Development of High-Performance and Multifunctional Nanoparticles Powered the Integrated Diagnosis and Treatment of Escherichia coli O157:H7.

Pathogenic diseases that trigger food safety remain a noteworthy concern due to substantial public health, economic, and social burdens worldwide. It is vital for developing an integrated diagnosis and treatment strategy for bacteria, which could achieve quick detection of pathogenic bacteria and the inhibition of multidrug-resistant bacteria. Herein, we reported an organic molecule (M-3) possessed strong light capture capacity, emerging a low energy gap and ΔEST. Subsequently, M-3 was integrated into a nanostructured system (BTBNPs) with excellent ROS generation, light absorption capability, and photothermal performance. Reactive oxygen species (ROS) generated by BTBNPs were mainly free radicals from a type I mechanism, and the high photothermal conversion efficiency of BTBNPs was 41.26%. Benefiting from these advantages of BTBNPs, BTBNPs could achieve a ∼99% antibacterial effect for Escherichia coli O157:H7 with 20 µM dosage and 5 min of irradiation. Furthermore, the limit of detection (LoD) of the proposed BTBNPs-LFIA (colorimetric and photothermal modalities) for detecting E. coli O157:H7 was 4105 and 419 CFU mL-1, respectively. Overall, this work is expected to provide a new and sophisticated perspective for integrated diagnosis and treatment systems regarding pathogenic bacteria.

Efficient Photothermal Sensor Based on Coral-Like Hollow Gold Nanospheres for the Sensitive Detection of Sulfonamides.

Gold nanoparticles (AuNPs), universally regarded as colorimetric signal reporters, are widely employed in lateral flow immunoassays (LFIAs). However, it is difficult for AuNPs-LFIA to achieve a wide range and sensitive detection. Herein, novel coral-like hollow gold nanospheres (CHGNPs) are synthesized. The growth of gold nanospheres can be regulated to obtain a multibranched and hollow construction. The obtained CHGNPs possess intense broadband absorption across the visible to near-infrared region, exhibiting a high molar extinction coefficient of 14.65 × 1011 M-1 cm-1 and a photothermal conversion efficiency of 79.75%. Thus, the photothermal/colorimetric dual-readout LFIA is developed based on CHGNPs (CHGNPs-PT-LFIA and CHGNPs-CM-LFIA) to effectively improve the detection sensitivity and broaden the detection range in regard to sulfonamides (SAs). The limits of detection of the CHGNPs-PT-LFIA and CHGNPs-CM-LFIA reached 1.9 and 2.8 pg mL-1 for the quantitative detection of sulfaquinoxaline, respectively, which are 6.3-fold and 4.3-fold lower than that of the AuNPs-LFIA. Meanwhile, the CHGNPs-PT-LFIA broadened the detection range to three orders of magnitude, which ranged from 2.5 to 5000 pg mL-1 . The synthesized photothermal CHGNPs have been proven effective in improving the performance of the LFIA and provide a potential option for the construction of sensing platforms.

Phage based magnetic capture method as an aid for real time RPA detection of Salmonella spp. in milk.

Salmonella is a major cause of foodborne diseases worldwide. Conventional rapid assays for detecting Salmonella in real samples often encounter severe matrix interference or detect the limited number of species of a genus, resulting the inaccuracy of detection. In this study, we developed a method that combined phage-based magnetic capture with real time recombinase polymerase amplification (RPA) for the rapid, highly sensitive, and specific detection of Salmonella in milk with an ultra-low detection limit. The Felix O-1 phage-conjugated magnetic beads (O-1 pMBs) synthesized in this method showed excellent capture ability for Salmonella spp. and ideal specificity for non-Salmonella strains. After O-1 pMBs-based magnetic separation, the limit of detection (LOD) of the real time RPA assay was 50 cfu/mL in milk samples, which was significantly increased by a magnitude of 3-4 orders. The method exhibited a high sensitivity (compatibility) of 100% (14/14) for all tested Salmonella serotype strains and an ideal specificity (exclusivity) of 100% (7/7) for the tested non-Salmonella strains. The entire detection process including Salmonella capture, DNA extraction, and real time RPA detection was completed within 1.5 h. Furthermore, milk samples spiked with 10 cfu/25 mL of Salmonella were detected positive after cultured in buffered peptone water for only 3 h. Therefore, the proposed method could be an alternative for the rapid and accurate detection of Salmonella.

High-resolution melting real-time PCR assays for subtyping of five diarrheagenic Escherichia coli by a single well in milk.

Diarrheagenic Escherichia coli (DEC) is a kind of foodborne pathogen that poses a significant threat to both food safety and human health. To address the current challenges of high prevalence and difficult subtyping of DEC, this study developed a method that combined multiplex polymerase chain reaction (PCR) with high resolution melting (HRM) analysis for subtyping 5 kinds of DEC. The target genes are amplified by multiplex PCR in a single well, and HRM curve analysis was applied for distinct amplicons based on different melting temperature (Tm) values. The method enables discrimination of different DEC types based on characteristic peaks and distinct Tm values in the thermal melting curve. The assay exhibited 100% sensitivity and 100% specificity with a detection limit of 0.5-1 ng/µL. The results showed that different DNA concentrations did not influence the subtyping results, demonstrating this method owed high reliability and stability. In addition, the method was also used for the detection and subtyping of DEC in milk. This method streamlines operational procedures, shorts the detection time, and offers a novel tool for subtyping DEC.

Epidemiological and Whole Genome Sequencing Analysis of Restaurant Salmonella Enteritidis Outbreak Associated with an Infected Food Handler in Jiangxi Province, China, 2023.

In China, Salmonella is one of the most frequent causes of bacterial gastroenteritis, and food handlers in restaurants as an important contaminated source were rarely reported. In May 2023, an outbreak of Salmonella enterica serovar Enteritidis infection in a restaurant in Jiangxi Province, China, was investigated. Cases were interviewed. Stool samples from cases, anal swabs from restaurant employees, suspicious raw food materials, and semifinished food were collected and examined. Pulsed-field gel electrophoresis (PFGE) and whole genome sequencing (WGS) were performed to determine the relatedness of the pathogen isolates. Antimicrobial resistance genes and virulence genes of isolates were analyzed by WGS. The antimicrobial profile of the isolates was detected by broth microdilution, which involved 20 different antibiotics. Among the 31 patrons, 26 showed gastrointestinal symptoms. Five Salmonella Enteritidis strains were isolated from patients (2), semifinished food (2), and food handler (1). The results of PFGE and single-nucleotide polymorphism showed that these five isolates were identical clones. These findings demonstrated that this outbreak was a restaurant Salmonella Enteritidis outbreak associated with an infected food handler. The rates of resistance to nalidixic acid and colistin and intermediate resistance to ciprofloxacin were 100%, 80%, and 100%, respectively. These outbreak isolates harbored point mutation gyrA p.D87G. The cause of inconsistency between the genotype and phenotype of resistance was deeply discussed. A total of 107 virulence genes were found in each isolate, with many being associated with Salmonella pathogenicity island (SPI)-1 and SPI-2. As an overlooked contamination source, infected food handlers can easily cause large-scale outbreaks. This outbreak highlighted that the government should enhance the training and supervision of food hygiene and safety for food handlers to prevent foodborne outbreaks.

Sensitive fluorescence ELISA with streptavidin scaffolded DNA tetrads for the detection of Escherichia coli O157:H7.

Escherichia coli O157:H7 poses a threat to humans. Traditional ELISA is not a sensitive method for the detection of E. coli O157:H7. Here, an efficient method was designed for improving the load capacity of alkaline phosphatase (ALP) with streptavidin scaffolded DNA tetrad (SS-DNAt). With more ALP, more ascorbic acid 2-phosphate was catalyzed to ascorbic acid that was used to synthesize fluorescence poly adenine-thymine-templated copper nanoclusters. Based on SS-DNAt, fluorescence ELISA was successfully proposed for improving the sensitivity for detection of E. coli O157:H7 in milk samples. The method showed a linear range of 104 to 106 cfu/mL. The limit of detection of fluorescence ELISA was 3.75 × 103 cfu/mL and 6.16-fold better than that of traditional ELISA. The recovery of the fluorescence ELISA was 86.7 to 93.6% with the coefficient of variation of 5.6 to 10.5% in milk. This method could be used to detect hazardous material in food.

A Novel Technique for Reduction and Fixation of Severe Extracapsular Condylar Fracture.

Introducing a novel surgical technique that uses 2 screws and 3 titanium plates to reduce and fix an extracapsular condylar fracture. This technique has been used on 18 sides of extracapsular condylar fracture over the last 3 years in the Department of Oral and Cranio-Maxillofacial Science of Shanghai Ninth People's Hospital without severe complications in clinical practice. Applying this technique, the dislocated condylar segment can be reduced accurately and fixed efficiently.

I2/I--mediated fluorescence quenching of an Ag+-doped gold nanocluster-based immunoassay for sensitive detection of Escherichia coli O157:H7 in milk.

Escherichia coli O157:H7 is a type of hazardous bacteria in the field of food safety. A sensitive and effective method is urgently needed to detect it, avoiding enormous harm for the human health. In this study, we synthesized stable Ag+-doped gold nanoclusters (Ag-AuNC) with a fluorescence intensity 4.8 times stronger than that of AuNC. It was further demonstrated that Ag0 existing in the AuNC core and a fraction of Ag+ anchored on the AuNC shell eliminated the surface defects and improved the luminescent properties of AuNC. A combination of I2 and I- was used to quench fluorescence-enhanced Ag-AuNC, which was first applied in ELISA for detecting E. coli O157:H7 to improve the sensitivity. In the presence of E. coli O157:H7, the biotinylated anti-E. coli O157:H7 mAb and streptavidin-alkaline phosphatase would be immobilized and catalyze l-ascorbic acid 2-phosphate sesquimagnesium salt hydrate to produce ascorbic acid. After addition of KIO3, I2/I- were generated. The I2 could trigger oxidative etching of Ag-AuNC and I- could combine with Ag+ to decrease the Ag+ concentration of Ag-AuNC, which resulted in fluorescence quenching of Ag-AuNC. Under optimal conditions, the linear range of I2/I--mediated fluorescence quenching of Ag-AuNC-based immunoassay for detecting E. coli O157:H7 was 3.3 × 103 to 106 cfu/mL, with a detection limit of 9.2 × 102 cfu/mL, 10.7-fold lower than that of the traditional ELISA. The proposed immunoassay exhibits excellent sensitivity, specificity, recovery, and accuracy, which is useful for quantitative detection of E. coli O157:H7 in food safety.

Overexpression of a Senescence-Related Gene CpSRG1 from Wintersweet (Chimonanthus praecox) Promoted Growth and Flowering, and Delayed Senescence in Transgenic Arabidopsis.

Plant senescence is a complex process that is controlled by developmental regulation and genetic programs. A senescence-related gene CpSRG1, which belongs to the 2OG-Fe(II) dioxygenase superfamily, was characterized from wintersweet, and the phylogenetic relationship of CpSRG1 with homologs from other species was investigated. The expression analysis by qRT-PCR (quantitative real-time PCR) indicated that CpSRG1 is abundant in flower organs, especially in petals and stamens, and the highest expression of CpSRG1 was detected in stage 6 (withering period). The expression patterns of the CpSRG1 gene were further confirmed in CpSRG1pro::GUS (ß-glucuronidase) plants, and the activity of the CpSRG1 promoter was enhanced by exogenous Eth (ethylene), SA (salicylic acid), and GA3 (gibberellin). Heterologous overexpression of CpSRG1 in Arabidopsis promoted growth and flowering, and delayed senescence. Moreover, the survival rates were significantly higher and the root lengths were significantly longer in the transgenic lines than in the wild-type plants, both under low nitrogen stress and GA3 treatment. This indicated that the CpSRG1 gene may promote the synthesis of assimilates in plants through the GA pathway, thereby improving growth and flowering, and delaying senescence in transgenic Arabidopsis. Our study has laid a satisfactory foundation for further analysis of senescence-related genes in wintersweet and wood plants. It also enriched our knowledge of the 2OG-Fe(II) dioxygenase superfamily, which plays a variety of important roles in plants.

Full-Length Transcriptome Characterization and Functional Analysis of Pathogenesis-Related Proteins in Lilium Oriental Hybrid 'Sorbonne' Infected with Botrytis elliptica.

Gray mold (Botrytis elliptica) causes a deleterious fungal disease that decreases the ornamental value and yield of lilies. Lilium oriental hybrid 'Sorbonne' is a variety that is resistant to gray mold. Understanding the mechanism of resistance against B. elliptica infection in 'Sorbonne' can provide a basis for the genetic improvement in lily plants. In this study, a PacBio Sequel II system was used to sequence the full-length transcriptome of Lilium 'Sorbonne' after inoculation with B. elliptica. A total of 46.64 Gb subreads and 19,102 isoforms with an average length of 1598 bp were obtained. A prediction analysis revealed 263 lncRNAs, and 805 transcription factors, 4478 simple sequence repeats, and 17,752 coding sequences were identified. Pathogenesis-related proteins (PR), which may play important roles in resistance against B. elliptica infection, were identified based on the full-length transcriptome data and previously obtained second-generation transcriptome data. Nine non-redundant potential LhSorPR proteins were identified and assigned to two groups that were composed of two LhSorPR4 and seven LhSorPR10 proteins based on their genetic relatedness. The real-time quantitative reverse transcription PCR (qRT-PCR) results showed that the patterns of expression of nine differentially expressed PR genes under B. elliptica stress were basically consistent with the results of transcriptome sequencing. The pattern of expression of LhSorPR4s and LhSorPR10s genes in different tissues was analyzed, and the expression of each gene varied. Furthermore, we verified the function of LhSorPR4-2 gene in Lilium. The expression of LhSorPR4-2 was induced by phytohormones such as methyl jasmonate, salicylic acid, and ethephon. Moreover, the promoter region of LhSorPR4-2 was characterized by several functional domains associated with phytohormones and stress response. The overexpression of LhSorPR4-2 gene in 'Sorbonne' increased the resistance of the lily plant to B. elliptica and correlated with high chitinase activity. This study provides a full-length transcript database and functionally analyzed the resistance of PR gene to B. elliptica in Lilium, thereby introducing the candidate gene LhSorPR4-2 to breed resistance in Lilium.

Functional Characterization of the CpNAC1 Promoter and Gene from Chimonanthus praecox in Arabidopsis.

The NAC (NAM, ATAF, and CUC) gene family is one of the largest plant-specific transcription factor families. Its members have various biological functions that play important roles in regulating plant growth and development and in responding to biotic and abiotic stresses. However, their functions in woody plants are not fully understood. In this study, we isolated an NAC family member, the CpNAC1 promoter and gene, from wintersweet. CpNAC1 was localized to the nucleus and showed transcriptional activation activity. qRT-PCR analyses revealed that the gene was expressed in almost all tissues tested, with the highest levels found in mature leaves and flower buds. Moreover, its expression was induced by various abiotic stresses and ABA treatment. Its expression patterns were further confirmed in CpNAC1pro:GUS (ß-glucuronidase) plants. Among all the transgenic lines, CpNAC1pro-D2 showed high GUS histochemical staining and activity in different tissues of Arabidopsis. Furthermore, its GUS activity significantly increased in response to various abiotic stresses and ABA treatment. This may be related to the stress-related cis-elements, such as ABRE and MYB, which clustered in the CpNAC1pro-D2 segment, suggesting that CpNAC1pro-D2 is the core segment that responds to abiotic stresses and ABA. In addition, CpNAC1-overexpressed Arabidopsis plants had weaker osmosis tolerance than the wild-type plants, demonstrating that CpNAC1 may negatively regulate the drought stress response in transgenic Arabidopsis. Our results provide a foundation for further analyses of NAC family genes in wintersweet, and they broaden our knowledge of the roles that NAC family genes may play in woody plants.

CpMAX1a, a Cytochrome P450 Monooxygenase Gene of Chimonanthus praecox Regulates Shoot Branching in Arabidopsis.

Strigolactones (SLs) are a class of important hormones in the regulation of plant branching. In the model plant Arabidopsis, AtMAX1 encodes a cytochrome P450 protein and is a crucial gene in the strigolactone synthesis pathway. Yet, the regulatory mechanism of MAX1 in the shoot branching of wintersweet (Chimonanthus praecox) remains unclear. Here we identified and isolated three MAX1 homologous genes, namely CpMAX1a, CpMAX1b, and CpMAX1c. Quantitative real-time PCR (qRT-PCR) revealed the expression of CpMAX1a in all tissues, being highest in leaves, whereas CpMAX1b was only expressed in stems, while CpMAX1c was expressed in both roots and stem tips. However, CpMAX1a's expression decreased significantly after decapitation; hence, we verified its gene function. CpMAX1a was located in Arabidopsis chloroplasts. Overexpressing CpMAX1a restored the phenotype of the branching mutant max1−3, and reduced the rosette branch number, but resulted in no significant phenotypic differences from the wild type. Additionally, expression of AtBRC1 was significantly upregulated in transgenic lines, indicating that the CpMAX1a gene has a function similar to the homologous gene of Arabidopsis. In conclusion, our study shows that CpMAX1a plays a conserved role in regulating the branch development of wintersweet. This work provides a molecular and theoretical basis for better understanding the branch development of wintersweet.

Carotenoid Cleavage Dioxygenase Genes of Chimonanthus praecox, CpCCD7 and CpCCD8, Regulate Shoot Branching in Arabidopsis.

Strigolactones (SLs) regulate plant shoot development by inhibiting axillary bud growth and branching. However, the role of SLs in wintersweet (Chimonanthus praecox) shoot branching remains unknown. Here, we identified and isolated two wintersweet genes, CCD7 and CCD8, involved in the SL biosynthetic pathway. Quantitative real-time PCR revealed that CpCCD7 and CpCCD8 were down-regulated in wintersweet during branching. When new shoots were formed, expression levels of CpCCD7 and CpCCD8 were almost the same as the control (un-decapitation). CpCCD7 was expressed in all tissues, with the highest expression in shoot tips and roots, while CpCCD8 showed the highest expression in roots. Both CpCCD7 and CpCCD8 localized to chloroplasts in Arabidopsis. CpCCD7 and CpCCD8 overexpression restored the phenotypes of branching mutant max3-9 and max4-1, respectively. CpCCD7 overexpression reduced the rosette branch number, whereas CpCCD8 overexpression lines showed no phenotypic differences compared with wild-type plants. Additionally, the expression of AtBRC1 was significantly up-regulated in transgenic lines, indicating that two CpCCD genes functioned similarly to the homologous genes of the Arabidopsis. Overall, our study demonstrates that CpCCD7 and CpCCD8 exhibit conserved functions in the CCD pathway, which controls shoot development in wintersweet. This research provides a molecular and theoretical basis for further understanding branch development in wintersweet.

Green Enzyme-Linked Immunosorbent Assay Based on the Single-Stranded Binding Protein-Assisted Aptamer for the Detection of Mycotoxin.

In this work, a green enzyme-linked immunosorbent assay (ELISA) based on the single-stranded binding protein (SSB)-assisted aptamer was designed for biosensing applications. Combined with the biotin-streptavidin (SA) system and the high catalytic activity of horseradish peroxidase (HRP), this SSB-assisted aptamer sensor was applied for the detection of aflatoxin B1, ochratoxin A, and zearalenone. In this novel ELISA, mycotoxin-protein conjugations were replaced by SSB to avoid the hazard of mycotoxin, whereas antibodies were replaced by aptamer to avoid the complex and tedious preparation of antibodies. In the absence of target mycotoxins, SSB can bind the aptamer-biotin specifically. Detection was performed using the strong combination of biotin and SA after adding SA-HRP and substrate/chromogen solution, thereby resulting in a strong yellow color signal. In the presence of target mycotoxins, the aptamer-biotin cannot bind to the SSB, thereby leading to a weak yellow color signal. Under optimal conditions, the designed method was successfully applied for the determination of real sample and exhibited high specificity and low limits of detection in corn (112 ng L-1 for aflatoxin B1, 319 ng L-1 for ochratoxin A, and 377 ng L-1 for zearalenone). The green ELISA may also be extended to the detection of other biohazardous targets by changing the aptamer.

Using molecular descriptors for assisted screening of heterologous competitive antigens to improve the sensitivity of ELISA for detection of enrofloxacin in raw milk.

The use of the heterologous competitive strategy has become a vital method to improve the sensitivity of ELISA. In this work, we prepared an anti-enrofloxacin (ENR) mAb with ENR-bovine serum albumin (BSA) as immunogen. The molecular descriptors of quinolones were then used to screen heterologous coating antigens for the detection of ENR based on an ensemble learning method to improve the sensitivity of the ELISA. Results indicated that 6 of the 7 selected heterologous competitive antigens could enhance the sensitivity of ELISA. The ELISA sensitivity for the detection of ENR with sarafloxacin-BSA as heterologous coating antigen was improved 10-fold (in PBS) and 6-fold (in milk) compared with that with ENR-BSA as homologous antigen. The strategy can effectively screen suitable heterologous competitive antigens to improve the sensitivity of ELISA, followed by preparation of mAb with no additional modification to the corresponding immunogen.

Invited review: Advancements in lateral flow immunoassays for screening hazardous substances in milk and milk powder.

Dairy-related food safety outbreaks, such as food-borne pathogen contamination, mycotoxin contamination, and veterinary drug contamination, sometimes happen and have been reported all over the world, affecting human health and, in some cases, leading to death. Thus, rapid yet robust detection methods are needed to monitor milk and milk powder for the presence of hazardous substances. The lateral flow immunoassay (LFI) is widely used in onsite testing because of its rapidity, simplicity, and convenience. In this review, we describe some traditional LFI used to detect hazardous substances in milk and milk powder. Furthermore, we discuss recent advances in LFI that aim to improve sensitivity or detection efficiency. These advances include the use of novel label materials, development of signal amplification systems, design of multiplex detection systems, and the use of nucleic acid-based LFI.

CpWRKY71, a WRKY Transcription Factor Gene of Wintersweet (Chimonanthus praecox), Promotes Flowering and Leaf Senescence in Arabidopsis.

The WRKY transcription factors are one of the most important plant-specific transcription factors and play vital roles in various biological processes. However, the functions of WRKY genes in wintersweet (Chimonanthus praecox) are still unknown. In this report, a group IIc WRKY gene, CpWRKY71, was isolated from wintersweet. CpWRKY71 was localized to the nucleus and possessed transcriptional activation activity. qRT-PCR (quantitative real-time PCR) analysis showed that CpWRKY71 was expressed in all tissues tested, with higher expression in flowers and senescing leaves. During the flower development, the highest expression was detected in the early-withering stage, an obvious expression of CpWRKY71 was also observed in the flower primordia differentiation and the bloom stage. Meanwhile, the expression of CpWRKY71 was influenced by various abiotic stress and hormone treatments. The expression patterns of the CpWRKY71 gene were further confirmed in CpWRKY71pro:GUS (ß-glucuronidase) plants. Heterologous overexpression of CpWRKY71 in Arabidopsis caused early flowering. Consistent with the early flowering phenotype, the expression of floral pathway integrators and floral meristem identity (FMI) genes were significantly up-regulated in transgenic plants. In addition, we also observed that the transgenic plants of CpWRKY71 exhibited precocious leaf senescence. In conclusion, our results suggested that CpWRKY71 may be involved in the regulation of flowering and leaf senescence in Arabidopsis. Our study provides a foundation for further characterization of CpWRKY genes function in wintersweet, and also enrich our knowledge of molecular mechanism about flowering and senescence in wintersweet.

Lateral flow immunoassay integrated with competitive and sandwich models for the detection of aflatoxin M1 and Escherichia coli O157:H7 in milk.

Pathogens, mycotoxins, or antibiotics may exist in a food sample. Micro- and macromolecular substances must be detected quickly. A rapid and convenient lateral flow immunoassay (LFI) integrated with competitive and sandwich models was developed to detect micro- and macromolecular substances. In this study, aflatoxin M1 (AFM1) and Escherichia coli O157:H7 were selected as the micro- and macromolecular substances, respectively. Two test lines in the LFI test strip were evaluated to detect AFM1 and E. coli O157:H7 by competitive and sandwich models. Results showed that the limits of detection for detecting AFM1 and E. coli O157:H7 were 50 pg·mL-1 and 1.58 × 104 cfu·mL-1, respectively. The whole assay time was 30 min. The recoveries of gold nanoparticle-LFI ranged from 78.0 to 111.6% with coefficients of variation in the range of 3.9 to 8.5% for the detection of AFM1. For the detection of E. coli O157:H7, the range of recoveries was from 70.1 to 89.6% with coefficients of variation ranging from 4.9 to 13.0%. This study not only tested sensitivity and specificity, but also was a systematic study of location of 2 test lines of the LFI test strip integrated with competitive and sandwich models.

Floral Scent Emission from Nectaries in the Adaxial Side of the Innermost and Middle Petals in Chimonanthus praecox.

Wintersweet (Chimonanthus praecox) is a well-known traditional fragrant plant and a winter-flowering deciduous shrub that originated in China. The five different developmental stages of wintersweet, namely, flower-bud period (FB), displayed petal stage (DP), open flower stage (OF), later blooming period (LB), and wilting period (WP) were studied using a scanning electron microscope (SEM) to determine the distribution characteristics of aroma-emitting nectaries. Results showed that the floral scent was probably emitted from nectaries distributed on the adaxial side of the innermost and middle petals, but almost none on the abaxial side. The nectaries in different developmental periods on the petals differ in numbers, sizes, and characteristics. Although the distribution of nectaries on different rounds of petals showed a diverse pattern at the same developmental periods, that of the nectaries on the same round of petals showed some of regularity. The nectary is concentrated on the adaxial side of the petals, especially in the region near the axis of the lower part of the petals. Based on transcriptional sequence and phylogenetic analysis, we report one nectary development related gene CpCRC (CRABS CLAW), and the other four YABBY family genes, CpFIL (FILAMENTOUS FLOWER), CpYABBY2, CpYABBY5-1, and CpYABBY5-2 in C. praecox (accession no. MH718960-MH718964). Quantitative RT-PCR (qRT-PCR) results showed that the expression characteristics of these YABBY family genes were similar to those of 11 floral scent genes, namely, CpSAMT, CpDMAPP, CpIPP, CpGPPS1, CpGPPS2, CpGPP, CpLIS, CpMYR1, CpFPPS, CpTER3, and CpTER5. The expression levels of these genes were generally higher in the lower part of the petals than in the upper halves in different rounds of petals, the highest being in the innermost petals, but the lowest in the outer petals. Relative expression level of CpFIL, CpCRC, CpYABBY5-1, and CpLIS in the innermost and middle petals in OF stages is significant higher than that of in outer petals, respectively. SEM and qRT-PCR results in C. praecox showed that floral scent emission is related to the distribution of nectaries.

Comparison of 4 label-based immunochromatographic assays for the detection of Escherichia coli O157:H7 in milk.

Immunochromatographic assays (ICA) are widely used to detect pathogens. In this study, we used traditional gold nanoparticles (GNP), quantum dots (QD), fluorescent nanoparticles (FNP), and europium (Eu) (III) chelate nanoparticles (EuNP) as ICA labels. We first compared the ability of the 4 ICA test strips to quantitatively detect Escherichia coli O157:H7 in milk. We then optimized various parameters influencing the ICA. The sensitivity to E. coli O157:H7 of the GNP-ICA, QD-ICA, FNP-ICA, and EuNP-ICA was 2.5 × 104, 5 × 103, 1.0 × 103, and 5.0 × 102 cfu mL-1, respectively. The EuNP-ICA exhibited the highest sensitivity. The amounts of monoclonal antibodies (mAb) per GNP-ICA, QD-ICA, FNP-ICA, and EuNP-ICA test strip were 0.16, 0.37, 0.04, and 0.10 µg, respectively. The corresponding coefficients of variation were 7.4 to 15.8%, 10.4 to 18.6%, 2.7 to 7.8%, and 6.9 to 10.5%, respectively. The FNP-ICA required the least mAb per test strip and had the best coefficient of variation. The linear ranges of GNP-ICA, QD-ICA, FNP-ICA, and EuNP-ICA were 1.0 × 104 to 1.0 × 106, 2.5 × 103 to 1.0 × 106, 2.5 × 102 to 2.5 × 105, and 2.5 × 102 to 2.5 × 105 cfu mL-1, respectively. The FNP-ICA and EuNP-ICA had wider linear ranges than GNP-ICA and QD-ICA. Additionally, the FNP-ICA and EuNP-ICA showed better tolerance than GNP-ICA and QD-ICA in the milk samples. The FNP-ICA and EuNP-ICA showed remarkable potential for detection of pathogens in milk.