Enhanced protective effect of selenium-biofortified peptide RYNA(Se)MNDYT compared with its native peptide RYNAMNDYT in lipopolysaccharide-injured murine gut microbiota

Selenopeptides may be a valuable bioactive compound to promote gut microbiota-targeted therapeutic methods for intestinal disease and hepatopathy.However,limited information is available on the utilization of selenopeptides by gut microbiota,especially Selenium(Se)function.For this purpose,the present study aimed to investigate the protective effect of selenopeptide(RYNA(Se)MNDYT,Se-P2,purity of≥95%)and its original peptide(RYNAMNDYT,P2,purity of≥95%)in vivo by the microbiota-metabolite axis and further analyze the potential contribution of Se biofortification to Se-P2 bioactivity.The results showed that Se-P2 exhibits a higher protective effect on lipopolysaccharide(LPS)-induced inflammation than P2,including pathology of the colon and liver,which suggested that the bioactivity of P2 was promoted by the organic combination of Se.Notably,gut microbiota composition tended to be a healthy structure by Se-P2 pretreatment in LPS-injured mice,which had a positive effect on LPS-induced gut microbiota dysbacteriosis.Additionally,only Se-P2 promoted an increase in the relative abundance of Lactobacillus,Alistipes,and Roseburia and a decrease in the relative abundance of Akkermansia,Erysipelatoclostridium,and Bacteroides in LPS-injured mice.The changes in gut microbiota were obviously correlated with the changes in metabolites and affected the metabolic pathways of valine,leucine,isoleucine,phenylalanine,tyrosine,and tryptophan biosynthesis and phenylalanine metabolism.This may be one of the key reasons for Se-P2 to exert bioactivity through the microbiota-metabolite axis.Furthermore,Se-biofortification in Se-enriched Cordyceps militaris affected the parental proteins of Se-P2 to modulate mitogen-activated protein kinase,GPI anchored protein,and carbohydrate metabolism,translation,folding,sorting and degradation,which may contribute to the bioactivity of Se-P2.Our study provides information on the effect of Se on selenopeptides in vivo,which further promotes the prospective applications of selenopeptides as dietary supplements.

Insights into Cronobacter sakazakii Biofilm Formation and Control Strategies in the Food Industry

Cronobacter sakazakii(C.sakazakii)is a foodborne opportunistic pathogen that can cause life-threatening invasive diseases,such as necrotizing enterocolitis,meningitis,and sepsis in infants.The potential risk of C.sakazakii contamination of powdered infant formula(PIF)is an issue that has attracted considerable attention from manufacturers,regulators,and consumers.C.sakazakii biofilms on the surfaces of equipment and in diverse food-production environments constitute a mode of cell growth that protects the pathogen from hostile environments,and are an important source of persistent contamination of food products.Bacterial biofilms are difficult to remove due to their resistant properties.Conventional cleaning and sterilizing procedures may be insufficient for biofilm control,and may lead to further biofilm development and dispersal.Consequently,novel control strategies are being developed,such as nanotechnology-based delivery systems,interspecies interactions,antimicrobial molecules of microbial origin,natural extracts,and phages.This review focuses on describing the mechanisms underlying the biofilm formation and behavior of C.sakazakii and discussing potential control strategies.

Food Safety Risks and Contributing Factors of Cronobacter spp.

Cronobacter species are a group of Gram-negative opportunistic pathogens,which cause meningitis,sep-ticemia,and necrotizing enterocolitis in neonates and infants,with neurological sequelae in severe cases.Interest in Cronobacter has increased significantly in recent years due to its high virulence in children.In this review,we summarize the current understanding of the prevalence of Cronobacter species in several important food types.We discuss the response mechanisms enabling persistence in adverse growth con-ditions,as well as its pathogenicity.We emphasize the food safety concerns caused by Cronobacter and subsequent control methods and clinical treatments.

Quantum Dot Nanobeads-Labelled Lateral Flow Immunoassay Strip for Rapid and Sensitive Detection of Salmonella Typhimurium Based on Strand Displacement Loop-Mediated Isothermal Amplification

Rapid,sensitive,point-of-care detection of pathogenic bacteria is important for food safety.In this study,we developed a novel quantum dot nanobeads-labelled lateral flow immunoassay strip(QBs-labelled LFIAS)combined with strand displacement loop-mediated isothermal amplification(SD-LAMP)for quantitative Salmonella Typhimurium(ST)detection.Quantum dot nanobeads(QBs)served as fluorescence reporters,providing good detection efficiency.The customizable strand displacement(SD)probe was used in LAMP to improve the specificity of the method and prevent by-product capture.Detection was based on a sandwich immunoassay.A fluorescence strip reader measured the fluorescence intensity(FI)of the test(T)line and control(C)line.The linear detection range of the strip was 10^(2)–10^(8) colony forming units(CFU)·mL^(-1).The visual limit of detection was 10^(3) CFU·mL^(-1),indicating that the system was ten-fold more sensitive than AuNPs-labelled test strips.ST specificity was analyzed in accordance with agarose gel outputs of polymerase chain reaction(PCR)and SD-LAMP.We detected ST in foods with an acceptable recovery of 85%–110%.The method is rapid,simple,almost equipment-free,and suitable for bacterial detection in foods and for clinical diagnosis.

CO activation by the heterobinuclear transition metal-iron clusters: A photoelectron spectroscopic and theoretical study

Spectroscopic characterization of CO activation on multiple metal-containing catalysts remains an important and challenging goal for identifying the structure and nature of active site in many industrial processes such as Fischer-Tropsch chemistry and alcohol synthesis.Here,we use mass-selected photoelectron velocity-map imaging spectroscopy and quantum chemical calculations to study the reactions of CO molecules with several heterobinuclear transition metal-iron clusters M-Fe(M=Ti,V,Cr).The mass spectra reveal the favorable formation of MFe(CO)_(4)^(-)with relatively high thermodynamic stability.The MFe(CO)_(4)^(-)(M=Ti,V,Cr) complexes are established to have a metal-Fe bonded M-Fe(CO)_(4) structure with C_(3 v) geometry.While the positive charge and unpaired electrons are mainly located on the M atom,the natural charge of Fe(CO)_(4) is about-2 e.The MFe(CO)_(4)^(-)(M=Ti,V,Cr) can be seen as being formed via the interactions between the M^(+)fragment and the [Fe(CO)_(4)]^(2-)core,which satisfies the 18-electron rule.The CO molecules are remarkably activated in these MFe(CO)_(4)^(-).These results shed insight into the structure-reactivity relationship of heterobinuclear transition metal carbonyls and would have important implications for understanding of CO activation on alloy surfaces.

副溶血性弧菌生物被膜形成及其调控机制研究进展

副溶血性弧菌是一种广泛存在于海产品中并可引起人类急性肠胃炎的食源性致病菌。该菌形成的生物被膜能够增强体外环境中的存活率,促进对宿主的定殖和感染,还会导致被污染的加工设备与食物之间发生交叉感染。深入了解生物被膜形成背后的调控机制,有助于制定有针对性的策略,干扰其适应环境变化的过程,从而降低副溶血性弧菌对人类的危害。本文主要综述了鞭毛、菌毛和胞外的多糖等基质组分在生物被膜形成中的作用以及c-di-GMP和群体感应对生物被膜形成的调控。

整合子系统介导沙门菌耐药性的研究进展

沙门菌(Salmonella spp.)是公共卫生学上具有重要意义的人畜共患病病原菌。人、畜感染沙门菌后会引起伤寒、副伤寒、胃肠炎、败血症和肠外局灶性感染等疾病。抗生素是治疗沙门菌严重感染的有效手段,随着临床和畜牧业中抗生素的大量使用,使得沙门菌的耐药情况日益严重。整合子是普遍存在于细菌中的一种可移动基因元件,可有效捕获外源基因确保其表达,并复合于转座子、质粒等,使多种耐药基因在细菌种内或者种间进行传播。在过去的二十年中,随着新基因盒和复杂整合子的不断出现,导致整合子系统迅速进化。整合子在沙门菌耐药性传播过程中具有非常重要的作用,因此,本文对整合子系统的分子结构、分类、作用机制,以及沙门菌中存在的Ⅰ、Ⅱ、Ⅲ类整合子介导的耐药性及现有检测方法的研究进展进行综述,以期为沙门菌耐药性研究提供参考。

Supplementation with high-GABA-producing Lactobacillus plantarum L5 ameliorates essential tremor triggered by decreased gut bacteria-derived GABA

Background Theγ-aminobutyric acid(GABA)hypothesis posits a role of GABA deficiency in the central nervous system in the pathogenesis and progression of essential tremor(ET).However,the specific causative factor for GABA deficiency is not clear.The gut microbiota in mammals has recently been considered as a significant source of GABA.Furthermore,the GABA-based signals originating from the intestine can be transmitted to the brain through the“enteric nervous system-vagus nerve-brain”axis.However,the plausible contribution of gut microbiota to ET seems inspiring but remains obscure.Methods Fecal samples from patients with ET and healthy controls were examined by metagenomic sequencing to compare the composition of gut microbiota and the expression of genes involved in GABA biosynthesis.The impact of gut microbiota on ET was explored through transplantation of fecal microbiota from patients with ET into the murine ET model.Lactic acid bacteria producing high amounts of GABA were identified through whole-genome sequencing and ultra-performance liquid chromatography-tandem mass spectrometry.Subsequently,mice were treated with the high-GABA-producing strain Lactobacillus plantarum L5.Tremor severity,behavioral tests,pro-inflammatory cytokines,GABA concentration,and gut microbiota composition were examined in these mice.Results The gut microbiota of patients with ET demonstrated an impaired GABA-producing capacity and a reduced fecal GABA concentration.Transplantation of the gut microbiota from patients with ET induced an extension of tremor duration and impaired mobility in the murine model of ET.L5 exhibited an augmented GABA-producing capacity,with the De Man-Rogosa-Sharpe culture broth containing 262 mg/l of GABA.In addition,administration of L5 significantly decreased the tremor severity and enhanced the movement capability and grasping ability of ET mice.In vivo mechanistic experiments indicated that L5 reshaped the gut microbial composition,supplemented the mucosa-associated microbiota with GABA-producing capacity,increased the GABA concentrations in the cerebellum,and diminished inflammation in the central nervous system.Conclusions These findings highlight that deficiency of GABA-producing gut microbes plays an essential role in the pathogenesis of ET and that L5 is a promising candidate for treating ET.

Photoelectron imaging spectroscopic signatures of CO activation by the heterotrinuclear titanium-nickel clusters

A series of heterotrinuclear Ti_(2)Ni(CO)_(n)^(-)(n=6-9)carbonyls have been generated via a laser vaporization supersonic cluster source and characterized by mass-selected photoelectron velocity-map imaging spectroscopy.Quantum chemical calculations have been carried out to identify the structures and understand the experimental spectral features.The results indicate that a building block of Ti-Ti-Ni-C four-membered ring with the C atom bonded to Ti,Ti,and Ni is dominated in the n=6-8 complexes,whereas a structural motif of Ti-Ti-Ni triangle core is preferred in n=9.These complexes are found to be capable of simultaneously accommodating all the main modes of metal-CO coordination(i.e.,terminal,bridging,and side-on modes),where the corresponding mode points to the weak,moderate,high C-O bond activation,respectively.The number of CO ligands for a specific bonding mode varies with the cluster size.These findings have important implications for molecular-level understanding of the interaction of CO with alloy surfaces/interfaces and tuning the appropriate CO activation via the selection of different metals.

CO oxidation on the heterodinuclear tantalum-nickel monoxide carbonyl complex anions

The series of heterodinuclear metal oxide carbonyls in the form of TaNiO(CO)_(n)(n=5-8) are generated in the pulsed-laser vaporization source and characterized by mass-selected photoelectron velocity-map spectroscopy.During the consecutive CO adsorption,the μ^(2)-O-bent structure initially is the most favorable for TaNiO(CO)_(5),and subsequently both μ^(2)-O-bent and μ^(2)-O-linear structures are degenerate for TaNiO(CO)_(6),then the μ^(2)-O-linear structure is most preferential for TaNiO(CO)_(7),and finally the η^(2)-CO_(2)-tagged structure is the most ene rgetically competitive one for TaNiO(CO)_(8),i.e., the CO oxidation occurs at n=8.ln contrast to the literature reported CO oxidation on heteronuclear metal oxide complexes generally proceeding via Langmuir-Hinshelwood-like mechanism,complementary theo retical calculations suggest that both Langmuir-Hinshelwood-like and Eley-Rideal-like mechanisms prevail for the CO oxidation reaction on TaNiO(CO)_(8) complex.Our findings provide new insight into the composition-selective mechanism of CO oxidation on heteronuclear metal complexes,of which the composition be tailored to fulfill the desired chemical behaviors.