirmed BtuB as a receptor for phage JNwz02, and the deletion of btuB resulted in reduced bacterial competitiveness. Additionally, the mutations identified in the phage-resistant strains were linked to multiple single nucleotide polymorphisms (SNPs) associated with membrane components. This correlation implies a potential role of these SNPs in reinstating antibiotic susceptibility. These findings significantly advance our understanding of phage-host interactions and the impact of bacterial adaptations on antibiotic resistance.

Fabrication of a high performance flexible capacitive porous GO/PDMS pressure sensor based on droplet microfluidic technology.

Porous structures are an effective way to improve the performance of flexible capacitive sensors, but the pore size uniformity of porous structures is not easily controlled by current methods, which may affect the inconsistent performance of different batches of sensors. In this paper, a high performance capacitive flexible porous GO/PDMS pressure sensor was prepared based on droplet microfluidic technology. By testing the performance of the sensor, we found that the sensor with a flow rate ratio of 1 : 3 has relatively good performance, with a degree of hysteresis (DH) of 8.64% and a coefficient of variation (CV) of 5.2%. Therefore, we studied the sensor performance based on this process. The result shows that the sensitivity of the flexible capacitive porous GO/PDMS pressure sensor reached 0.627 kPa-1 at low pressure (0-3 kPa), which is significantly higher than that of the pure PDMS thin film sensor (about 0.031 kPa-1) and the porous PDMS pressure sensor (0.263 kPa-1). At the same time, the sensor has a large range with a fast response time of 240 ms and a relaxation time of 300 ms at 30 kPa and an ultra-low detection limit (70 Pa). It can maintain stable operation under continuous force loading/unloading cycles and can respond well to different pressure step changes, so the sensor can be used to detect the movement process of each finger, knee, foot and other joints of the human body. In conclusion, the droplet microfluidic technology can effectively prepare high-performance capacitive flexible porous GO/PDMS pressure sensors.

Quantitative Risk Assessment of Five Foodborne Viruses in Shellfish Based on Multiplex qPCR.

Foodborne diseases are currently the most critical food safety issue in the world. There are not many hazard identification and exposure assessments for foodborne viruses (Norovirus GI, GII, Hepatitis A Virus, Rotavirus, Adenovirus) in shellfish. Multiplex qPCR for the simultaneous detection of five foodborne viruses was established and used to assess infection risk based on a 1-year pathogenesis study. The sensitivity, specificity and reproducibility of the multiplex qPCR method are consistent with that of conventional qPCR, which saves more time and effort. Overall, 37.86% of shellfish samples had one or more foodborne viruses. Risk assessment formulae and matrices were used to develop risk assessments for different age groups, different seasons and different shellfish. The annual probability of contracting a foodborne virus infection from shellfish is greater than 1.6 × 10-1 for all populations, and even for infants aged 0-4 years, it is greater than 1.5 × 10-2, which is much higher than the risk thresholds recommended by WHO (10-6) and the US EPA (10-4). High risk (level IV) is associated with springtime, and medium risk (level III) is associated with Mussel consumption. This study provides a basis for the risk of foodborne viral infections in people of different ages, in different seasons, and by consuming different shellfish.

Use of bentonite-coated activated carbon for improving the sensitivity of RT-qPCR detection of norovirus from vegetables and fruits: The ISO 15216-1:2017 standard method extension.

Produce-related foodborne outbreaks are becoming increasingly prevalent worldwide. In plant tissues, various compounds, including polysaccharides, phenolic compounds, and chlorophyll, can inhibit RT-PCR detection of viruses. In this study, we developed a highly sensitive RT-qPCR in combination with the bentonite-coated activated carbon (BCAC) assay for detection of norovirus from fruits and vegetables, which could be completed within 7 h and was about 10-100 fold more sensitive than the standard procedures (ISO 15216-1:2017). The extraction efficiencies of three surrogate viruses (MS2, MNV-1, and TV) from five fresh produce (lettuce, cherry tomato, blueberry, strawberry, and spinach) were higher with BCAC treatment than those of control groups, ranging from 17.82% to 98.60%. The average detection limit of these viruses using the BCAC-RT-qPCR method was stable at an average of 102 PFU/g or GC/g. Finally, this BCAC-RT-qPCR method was applied for detection of human norovirus GII.4 spiked onto lettuce and cherry tomato. The viral extraction efficiencies were up to 53.43% and 95.56%, respectively, which is almost four and seven times better than those without BCAC. Therefore, the BCAC-RT-qPCR method can be used to detect low levels of foodborne viruses from produce.

Soluble extracellular polymeric substance (SEPS) of histo-blood group antigen (HBGA) expressing bacterium Sphingobacterium sp. SC015 influences the survival and persistence of norovirus on lettuce.

Foodborne norovirus (NoV) outbreaks linked to leafy greens are common due to a lack of efficient strategies to prevent NoV spread from contaminated surfaces. We previously found that Sphingobacterium sp. SC015 in lettuce phyllosphere expresses histo-blood group antigen (HBGA)-like substances in soluble extracellular polymeric substances (SEPS) that contribute to NoV adherence on lettuce. Here, we extracted SEPS from bacterium SC015 (SEPS-SC015), analyzed their chemical composition, and examined their roles in the survival and protection of NoV and surrogates [murine norovirus (MNV-1) and Tulane virus (TuV)] on lettuce. Presence of SEPS-SC015 significantly increased survival and persistence of human NoV (HuNoV), MNV-1, and TuV at days 7 and 14, compared with virus alone. HuNoV, TuV, and MNV-1 seeded with SEPS-SC015 were more resistant to heat (70 °C, 2 min) than these viruses alone. SEPS-SC015 also increased viral resistance to sodium hypochlorite inactivation by treatment with 30 and 300 ppm bleach at 26 °C for 10 min. However, SEPS-SC015 was not effective at protecting these viruses under UV inactivation. Binding of TuV to SC015 bacteria and SEPS-SC015, visualized using transmission electron microscopy, suggests that protection might be related to direct interaction between SEPS-SC015 and viral particles. This study provides important insights that will help inform strategies to improve food safety.

Surveillance for foodborne disease outbreaks in Zhejiang Province, China, 2015-2020.

BACKGROUND: Foodborne diseases are a major cause of morbidity and mortality and a major public health problem worldwide. We aim to explore characteristics of foodborne disease outbreaks (FBDOs) in Zhejiang Province and to provide data support for foodborne disease prevention and control. To our knowledge, few such analyses have been published at the provincial level. METHODS: Descriptive statistical methods were used to analyze the data reported by centers for disease control (CDC) at all levels in Zhejiang Province through Foodborne Disease Outbreaks Surveillance System (FDOSS) during 2015-2020. RESULTS: A total of 962 FBDOs were reported during this period, resulting in 8324 illnesses, 1028 hospitalizations, and 20 deaths. The number of outbreaks (410 outbreaks, 42.62%) and cases (4991 cases, 59.96%) caused by bacteria were the largest, followed by poisonous mushrooms (157 outbreaks, 587 cases), which was the main cause of death (15 deaths, 75%). The highest number of FBDOs occurred in households (381 outbreaks, 39.60%), followed by restaurants (219 outbreaks, 22.77%) and canteens (174 outbreaks, 18.08%). Animal-based foods were the most common single food reported (232 outbreaks, 24.12%), followed by poisonous mushrooms (162 outbreaks, 16.84%), and plant-based foods (133 outbreaks, 13.83%). Poisonous mushrooms took the first place in outbreaks in households (38.32%, 146/381), while bacteria took the first place in outbreaks outside households. Vibrio parahaemolyticus was responsible for the largest number of outbreaks (232 outbreaks, 24.12%), which mainly occurred in catering service units (93.10%, 216/232). Different types of bacteria tended to be found in different food categories, such as Vibrio parahaemolyticus, which was mainly found in aquatic products. CONCLUSIONS: Analysis of FBDOs can provide insight into the most important pathogens and sources of foodborne disease, helping authorities identify high-risk etiologies, high-risk foods, and high-risk settings to guide policies that would reduce FBDOs.

Epidemiological analysis of wild mushroom poisoning in Zhejiang province, China, 2016-2018.

Wild mushroom poisoning has been recognized as a global problem threatening human health. In this study, we aimed to explore characteristics of wild mushroom poisoning in Zhejiang province, China. From 2016 to 2018, 429 cases of wild mushroom poisoning were reported, and among them, there were 2 deaths and 84 hospitalizations, with the incidence of 0.2526 per 100,000 and the case fatality rate of 0.47%. Digestive symptoms were found in all cases. Systemic symptoms and signs, neurological symptoms, and urinary symptoms were found in 28.90% (124/429), 11.66% (50/429), and 4.90% (21/429) of the cases, respectively. The proportion of cases with incubation period <6 h was 85.78%, and those with ≥6 h accounted for 14.22%. The peak period of poisoning occurred from June to October annually. Quzhou (Moran's I = 1.242, p < .05) and Lishui (Moran's I = 0.759, p < .05) with mild climate, more mountains, and abundant rainfall were "hot spots" for the incidence of wild mushroom poisoning, showing a state of high-incidence aggregation. Epidemiological analysis showed that there were seasonal, high-incidence areas and high-risk groups in wild mushroom poisoning. The government should give early warning to high-incidence areas and strengthen publicity to high-risk groups before wild mushrooms mature every summer and autumn. In addition, we recommend that ordinary people not pick wild mushrooms outdoors for consumption, because it is difficult to distinguish whether wild mushrooms are poisonous and do not buy wild mushrooms of unknown sources.

Protein degradation control and regulation of bacterial survival and pathogenicity: the role of protein degradation systems in bacteria.

BACKGROUND: Protein degradation systems play crucial roles in all the kingdoms of life. Their natural function is to eliminate proteins that are improperly synthesized, damaged, aggregated, or short-lived, ensuring the timely and accurate regulation of the response to abrupt environmental changes. Thus, proteolysis plays an important role in protein homeostasis, quality control, and the control of regulatory processes, such as adaptation and cell development. Except for the lysosome, ATPases Associated with various cellular Activities (AAA+) ATPase-protease complex is another major protein degradation system in the cell. METHODS AND RESULTS: The AAA+ ATPase-protease complex is a giant energy-dependent protease complex found in almost all kinds of cells, including bacteria, archaea and eukarya. Based on sequence analysis of ClpQ (HslV) and 20S proteasome beta subunits, it was found that bacterial ClpQ possess multiple same highly conserved motifs with 20S proteasome beta subunits of archaea and eukaryote. In this review, we also discussed the structure and functional mechanism, protein degradation signals and pathogenic role of proteasome / Clp protease complex in prokaryotes. CONCLUSION: Bacterial protein degradation systems play important roles in stress tolerance, protein quality control, DNA protection, transcription and pathogenicity of bacteria. But our current knowledge of the bacterial protease system is incomplete, and further research into the Clp protease complex and associated protein degradation signals will extend our understanding of the metabolism, physiology, reproduction, and pathogenicity of bacteria.

Effect of Direct Viral-Bacterial Interactions on the Removal of Norovirus From Lettuce.

Norovirus (NoV) is the main non-bacterial pathogen causing outbreaks of gastroenteritis and is considered to be the leading cause of foodborne illness. This study aims to determine whether lettuce-encapsulated bacteria can express histo-blood group antigen (HBGA)-like substances to bind to NoV and, if so, to explore its role in protecting NoV from disinfection practices. Fifteen bacterial strains (HBGA-SEBs) were isolated from the lettuce microbiome and studied as they were proved to have the ability to express HBGA-like substances through indirect ELISA detection. By using attachment assay, HBGA-SEBs showed great abilities in carrying NoVs regarding the evaluation of binding capacity, especially for the top four strains from genera Wautersiella, Sphingobacterium, and Brachybacterium, which could absorb more than 60% of free-flowing NoVs. Meanwhile, the direct viral-bacterial binding between HBGA-like substance-expressing bacteria (HBGA-SEB) and NoVs was observed by TEM. Subsequently, results of simulated environmental experiments showed that the binding of NoVs with HBGA-SEBs did have detrimental effects on NoV reduction, which were evident in short-time high-temperature treatment (90°C) and UV exposure. Finally, by considering the relative abundance of homologous microorganisms of HBGA-SEBs in the lettuce microbiome (ca. 36.49%) and the reduction of NoVs in the simulated environments, we suggested putting extra attention on the daily disinfection of foodborne-pathogen carriers to overcome the detrimental effects of direct viral-bacterial interactions on the reduction of NoVs.

Prevalence of ß-Lactam Drug-Resistance Genes in Escherichia coli Contaminating Ready-to-Eat Lettuce.

Thirty-four Escherichia coli isolates from 91 ready-to-eat lettuce packages, obtained from local supermarkets in Northern California, were genotyped by multilocus sequence typing, tested for susceptibility to antimicrobial agents, and screened for ß-lactamase genes. We found 15 distinct sequence types (STs). Six of these genotypes (ST1198, ST2625, ST2432, ST2819, ST4600, and ST5143) have been reported as pathogens found in human samples. Twenty-six (76%) E. coli isolates were resistant to ampicillin, 17 (50%) to ampicillin/sulbactam, 8 (23%) to cefoxitin, and 7 (20%) to cefuroxime. blaCTX-M was the most prevalent ß-lactamase gene, identified in eight (23%) isolates. We identified a class A broad-spectrum ß-lactamase SED-1 gene, blaSED, reported by others in Citrobacter sedlakii isolated from bile of a patient. This study found that fresh lettuce carries ß-lactam drug-resistant E. coli, which might serve as a reservoir for drug-resistance genes that could potentially be transmitted to pathogens that cause human infections.

Occurrence and risk assessment of 3- and 2-monochloropropanediol (MCPD) esters in vegetable oils and related products from Zhejiang market.

3- And 2-monochloropropanediol fatty acid esters (3- and 2-MCPD esters) are contaminants of processed vegetable oils. In this study, vegetable oils and related products available 486 food samples from Zhejiang market were collected and analysed for 3- and 2-MCPD esters during 2016-2018. Food consumption data were taken from a food consumption survey of urban and rural residents in Zhejiang province performed in 2008 using data from 9646 subjects. Levels of 3-MCPD esters in foods ranged from not detected to 8.3 mg/kg, and the highest mean levels were found in vegetable oils with levels of 0.76 mg/kg. Esters of 2-MCPD levels ranged from not detected to 4.0 mg/kg, and the highest mean levels were found in instant noodles containing 0.40 mg/kg. The dietary intake of 3-MCPD was 0.62 µg/kg bw per day (mean) and 2.29 µg/kg bw per day (P97.5), and 2-MCPD esters intakes were 0.26 µg/kg bw per day (mean) and 0.87 µg/kg bw per day (P97.5). Vegetable oils were the main food source of dietary 3- and 2-MCPD esters intake. These findings suggested that the dietary exposure levels of 3-MCPD esters may pose a potential risk to the health for high consumers (P97.5) aged 4-17 when compared to the tolerable daily intake.

Atomic-scale investigation of enhanced lithium, sodium and magnesium storage performance from defects in MoS2/graphene heterostructures.

MoS2 is of great interest as an anode material of batteries due to its high theoretical reversible capacity; in particular, a defective MoS2/graphene heterostructure exhibits excellent cycling stability. However, very little is known about the diffusion and ion storage mechanism at the atomistic level. To provide insights into the issue, we have developed and used first principles calculations and an atom intercalation/deintercalation algorithm to model the adsorption, diffusion, insertion and removal of Li, Na and Mg in pristine and defective MoS2/graphene systems. First, the adsorption of Li, Na and Mg is generally more stable in the defective MoS2/graphene structure. Mg and Li prefer to diffuse in the structure with disulfide defects, while Na prefers to diffuse in the molybdenum defective structure. Next, we found that the atomic configurations of both pristine and defective MoS2/graphene are not restored to their original states after the insertion and removal of Li, Na and Mg, which is related to the irreversible capacity loss of the system. Furthermore, by excluding the amount of lithium atoms related to the unrestored sulfur atoms, an algorithm was proposed to calculate the reversible capacity and it was verified by experimental results. We have also demonstrated that the introduction of defects leads to significant increase in the theoretical capacities of the Na and Mg systems, however, decreasing the capacity retention rate of Mg.

Culturable bacteria resident on lettuce might contribute to accumulation of human noroviruses.

Human noroviruses (HuNoVs) are the primary non-bacterial pathogens causing acute gastroenteritis worldwide. Attachment and invasion of HuNoVs are thought to involve histo-blood group antigens (HBGAs). Romaine lettuce, which is usually consumed raw, is a common food-related vehicle for HuNoVs transmission. This study investigated the possibility that bacteria resident on the surface of lettuce leaves contribute to norovirus adherence to this food. To test this hypothesis, bacteria were isolated from romaine lettuce and screened to evaluate whether they produced any polysaccharides with structures resembling HBGAs. Twenty-seven bacterial isolates were screened and 18, belonging to 13 different genera, were found to produce HBGAs-like polysaccharides that were recognized by monoclonal antibodies specific to type A, B, H and Lewis a, b, x and y. One bacterial isolate, belonging to the genus Pseudomonas was further investigated because it produced polysaccharides with the widest range of HBGA types, including type B, H and Lewis a, b and x. The Pseudomonas HBGAs-like polysaccharides were found to be extracellular and their production was enhanced when the bacteria were cultured in oligotrophic medium. HuNoVs capture assays revealed that GI.1, GI.8, and GII.2, GII.3, GII.4, GII.6, GII.12, GII.17 genotypes can be bind to Pseudomonas HBGAs-like polysaccharides. The direct evidence of bacterial production HBGAs-like polysaccharides demonstrates one possible mechanism driving accumulation of HuNoVs on lettuce.

Analysis of foodborne disease outbreaks in schools in Zhejiang Province during 2010-2019 / 中国学校卫生

Objective@#To understand the epidemiological characteristics of foodborne disease outbreaks in schools in Zhejiang province, and to provide evidence for effective prevention and control of foodborne disease outbreaks in schools.@*Methods@#A descriptive analysis was conducted on foodborne disease outbreaks in Zhejiang schools reported by the national foodborne disease outbreaks surveillance system from 2010 to 2019.@*Results@#During the past 10 years, a total of 86 foodborne disease outbreaks in schools were reported, with 1 755 illnesses, 240 hospitalizations, and no deaths. Pathogenic bacteria and their toxins were the main causes of foodborne disease outbreaks in schools, accounting for 83.0%(44/53) of all identified causes. The top four types of pathogenic bacteria were Staphylococcus aureus, Salmonella, diarrheagenic Escherichia coli, and Bacillus cereus. Meat products and mixed foods were the main foods that caused the outbreaks, each accounting for 16.3%(14/86) of total incidents. High school cafeterias were places with the highest incidence, accounting for 38.4%(33/86) of the total. School concession stands caused the largest number of hospitalizations, accounting for 37.1%(89/240) of the total. The peak month of foodborne disease outbreaks in schools was September, followed by June, May, and October. Crosscontamination and improper storage were the main causes of foodborne disease outbreaks in schools.@*Conclusion@#Bacterial foodborne disease is a major food safety issue in schools in Zhejiang Province. In summer and fall, school cafeterias and food stores should take effective measures to prevent bacterial foodborne disease outbreaks caused by cross-contamination and improper storage of high-risk foods such as meat products and cold-processed bakeries.

Antiviral Effects of Houttuynia cordata Polysaccharide Extract on Murine Norovirus-1 (MNV-1)-A Human Norovirus Surrogate.

Houttuynia cordata is an herbal plant rich in polysaccharides and with several pharmacological activities. Human noroviruses (HuNoVs) are the most common cause of foodborne viral gastroenteritis throughout the world. In this study, H. cordata polysaccharide (HP), with a molecular weight of ~43 kDa, was purified from H. cordata water extract (HWE). The polysaccharide HP was composed predominantly of galacturonic acid, galactose, glucose, and xylose in a molar ratio of 1.56:1.49:1.26:1.11. Methylation and NMR analyses revealed that HP was a pectin-like acidic polysaccharide mainly consisting of α-1,4-linked GalpA, ß-1,4-linked Galp, ß-1,4-linked Glcp, and ß-1,4-linked Xylp residues. To evaluate the antiviral activity of H. cordata extracts, we compared the anti-norovirus potential of HP with HWE and ethanol extract (HEE) from H. cordata by plaque assay (plaque forming units (PFU)/mL) for murine norovirus-1 (MNV-1), a surrogate of HuNoVs. Viruses at high (8.09 log10 PFU/mL) or low (4.38 log10 PFU/mL) counts were mixed with 100, 250, and 500 µg/mL of HP, HWE or HEE and incubated for 30 min at room temperature. H. cordata polysaccharide (HP) was more effective than HEE in reducing MNV-1 plaque formation, but less effective than HWE. When MNV-1 was treated with 500 µg/mL HP, the infectivity of MNV-1 decreased to an undetectable level. The selectivity indexes of each sample were 1.95 for HEE, 5.74 for HP, and 16.14 for HWE. The results of decimal reduction time and transmission electron microscopic revealed that HP has anti-viral effects by deforming and inflating virus particles, thereby inhibiting the penetration of viruses in target cells. These findings suggest that HP might have potential as an antiviral agent in the treatment of viral diseases.

Development of an analytical method for urocanic acid isomers in fish based on reactive extraction cleanup and chaotropic chromatography techniques.

Urocanic acid (UA), existing in trans- or cis-isoform, is of fairly recent interest to food researchers because of its potential public health hazards of scombrotoxicity and immunotoxicity, as well as associating with fish spoilage. This work is among the first efforts to study the analytical chemistry of UA in fish. With 0.6 M perchloric acid UA was extracted, and co-extracted fish matrix components were efficiently removed through a reactive extraction of UA. The optimum conditions for the reactive extraction, which allowed an 80% recovery of UA, were sample pH adjustment to 9, twice extractions with 32% (w/w) di (2-ethylhexyl) phosphate in hexanol, and a back-extraction with 0.1 M hydrochloric acid at 1:1 phase ratio. A chaotropic hexafluorophosphate salt was added to acidic water-acetonitrile mobile phases to improve the reversed-phase chromatography of UA, which otherwise was poorly retained. Optimum separation conditions were obtained for fish samples and enabled a fast (10 min), convenient-to-use chromatography that clearly outperforms cumbersome legacy ion-pair chromatography. Intended for routine use in our laboratory, the proposed method passed an in-house validation test for linearity, matrix effect (on reactive extraction), accuracy, precision, and detectability.

Evaluation of an Extraction Method for the Detection of GI and GII Noroviruses in Fruit and Vegetable Salads.

Human norovirus (HuNoV) is a major foodborne virus causing gastroenteritis outbreaks in humans. Salad products can be vectors of transmission for foodborne viruses such as HuNoV when these products are contaminated naturally or through unsanitary food handling. Therefore, development of simple, reliable and sensitive techniques for the detection of HuNoV in salad products is needed to ensure food safety. The purpose of our study was to optimize a method for the detection of HuNoV in artificially contaminated salad products. To this end, 2 different kinds of salads (fruit salads and vegetable salads) were experimentally inoculated with HuNoV GI, HuNoV GII, and MS2 suspensions. The selected method was based on treatment with pectinase followed by Trizol-chloroform purification, and the recovery efficiencies were 6.07% to 26.52% for HuNoV GI and 5.54% to 37.36% for HuNoV GII. MS2 was used as the process control, and the recovery efficiencies for fruit salad and vegetable salad samples were 38.57% and 41.13%, respectively. The optimized method could be applied in diagnostic laboratories to identify NoV contamination in composite foods, such as salad products, should an event of foodborne outbreak occur.

Large-scale molecular dynamics modeling of boron-doped amorphous SiCO ceramics.

At high temperature, silicon oxycarbide (SiCO) exhibits excellent mechanical properties and thermal stability. The incorporation of boron in SiCO results in improved performance in creep temperatures. In this work, large-scale molecular dynamics calculations were applied to obtain amorphous SiCO structures containing boron. Phase separation of C-C, B-C and Si-O was achieved for three compositions, and silicon-centered mixed-bond tetrahedrons were reproduced successfully. As the boron content increases, the boron atoms tend to form B-C and B-Si bonds in the voids, which stretches the free carbon network in some instances, causing a increase in C-C distance. Young's modulus remains stable at high temperature for the high-carbon case, which indicates that the free carbon network plays a critical role in the structural and thermal stability of SiBCO. Graphical Abstract Three major typical structures in the cooling down process for silicon boron oxycarbide (Si5BC2O8). Bonds: red Si-O, blue Si-C, black C-C, green B-C, purple Si-B.

In vitro fermentation behaviors of fucosylated chondroitin sulfate from Pearsonothuria graeffei by human gut microflora.

A fucosylated chondroitin sulfate (FCS-pg) with highly repeated structure from Pearsonothuria graeffei was subjected to a in vitro fermentation model to investigate its fermentability and effects on human gut microflora. High performance liquid chromatography (HPLC) measurement found FCS-pg can be fermented to short chain fatty acids (SCFAs) by gut microflora from partial human fecal samples. 16S rRNA gene-based polymerase chain reaction-based denaturing gradient gel electrophoresis (PCR-DGGE) profiling and real-time quantitative PCR analysis showed that FCS-pg mainly increased the proportions of Clostridium cluster XI, Bacteriodes prevotella group, Bifidobacterium genus, Clostridium cluster I and Clostridium cluster XIVab, whereas the numbers of the Enterobacteriaceae and Lactobacillus decreased. These results indicated that FCS-pg was mainly fermented by Bacteroides, Bifidobacterium and Clostridium. It increased the content of probiotics bacteria in achieving health-enhancing effect, was slightly different than most sulfated polysaccharides from marine animals. The current study provides useful new information on the mechanism of absorption and functional activity on FCS-pg within the gastrointestinal tract of the human body.

A Novel Polysaccharide Conjugate from Bullacta exarata Induces G1-Phase Arrest and Apoptosis in Human Hepatocellular Carcinoma HepG2 Cells.

Bullacta exarata has been consumed in Asia, not only as a part of the normal diet, but also as a traditional Chinese medicine with liver- and kidney-benefitting functions. Several scientific investigations involving extraction of biomolecules from this mollusk and pharmacological studies on their biological activities have been carried out. However, little is known regarding the antitumor properties of polysaccharides from B. exarata, hence the polysaccharides from B. exarata have been investigated here. One polysaccharide conjugate BEPS-IA was isolated and purified from B. exarata. It mainly consisted of mannose and glucose in a molar ratio of 1:2, with an average molecular weight of 127 kDa. Thirteen general amino acids were identified to be components of the protein-bound polysaccharide. Methylation and NMR studies revealed that BEPS-IA is a heteropolysaccharide consisting of 1,4-linked-α-d-Glc, 1,6-linked-α-d-Man, 1,3,6-linked-α-d-Man, and 1-linked-α-d-Man residue, in a molar ratio of 6:1:1:1. In order to test the antitumor activity of BEPS-IA, we investigated its effect against the growth of human hepatocellular carcinoma cells HepG2 in vitro. The result showed that BEPS-IA dose-dependently exhibited an effective HepG2 cells growth inhibition with an IC50 of 112.4 µg/mL. Flow cytometry analysis showed that BEPS-IA increased the populations of both apoptotic sub-G1 and G1 phase. The result obtained from TUNEL assay corroborated apoptosis which was shown in flow cytometry. Western blot analysis suggested that BEPS-IA induced apoptosis and growth inhibition were associated with up-regulation of p53, p21 and Bax, down-regulation of Bcl-2. These findings suggest that BEPS-IA may serve as a potential novel dietary agent for hepatocellular carcinoma.