Microbial species pool-mediated diazotrophic community assembly in crop microbiomes during plant development.

Plant-associated diazotrophs strongly relate to plant nitrogen (N) supply and growth. However, our knowledge of diazotrophic community assembly and microbial N metabolism in plant microbiomes is largely limited. Here we examined the assembly and temporal dynamics of diazotrophic communities across multiple compartments (soils, epiphytic and endophytic niches of root and leaf, and grain) of three cereal crops (maize, wheat, and barley) and identified the potential N-cycling pathways in phylloplane microbiomes. Our results demonstrated that the microbial species pool, influenced by site-specific environmental factors (e.g., edaphic factors), had a stronger effect than host selection (i.e., plant species and developmental stage) in shaping diazotrophic communities across the soil-plant continuum. Crop diazotrophic communities were dominated by a few taxa (~0.7% of diazotrophic phylotypes) which were mainly affiliated with Methylobacterium, Azospirillum, Bradyrhizobium, and Rhizobium. Furthermore, eight dominant taxa belonging to Azospirillum and Methylobacterium were identified as keystone diazotrophic taxa for three crops and were potentially associated with microbial network stability and crop yields. Metagenomic binning recovered 58 metagenome-assembled genomes (MAGs) from the phylloplane, and the majority of them were identified as novel species (37 MAGs) and harbored genes potentially related to multiple N metabolism processes (e.g., nitrate reduction). Notably, for the first time, a high-quality MAG harboring genes involved in the complete denitrification process was recovered in the phylloplane and showed high identity to Pseudomonas mendocina. Overall, these findings significantly expand our understanding of ecological drivers of crop diazotrophs and provide new insights into the potential microbial N metabolism in the phyllosphere.IMPORTANCEPlants harbor diverse nitrogen-fixing microorganisms (i.e., diazotrophic communities) in both belowground and aboveground tissues, which play a vital role in plant nitrogen supply and growth promotion. Understanding the assembly and temporal dynamics of crop diazotrophic communities is a prerequisite for harnessing them to promote plant growth. In this study, we show that the site-specific microbial species pool largely shapes the structure of diazotrophic communities in the leaves and roots of three cereal crops. We further identify keystone diazotrophic taxa in crop microbiomes and characterize potential microbial N metabolism pathways in the phyllosphere, which provides essential information for developing microbiome-based tools in future sustainable agricultural production.

AOB Nitrosospira cluster 3a.2 (D11) dominates N2O emissions in fertilised agricultural soils.

Ammonia-oxidation process directly contribute to soil nitrous oxide (N2O) emissions in agricultural soils. However, taxonomy of the key nitrifiers (within ammonia oxidising bacteria (AOB), archaea (AOA) and complete ammonia oxidisers (comammox Nitrospira)) responsible for substantial N2O emissions in agricultural soils is unknown, as is their regulation by soil biotic and abiotic factors. In this study, cumulative N2O emissions, nitrification rates, abundance and community structure of nitrifiers were investigated in 16 agricultural soils from major crop production regions of China using microcosm experiments with amended nitrogen (N) supplemented or not with a nitrification inhibitor (nitrapyrin). Key nitrifier groups involved in N2O emissions were identified by comparative analyses of the different treatments, combining sequencing and random forest analyses. Soil cumulative N2O emissions significantly increased with soil pH in all agricultural soils. However, they decreased with soil organic carbon (SOC) in alkaline soils. Nitrapyrin significantly inhibited soil cumulative N2O emissions and AOB growth, with a significant inhibition of the AOB Nitrosospira cluster 3a.2 (D11) abundance. One Nitrosospira multiformis-like OTU phylotype (OTU34), which was classified within the AOB Nitrosospira cluster 3a.2 (D11), had the greatest importance on cumulative N2O emissions and its growth significantly depended on soil pH and SOC contents, with higher growth at high pH and low SOC conditions. Collectively, our results demonstrate that alkaline soils with low SOC contents have high N2O emissions, which were mainly driven by AOB Nitrosospira cluster 3a.2 (D11). Nitrapyrin can efficiently reduce nitrification-related N2O emissions by inhibiting the activity of AOB Nitrosospira cluster 3a.2 (D11). This study advances our understanding of key nitrifiers responsible for high N2O emissions in agricultural soils and their controlling factors, and provides vital knowledge for N2O emission mitigation in agricultural ecosystems.

Streptomyces-triggered coordination between rhizosphere microbiomes and plant transcriptome enables watermelon Fusarium wilt resistance.

The use of microbial inoculant is a promising strategy to improve plant health, but their efficiency often faces challenges due to difficulties in successful microbial colonization in soil environments. To this end, the application of biostimulation products derived from microbes is expected to resolve these barriers via direct interactions with plants or soil pathogens. However, their effectiveness and mechanisms for promoting plant growth and disease resistance remain elusive. In this study, we showed that root irrigation with the extracts of Streptomyces ahygroscopicus strain 769 (S769) solid fermentation products significantly reduced watermelon Fusarium wilt disease incidence by 30% and increased the plant biomass by 150% at a fruiting stage in a continuous cropping field. S769 treatment led to substantial changes in both bacterial and fungal community compositions, and induced a highly interconnected microbial association network in the rhizosphere. The root transcriptome analysis further suggested that S769 treatment significantly improved the expression of the MAPK signalling pathway, plant hormone signal transduction and plant-pathogen interactions, particular those genes related to PR-1 and ethylene, as well as genes associated with auxin production and reception. Together, our study provides mechanistic and empirical evidences for the biostimulation products benefiting plant health through coordinating plant and rhizosphere microbiome interaction.

A recyclable Eu3+-functionalized dual-emissive metal-organic framework for portable, rapid detection and efficient removal of malachite green.

A europium-functionalized, dual-emissive, metal-organic framework-based fluorescence sensor (EuUCNDA) was constructed via post-synthetic modification of an UiO-66-type precursor through coordination interactions. EuUCNDA exhibited extremely high selectivity and sensitivity for malachite green (MG) with a low detection limit of 13.01 nM, a wide linear concentration range (0.05-50 µM), excellent anti-interference properties, a rapid response (<1 min), and the possibility of recycling. The good sensing performance of EuUCNDA enables the practical detection of MG in fish pond water and grass carp with good recoveries. Moreover, EuUCNDA can be reused for sensing MG and over 90% of fluorescence intensity can be restored after 7 cycles. Furthermore, EuUCNDA-embedded paper-based sensors combined with smartphone imaging afford portable and visual monitoring of MG in real samples. Notably, besides good sensing performance, EuUCNDA could efficiently remove MG from water. Hence, this work provides a recyclable and sensitive fluorescence sensor for portable, visual, rapid detection and efficient removal of MG.

[Effects and mechanisms of total flavones of Abelmoschus manihot in attenuating diabetic tubulopathy by targeting endoplasmic reticulum stress-induced cell apoptosis].

Renal tubular injury in patients with diabetic kidney disease(DKD) may be accompanied by glomerular and microvascular diseases. It plays a critical role in the progression of renal damage in DKD, and is now known as diabetic tubulopathy(DT). To explore the multi-targeted therapeutic effects and pharmacological mechanisms in vivo of total flavones of Abelmoschus manihot(TFA), an extract from traditional Chinese medicine for treating kidney disease, in attenuating DT, the authors randomly divided all rats into four groups: a normal control group(normal group), a DT model group(model group), a DT model+TFA-treated group(TFA group) and a DT model+rosiglitazone(ROS)-treated group(ROS group). The DT rat model was established based on the DKD rat model by means of integrated measures. After successful modeling, the rats in the four groups were continuously given double-distilled water, TFA suspension, and ROS suspension, respectively by gavage every day. After 6 weeks of treatment, all rats were sacrificed, and the samples of their urine, blood, and kidneys were collected. The effects of TFA and ROS on various indicators related to urine and blood biochemistry, renal tubular injury, renal tubular epithelial cell apoptosis and endoplasmic reticulum stress(ERS), as well as the activation of the protein kinase R-like endoplasmic reticulum kinase(PERK)-eukaryotic translation initiation factor 2α(eIF2α)-activating transcription factor 4(ATF4)-C/EBP homologous protein(CHOP) signaling pathway in the kidney of the DT model rats were investigated. The results indicated that hypertrophy of renal tubular epithelial cells, renal tubular hyperplasia and occlusion, as well as interstitial extracellular matrix and collagen deposition occurred in the DT model rats. Moreover, significant changes were found in the expression degree and the protein expression level of renal tubular injury markers. In addition, there was an abnormal increase in tubular urine proteins. After TFA or ROS treatment, urine protein, the characteristics of renal tubular injury, renal tubular epithelial cell apoptosis and ERS, as well as the activation of the PERK-eIF2α-ATF4-CHOP signaling pathway in the kidney of the DT model rats were improved to varying degrees. Therein, TFA was superior to ROS in affecting the pathological changes in renal tubule/interstitium. In short, with the DT model rats, this study demonstrated that TFA could attenuate DT by multiple targets through inhibiting renal tubular ERS-induced cell apoptosis in vivo, and its effect and mechanism were related to suppressing the activation of the PERK-eIF2α-ATF4-CHOP signaling pathway in the kidney. These findings provided preliminary pharmacological evidence for the application of TFA in the clinical treatment of DT.

[Effect and mechanism of Dahuang Zhechong Pills in improving liver aging in rats by regulating ROS-mediated PI3K/Akt/FoxO4 signaling pathway].

Recent studies have shown that the occurrence and development of common liver diseases, including non-alcoholic fatty liver disease, cirrhosis, and liver cancer, are related to liver aging(LA). Therefore, to explore the effect and mechanism of Dahuang Zhechong Pills(DHZCP), a traditional classic prescription in improving LA with multiple targets, the present study randomly divided 24 rats into a normal group, a model group, a DHZCP group, and a vitamin E(VE) group, with six rats in each group. The LA model was induced by continuous intraperitoneal injection of D-galactose(D-gal) in rats. For the LA model rats, the general situation was evaluated by aging phenotype and body weight(BW). LA was assessed by the pathological characteristics of hepatocyte senescence, hepatic function indexes, the staining characteristics of phosphorylated histone family 2A variant(γ-H2AX), and the expression levels of cell cycle arrest proteins(P21, P53, P16) and senescence-associated secretory phenotype(SASP) in the liver. The activation of the reactive oxygen species(ROS)-mediated phosphatidylinositol-3 kinase(PI3K)/protein kinase B(Akt)/forkhead box protein O4(FoxO4) signaling pathway was estimated by hepatic ROS expression feature and the protein expression levels of the key signaling molecules in the PI3K/Akt/FoxO4 signaling pathway. The results showed that after the treatment with DHZCP or VE for 12 weeks, for the DHZCP and VE groups, the characterized aging phenotype, BW, pathological characteristics of hepatocyte senescence, hepatic function indexes, relative expression of ROS in the liver, protein expression levels of key signaling molecules including p-PI3K, p-Akt, and FoxO4 in the liver, staining characteristics of γ-H2AX, and the protein expression levels of P16, P21, P53, interleukin-6(IL-6), and tumor necrosis factor-α(TNF-α) in the liver were improved, and the effects of DHZCP and VE were similar. Based on the D-gal-induced LA model in rats, this study demonstrates that DHZCP can ameliorate LA with multiple targets in vivo, and its effects and mechanism are related to regulating the activation of the ROS-mediated PI3K/Akt/FoxO4 signaling pathway in the liver. These findings are expected to provide new pharmacological evidence for the treatment of DHZCP in aging-related liver diseases.

Detachable Porous Organic Polymers Responsive to Light and Heat.

Stimuli-responsive porous materials have captured much attention due to the on-demand tunable properties. Most reported stimuli-responsive porous materials are based on molecule isomerism or host-guest interaction, and it is highly desired to develop new types based on different responsive mechanism. Herein, inspired by natural cells which have the ability to fuse and divide induced by external stimulation, we report a new type of stimuli-responsive porous material based on detachment mechanism. A detachable porous organic polymer, namely DT-POP-1, is fabricated from the polymerization of anthracene-containing monomer (AnMon) when irradiated by 365 nm UV light. DT-POP-1 can detach into the monomer AnMon when irradiated with 275 nm UV light or heat. Such polymerization/detachment is reversible. The detachment results in a big difference in porosity and adsorption capacity, making the present detachable porous polymer highly promising in adsorptive separation and drug delivery.

[Horizontal Variation Characteristics of Alpine Grassland Soil Function and Vertical Changes Along Soil Genetic Horizons in the Three-River Headwaters Region].

The Three-River Headwaters region is a hotspot for studying the response of soil function to climate change. To study the horizontal variation characteristics of alpine grassland soil function and vertical changes along soil genetic horizons, soil functional indicators (including respiration, nitrogen conversion rate, and enzymatic activity) of different genetic horizons in alpine grassland soil profiles and their correlations with environmental factors were analyzed. The results showed that there were no significant differences in soil functional characteristics between alpine meadows and steppes, and topsoil had higher respiration rates, nitrogen conversion rates, and enzymatic activities than those of subsoil. Total nitrogen was a key driver of soil functional characteristics in different genetic horizons, explaining 18.3%, 21.4%, and 27.5% of the horizontal variation in functional characteristics, respectively. Climate and vegetation factors mainly affected soil function indirectly by changing soil physicochemical properties in topsoil, but atmospheric nitrogen deposition still affected soil function in subsoil. These results indicate the significant nitrogen limitation of alpine grassland soil in the Three-River Headwaters region, and the findings provide a new insight into the maintenance of soil functional diversity and the response to climate change in the context of global climate change.

[Coupling Relationship Between Soil Functions and Environmental Factors Along an Altitudinal Gradient: A Case Study of the Meili Mountain].

Soil respiration and extracellular enzyme activity are important components of the material cycle of mountain ecosystems and play key roles in maintaining ecosystem functions. To explore the coupling relationship between soil functions and environmental factors, the soil functional indicators, environmental factors, and effects of altitude on the soil function of 36 soil samples from 12 altitudes of the Meili Mountain were analyzed. The results showed that there were significant differences in soil respirations and enzyme activities among altitudes of Meili Mountain, and high-altitude areas had higher soil functions. Soil functions increased with altitudinal difference. PCA analysis showed that the first three axes explained 56.7%, 17.4%, and 8.7% of the variance in soil functional elevation change, respectively, indicating that the functional changes related to carbon and phosphorus were higher than those related to nitrogen. There were significant correlations between environmental factors and soil functional indicators; soil function indicators had stronger correlations with soil physicochemical properties than with climatic factors. Altitude mainly affected soil function indirectly by affecting soil physicochemical properties and climatic factors. These results have great scientific significance for improving the understanding of the material cycle and ecological function of the Meili Mountain ecosystem and provide an important reference for in-depth study of the altitude distribution pattern and evolution characteristics of the soil function of the mountain ecosystem.

Effect of a bioactive glass-based root canal sealer on root fracture resistance ability.

Background/purpose: The root fracture resistance of endodontically treated teeth is decreased significantly, and it is more likely to fracture. This study aimed to evaluate the effect of a novel root canal sealer based on bioactive glass (BG) on root fracture resistance and explore its mechanism. Materials and methods: The BG-based root canal sealer (BG Sealer) was prepared by mixing a kind of bioactive glass (10.8% P2O5, 54.2% SiO2, 35% CaO, mol.%, named PSC), zirconia (ZrO2) powder, sodium alginate (SA) and phosphate solution (PS). A pH meter was used to measure the pH of simulated body fluid (SBF) after immersion with BG Sealer at different time. After preparing the samples of BG sealer with a diameter of 4 mm and a height of 6 mm, the compressive strength was tested by a universal testing machine. The scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) were used to detect and analyze the mineral status of root canal systems filled with BG Sealer. The push out test was used to measure the push out bond strength of BG Sealer. The fracture resistance of root canals filled with BG Sealer was detected by the compressive loading test. Bioceramic root canal sealer iRoot SP was set as the control group. Results: (1) Physicochemical properties: The pH value of SBF immersed with BG Sealer increased slightly up to 7.68, while the pH of SBF immersed with iRoot SP increased to 12.08. The compressive strength of the novel BG Sealer was 4.62 ± 1.70 MPa, which was lower than that of iRoot SP (P < 0.05). (2) Mineralization: The hydroxyapatite layers were observed on the surface of BG Sealer and iRoot SP after being immersed in SBF for 4 weeks. BG Sealer and iRoot SP were both able to penetrate into the dentin tubules, duplicate the morphology of root canals well, and form a layer of hydroxyapatite. (3) Adhesion to dentin: There was no significant difference between the push out bond strength of the novel BG Sealer and iRoot SP (P > 0.05). (4) Fracture resistance: After immersion in SBF for 4 weeks, the fracture resistance of roots filled with BG Sealer and iRoot SP was 454.16 ± 155.39 N and 445.50 ± 164.73 N, respectively, both of which were not statistically different from that of the roots unprepared and unfilled (394.07 ± 62.12 N) (P > 0.05), whereas higher than that of the roots prepared and unfilled (235.36 ± 83.80 N) (P < 0.05). Conclusion: The novel BG Sealer has good adhesion to the root dentin, can penetrate into the dentin tubules to generate minerals, and meanwhile can improve the fracture resistance of the roots after root canal treatment. It is expected to be a bioactive root canal sealer with good clinical application prospects.

A highly water-stable dual-emission fluorescent probe based on Eu3+-loaded MOF for the simultaneous detection and quantification of Fe3+ and Al3+ in swine wastewater.

A novel dual-emissive Eu3+-loaded metal-organic framework (MOF) is designed and successfully fabricated by introducing 2-hydroxyterephthalic acid (H2BDC-OH) and Eu3+ ions into an UiO-66-type MOF material. The obtained MOF, here referred to as EuUCH, exhibits dual emission at 450 and 614 nm, and both emissions are quite stable in aqueous media in the pH range of 4-11. EuUCH is characterized by a high selectivity and sensitivity toward Fe3+ and Al3+, which yield different responsive modes. The two emissions of EuUCH are quenched by Fe3+; by contrast, only the emission at 450 nm is quenched by Al3+ showing a ratiometric fluorescence signal. More importantly, as there is no clear interference between the signals of Fe3+ and Al3+, EuUCH is successfully utilized for the simultaneous detection of Fe3+ and Al3+ in their mixtures. In addition, the simultaneous quantification of Fe3+ and Al3+ is achieved in more complicated swine wastewater with good recoveries. This work provides a water-stable dual-emissive probe and the possibility to achieve the simultaneous quantification of Fe3+ and Al3+ in complicated environment wastewater.

Morpho-Molecular Characterization of Microfungi Associated with Phyllostachys (Poaceae) in Sichuan, China.

In the present study, we surveyed the ascomycetes from bamboo of Phyllostachys across Sichuan Province, China. A biphasic approach based on morphological characteristics and multigene phylogeny confirmed seven species, including one new genus, two new species, and five new host record species. A novel genus Paralloneottiosporina is introduced to accommodate Pa. sichuanensis that was collected from leaves of Phyllostachys violascens. Moreover, the newly introduced species Bifusisporella sichuanensis was isolated from leaves of P. edulis, and five species were newly recorded on bamboos, four species belonging to Apiospora, viz. Ap. yunnana, Ap. neosubglobosa, Ap. jiangxiensis, and Ap. hydei, and the last species, Seriascoma yunnanense, isolated from dead culms of P. heterocycla. Morphologically similar and phylogenetically related taxa were compared. Comprehensive descriptions, color photo plates of micromorphology are provided.

A dual-channel "on-off-on" fluorescent probe for the detection and discrimination of Fe3+ and Hg2+ in piggery feed and swine wastewater.

Blue-fluorescent blood-CDs were synthesized through a one-pot hydrothermal method using a mixture of chicken blood and trisodium citrate and then explored as a fluorescent probe for detecting Fe3+ and Hg2+. The probe showed excellent selectivity and sensitivity towards Fe3+ and Hg2+ with a dramatic "on-off" fluorescence response. F- recovered the fluorescence quenching by Fe3+, and Al3+ recovered the fluorescence quenching by Hg2+, showing an "off-on" fluorescence response. The blood-CDs were used as an "on-off-on" dual-channel fluorescent sensor for the detection and discrimination of Fe3+ and Hg2+ ions. The probe showed wide linear ranges for determination of Fe3+ (0-100 µM) and Hg2+ (0-120 µM) with low detection limits of 0.23 µM for Fe3+ and 0.17 µM for Hg2+. This probe was practically applied for the determination of Fe3+ and Hg2+ in piggery feed and wastewater with good recoveries. This work provides a fluorescent probe for the quantification of Fe3+ and Hg2+ in livestock feed and environmental water samples.

Distribution Characteristics of Soil Viruses Under Different Precipitation Gradients on the Qinghai-Tibet Plateau.

Viruses are extremely abundant in the soil environment and have potential roles in impacting on microbial population, evolution, and nutrient biogeochemical cycles. However, how environment and climate changes affect soil viruses is still poorly understood. Here, a metagenomic approach was used to investigate the distribution, diversity, and potential biogeochemical impacts of DNA viruses in 12 grassland soils under three precipitation gradients on the Qinghai-Tibet Plateau, which is one of the most sensitive areas to climate change. A total of 557 viral operational taxonomic units were obtained, spanning 152 viral families from the 30 metagenomes. Both virus-like particles (VLPs) and microbial abundance increased with average annual precipitation. A significant positive correlation of VLP counts was observed with soil water content, total carbon, total nitrogen, soil organic matter, and total phosphorus. Among these biological and abiotic factors, SWC mainly contributed to the variability in VLP abundance. The order Caudovirales (70.1% of the identified viral order) was the predominant viral type in soils from the Qinghai-Tibet Plateau, with the Siphoviridae family being the most abundant. Remarkably, abundant auxiliary carbohydrate-active enzyme (CAZyme) genes represented by glycoside hydrolases were identified, indicating that soil viruses may play a potential role in the carbon cycle on the Qinghai-Tibet Plateau. There were more diverse hosts and abundant CAZyme genes in soil with moderate precipitation. Our study provides a strong evidence that changes in precipitation impact not only viral abundance and virus-host interactions in soil but also the viral functional potential, especially carbon cycling.

A luminescent Eu3+-functionalized MOF for sensitive and rapid detection of tetracycline antibiotics in swine wastewater and pig kidney.

Tetracyclines (TCs), a type of antibiotics, are widely used in human therapy and animal husbandry. Public concerns about tetracyclines residues have been raised due to their negative impact on the environment and food, causing bacterias drug resistance and human health concerns. In this work, a luminescent europium MOF (EuUCBA) is constructed via post-synthetic attachment of Eu3+ into a UiO-66 type MOF. The luminescent of EuUCBA exhibits high stability in aqueous media in the pH range of 4-11. Among 36 common veterinary drugs, the synthesized probe is highly selective and sensitive to six tetracyclines with low detection limits of 0.118 µM, 0.228 µM, 0.102 µM, 0.138 µM, 0.206 µM, and 0.078 µM for oxytetracycline (OTC), chlortetracycline (CTC), methylenetetracycline (MTC), minocycline (MOC), tetracycline (TC), and doxycycline (DOXY), respectively. Furthermore, the probe shows good anti-interference ability and fast response. Finally, EuUCBA was successfully to detect DOXY in swine wastewater and pig kidney with good recoveries. This work provides an excellent fluorescent sensor for highly selective and rapid detection of TCs residues in wastewater and complex biological samples.

A novel bioactive glass-based root canal sealer in endodontics.

BACKGROUND/PURPOSE: Bioactive glass (BG), one type of bioceramics, shows similar or better characteristics to calcium silicate which has been regarded as a promising root filling material in endodontics. This study aimed to develop a novel BG-based root canal sealer for endodontics. MATERIALS AND METHODS: The novel BG-based root canal sealer was composed of phytic acid derived bioactive calcium phosphosilicate glass named PSC mixed with zirconium oxide (ZrO2) as powder, and phosphate solution (PS) dissolved with sodium alginate (SA) named PS-SA as liquid. Moreover, the physicochemical properties, mineralization, sealing ability and biocompatibility of the novel BG-based root canal sealer were evaluated. RESULTS: This study developed a novel BG-based sealer named BGS-SA-Zr which contained the powder of PSC and ZrO2 and the liquid of PS-SA. Results indicated that the flow, film thickness and radiopacity of BGS-SA-Zr conformed to ISO 6876:2012. The setting time and solubility of BGS-SA-Zr were 53.7 ±â€¯1.5 min and 21.46 ±â€¯0.54%, respectively. The pH value of the simulated body fluid (SBF) immersed with BGS-SA-Zr raised slightly up to 7.70. The CCK-8 assay indicated that BGS-SA-Zr had no cytotoxic effects on MG-63 cells. After immersion in SBF for 4 weeks, dense hydroxyapatite crystals were observed on the surface of BGS-SA-Zr. Furthermore, there was no difference in the sealing ability between BGS-SA-Zr and the bioceramic sealer iRoot SP whether setting at 1 day or immersed in SBF for 4 weeks (P > 0.05). CONCLUSION: Our results suggest that the novel BG-based sealer may be a promising sealer for endodontic treatment.

Characterisation of novel Tn7-derivatives and Tn7-like transposon found in Proteus mirabilis of food-producing animal origin in China.

OBJECTIVES: This study aimed to clarify the characteristics of Tn7-derivatives transposons in MDR Proteus mirabilis strains isolated from anal swabs of chicken and swine in China from 2015-2020. METHODS: The Tn7 tnsA gene was screened in 207 P. mirabilis isolates by polymerase chain reaction (PCR). These strains were subjected to antimicrobial susceptibility testing. Illumina Hiseq (200 × coverage) was used for genome sequencing. Transposon maps were completed by PCR and Sanger sequencing and analysed by BLAST. RESULTS: The Tn7 tnsA gene was detected in 21 strains by PCR. Eight novel Tn7-derivatives, named Tn6667, Tn6668, Tn6669, Tn6670, Tn7095, Tn7096, Tn7097 and Tn7098, were characterised. Three types of hybrid class 2/1 integrons were found at the right end of Tn7 derivatives. A novel Tn7-like transposon Tn6666 with an active integrase gene intI2, whose transposition module shows 93% nucleotide identity to the corresponding region of Tn7, was characterised in three strains. Tn6666 is also found next to Tn7097 or Tn7098 in the chromosomes of two clonally related P. mirabilis strains. The number of resistance genes carried by the novel transposons varied from 1 to 18. A novel variant of class A extended-spectrum beta-lactamase gene, blaPER-16, with eight base substitutions compared with blaPER-12, was harboured by Tn7098. CONCLUSION: Our study characterised diverse novel Tn7-derivatives and a new Tn7-like transposon in P. mirabilis. An active integrase gene intI2 might promote the diversification of Tn7-like transposons. More attention should be paid to the prevalence and evolution of Tn7-derivatives and Tn7-like transposons and antimicrobial resistance genes they carry.

COVID-19 risk perception and tourist satisfaction: A mixed-method study of the roles of destination image and self-protection behavior.

This study aimed to examine the effects of COVID-19 risk perception on negative destination image and self-protection behavior, and the resultant effects on tourist satisfaction. Hence, this study applied a continuous interpretive mixed-method design combining quantitative and qualitative analyses. A quantitative survey (n = 486) in the cities of Ningbo, Huangshan, and Chengdu, China, and 19 qualitative interviews were conducted online. The results of the quantitative study show that: (1) Risk perception and negative destination image are antecedent variables influencing tourist satisfaction, and (2) there are significant positive correlations between risk perception and negative destination image, risk perception and tourist self-protection behavior, and negative destination image and tourist self-protection behavior. Moreover, (3) negative destination image had a partial mediating effect between risk perception and satisfaction. Furthermore, to supplement the research data and expand the quantitative findings, this study further examined whether the above variables are related to tourist satisfaction, through in-depth interviews with tourists. The findings showed that COVID-19 risk perception, negative destination image, and self-protection behavior all affect tourist satisfaction. The findings provide valuable crisis management suggestions for the government and should contribute to the efforts of tourist destinations to build a healthy and safe image, thereby contributing to the sustainable development of tourism industries in the post-epidemic era.

Clonal spread and horizontal transfer mediate dissemination of phenicol-oxazolidinone-tetracycline resistance gene poxtA in enterococci isolates from a swine farm in China.

The emergence of the phenicol-oxazolidinone-tetracycline resistance gene poxtA becomes a significant challenge for public health, since it confers a decreased susceptibility not only to the last resort drug linezolid, but also to florfenicol and doxycycline widely used in veterinary medicine. To determine the dissemination mechanism of poxtA in enterococci isolates from different healthy pigs in the swine farm, a total of 178 florfenicol-resistant enterococci isolates were collected from 400 fresh faecal swabs in a swine farm in China. The poxtA gene was detected in 11 (6.18 %) enterococci isolates, including 8 E. faecium, 2 E. hirae and 1 E. casseliflavus isolates. Whole genome sequencing indicated that the eight poxtA-harbouring E. faecium strains belonged to four different sequence types, including ST156 and three new STs, ST1818, ST1819 and ST1820. Five out of the 11 poxtA-positive enterococci isolates also harboured optrA gene. Moreover, E. casseliflavus strain DY31 co-harboured poxtA, optrA and cfr. Seven different poxtA-harbouring plasmids were obtained through Nanopore combined with Illumina sequencing. The poxtA-harbouring plasmids exhibited high genetic variation, six out of which belonged to rep2 plasmid of Inc18 family. The poxtA gene was flanked by IS1216E in the left and/or right ends.The optrA and cfr genes were located on different plasmids, respectively, but those genes could be co-transferred with poxtA gene into the recipient E. faecalis strain by electrotransformation. Our study highlights that both clonal spread and horizontal transfer mediated by Inc18 plasmid and IS1216E promote the dissemination of poxtA in enterococci isolates from different healthy pigs in the swine farm.