[Objective] To construct a recombinant food-and-mouth disease virus (FMDV) strain carrying the genes encoding three topotypes of immunodominant structural proteins of serotype O FMDV by reverse genetic manipulation and evaluate the potential of the recombinant strain serving as a vaccine candidate for porcine food-and-mouth disease (FMD) type O. [Methods] Based on the gene of the recombinant FMDV with the replacement of the VP1 structural protein of O/NXYCh/CHA/2018 epidemic strain, the recombinant full-length plasmid featuring substitution of G-H loop genes of the structural protein VP1 of O/TUR/5/2009 vaccine strain was constructed by gene synthesis. The recombinant virus was rescued after transfection of the linearized recombinant plasmid into BSR/T7 cells expressing T7 RNA polymerase, and then identified by RT-PCR, sequencing, and indirect immunofluorescence. The plaque assay and one-step growth curve building were employed to characterize the recombinant virus. Pigs were vaccinated with the vaccines prepared from the recombinant virus and the parental virus, and then virus neutralization tests were carried out to examine the cross-reactive responses against the epidemic serotype O FMDV isolates of three topotypes. [Results] The recombinant FMDV strain carrying the structural protein genes of three topotypes was successful rescued. The recombinant strain showed similar biological properties to the parental virus. Pigs vaccinated with the vaccines prepared from the recombinant virus and the parental virus produced protective neutralizing antibodies with the mean titer of > 1.65log₁₀ against the viruses of the Middle East-South Asia (ME-SA) and South-East Asia (SEA) topotypes. The pigs did not produce protective neutralizing antibodies against the Cathay topotype (< 1.65log₁₀). The substitution of O/TUR/5/2009 G-H loop gene improved the cross-reactivity against the viruses of ME-SA and SEA topotypes compared with the parental virus (P < 0.05). [Conclusion] This study has guiding significance for the design of FMD vaccines in the future.

Since the formation of a committee under the guidance of R. E. Buchanan in 1936, microbiologists have developed and refined a nomenclatural code for bacteriology, the International Code of Nomenclature of Prokaryotes (ICNP). This code has greatly facilitated recent advances in taxonomy and related fields of microbiology. Technical developments in omics have led to a surge in genome-based discoveries of novel uncultured species, many of which play important roles in environmental and medical microbiology. Nevertheless, the ICNP only recognizes cultures as nomenclatural types, thereby preventing the names of the uncultured microorganisms from being validly published. To compensate for the ineffectiveness of the ICNP in creating permanent and stable names of uncultured taxa, the Code of Nomenclature of Prokaryotes Described from Sequence Data (SeqCode) was published in 2022. The SeqCode was formed with the intention of complementing and someday merging with the ICNP. However, as the two nomenclatural codes currently work independently, the consequences of the concurrence of both codes on the scientific community are still not clear. Here, we introduce the histories and principles of the ICNP and SeqCode, summarize their advantages and limitations, and call for scholars to both respect and utilize the two nomenclatural codes of prokaryotes, aiming to facilitate the establishment of a more reasonable and beneficial naming system.

Food allergy (FA) with growing incidence has emerged as one of the public health problems around the world as it seriously affects the life quality of children. Recent studies have discovered that there are significant differences in the composition of gut microbiota between the children with FA and healthy children. In-depth studies have reported that gut microbiota can help to maintain immune balance by regulating immune cells such as dendritic cells, helper T cells, regulatory T cells, mastocytes, and granulocytes. In addition, gut microbiota can enhance the intestinal barrier function to inhibit FA in a variety of ways. On the basis of research results from animal experiments, probiotics and prebiotics have been used in the treatment of FA in children, whereas the effect is not ideal. As FA occurs in a growing number of children in the world, this article reviews some mechanisms of gut microbiota in influencing FA and summarizes the application of probiotics and prebiotics in the treatment and prevention of FA in children in recent years. Furthermore, this article proposes new ideas for deciphering the mechanism of gut microbiota in regulating FA and applying probiotics and probiotic metabolites in the treatment and prevention of FA in children, which is of great significance for promoting the research on the treatment of FA in children.

[Objective] To explore the effect and mechanism of the antimicrobial peptide CATH-B1 on extraintestinal pathogenicEscherichia coli (RS218)-induced inflammatory response in microglia. [Methods] We used RS218-infected mouse microglial BV2 cells as the inflammation modelin vitro and set three groups: Mock, RS218 infection, and CATH-B1 pretreatment+RS218 infection. The Cell Counting Kit-8 (CCK-8) was used to determine cell viability. The colony counting assay was used to examine the growth, adhesion, and invasion of bacterial cells. Enzyme linked immunosorbent assay (ELISA) was employed to determine the concentrations of interleukin (IL)-1β, IL-6, IL-12, and tumor necrosis factor (TNF)-α in the supernatant of cell culture. Quantitative real-time PCR (RT-PCR) was performed to determine the mRNA levels of IL-1β and IL-6. Western blotting was employed to determine the protein levels of nuclear factor-kappa B (NF-κB) P65, the mitogen-activated protein kinase (MAPK) extracellular signal-regulated kinase (ERK), and their phosphorylated forms. [Results] CATH-B1 inhibited the RS218-induced secretion of IL-1β, IL-6, and IL-12 and mRNA expression of IL-1β and IL-6. However, CATH-B1 did not affect bacterial adhesion or invasion. In addition, CATH-B1 inhibited the expression of phosphorylated P65 and ERK. [Conclusion] CATH-B1 plays a vital role in reducing inflammation by inhibiting the activation of NF-κB and MAPK signaling pathways. The finding provides a basis for elucidating the mechanism of antimicrobial peptides against neuroinflammation.

Botulinum neurotoxins (BoNTs), a group of the most toxic proteins, can cause muscle paralysis and even lead to death in severe cases. BoNTs can be classified into 7 serotypes (BoNT/A−BoNT/G) and further classified into more than 40 subtypes according to the differences in amino acid sequences. BoNTs consist of three basic domains: the C-terminal receptor-binding domain of the heavy chain, the N-terminal translocation domain, and the light-chain catalytic domain. On the surface of motor neurons, the receptor-binding domain binds first to polysialoganglioside and subsequently to synaptic vesicle protein 2 or synaptotagmin to form a two-receptor complex. The functioning of each serotype relies on the binding of the receptor-binding domain to the corresponding receptor. BoNTs have always been a research hotspot in terms of the structure, function, and effect on the host. The role of the receptor-binding domain in promoting the specific binding of BoNTs to motor neurons has become a new research direction. This review summarizes the structural changes of the receptor-binding domains and the differences in binding sites during the binding of different serotypes of BoNTs to receptors. By analyzing the sequences and structural characteristics of the receptor-binding domains of different serotypes and subtypes, we can fully understand the sequence differences and functions of the receptor-binding domain and give insights into the treatment of BoNTs.

[Objective] As an important coenzyme in human body, coenzyme Ⅰ (nicotinamide adenine dinucleotide, NAD⁺) plays an important role in maintaining cell growth, differentiation, and energy metabolism and protecting cells. Reduced nicotinamide mononucleotide (NMNH), an effective NAD⁺ enhancer, can efficiently elevate the levels of NAD⁺ in tissues. NADH pyrophosphatase can transform reduced nicotinamide adenine dinucleotide (NADH) into NMNH to promote the regeneration of NAD⁺. The purpose of this study is to construct a NADH pyrophosphatase expression system inBacillus subtilis and realize the synthesis of NMNH by biotransformation. [Methods] NADH pyrophosphatase was successfully expressed inB.subtilis WB600 by vector screening, and promoter engineering was employed to improve the enzyme activity. Furthermore, the industrial application potential of the recombinant enzyme was further investigated by medium optimization and amplified fermentation in a 5 L fermenter. On this basis, the whole cell catalytic system was used for biotransformation to synthesize NMNH. [Results] The initial activity of NADH pyrophosphatase and the yield of NMNH were 1.70 U/mL and 135 mg/L, respectively. After promoter engineering, the enzyme activity was improved by 41%. In addition, the enzyme activity was increased to 5.02 U/mL after optimization of the culture medium and amplified fermentation in a 5 L fermenter, which was 1.09 times higher than that in a shake flask. On this basis, the whole-cell catalytic system was used for biotransformation, and the yield of NMNH reached 1.20 g/L, which was 7.75 times higher than the initial yield. [Conclusion] We built an efficient expression system of NADH pyrophosphatase inB.subtilis and realized the efficient transformation from NADH to NMNH by whole-cell catalysis, providing a new idea for the biosynthesis of NMNH.

[Objective] To develop a stable and controllable method for isolating and cultivating the eukaryotic microorganismEntodiniumcaudatum from the rumen of ruminants, which would lay a foundation for the germplasm banking and provide sufficient experimental materials for researching the physiological function of rumen ciliates. [Methods] First, a rumen cannula was used to collect rumen fluid from cows in Wuhan, andE.caudatum was gradually enriched and isolated from the rumen fluid by micro-strainer filtration through different sizes of nylon mesh. Subsequently, the enrichedE.caudatum was cultured in anaerobic culture bottles loaded with the modified SP medium. After purification, a single culture of the strain was established. The species was identified by morphological observation and the phylogenetic analysis based on the 18S rRNA gene. Finally, the generation time of theE.caudatum was calculated based on the half-transfer cultivation method. [Results] A single culture ofE.caudatum was isolated from the rumen fluid of Holstein cows. The modified SP medium used in this study was composed of SP salt solution, supernatant of the rumen fluid without protozoa, cysteine hydrochloride, antibiotics, starch, and grass powder. In the modified SP medium, the obtained culture grew and proliferated steadily, reaching the highest density of 37 000 cells/mL on day 16 from the initial inoculation density of 320 cells/mL. Morphological features and molecular data indicated that the culture obtained in this study wasE.caudatum, namedE.caudatum strain WH. The generation time ofE.caudatum strain WH was 19.0 h. [Conclusion] This study has successfully developed aninvitro cultivation method forE.caudatum strain WH, a prevalent eukaryotic microorganism from the rumen of ruminants. This work lays a technical and theoretical basis for the germplasm banking and in-depth research on the physiological functions of rumen ciliates.

[Objective] To clarify the promotion effects of different organic compounds on the formation of magnetosomes inAcidithiobacillus ferrooxidans BYM, so as to provide a new idea for safely and effectively improving the magnetosome yield. [Methods] Single-factor experiments were conducted to measure the effects of ten organic compounds on the ferrous oxidation ofA.ferrooxidans BYM, and the organic compounds promoting the synthesis of magnetosomes were further screened by a 4 L fermentation system. The classical kinetic models (Logistic, Luedeking-Piret, and substrate consumption kinetic equations) were employed to build the kinetic models for the growth, magnetosome synthesis, and ferrous consumption ofA.ferrooxidans BYM by batch fermentation experiments. [Results] The maximum magnetosome yield (2.00×10⁻³ g/L) was achieved with the addition of 10 mmol/L gluconic acid, in the presence of which the bacterial cells were oval and had a smooth surface. With the addition of gluconic acid, the fermentation kinetics ofA.ferrooxidans BYM was in accordance with Logistic, Luedeking-Piret, and substrate consumption kinetic equations. [Conclusion] The addition of 10 mmol/L gluconic acid increases the magnetosome yield ofA.ferrooxidans BYM by eight times. Gluconic acid changes the cell morphology and surface ofA.ferrooxidans BYM. The kinetics models of cell growth, product formation, and substrate consumption can illustrate the batch fermentation ofA.ferrooxidans BYM in the presence of gluconic acid.

[Objective] Selenium (Se) is an essential trace element playing a critical role in maintaining the physiological metabolism of humans. Among its various forms, selenium nanoparticles (SeNPs) possess higher bioavailability and lower toxicity. The study aims to screen a probiotic strain that can efficiently synthesize SeNPs from selenite. [Methods] Lacticaseibacillus paracasei SCFF20 capable of converting sodium selenite to SeNPs was screened out from 14 strains of probiotics. The SeNPs produced byL.paracasei SCFF20 were purified, freeze-dried, and systematically characterized by scanning electron microscopy coupled with energy-dispersive X-ray (SEM-EDX), dynamic light scattering (DLS), X-ray diffractometer (XRD), Raman spectroscopy, and Fourier transform infrared spectroscopy (FTIR). [Results] SEM-EDX results revealed that Se was the primary constituent of SeNPs. The synthesized SeNPs were spherical and polydisperse, with an average particle size of 500.62 nm. XRD and Raman spectroscopy confirmed that the SeNPs were amorphous. Additionally, FTIR demonstrated the presence of proteins, exopolysaccharides, and lipids coating the surface of the SeNPs. Moreover, the reduction rate of SeNPs was determined to be 91.42% by inductively coupled plasma-optical emission spectroscopy (ICP-OES). [Conclusion] The findings of this study highlight the potential ofL.paracasei SCFF20 as a probiotic strain capable of producing SeNPs. The strain can be used as a cell factory for the safe production of biogenic SeNPs as nutritional supplements and functional food.

[Objective] High-temperature stacking fermentation is a key process in the production of Jiang-flavor Baijiu.Kroppenstedtia is a predominant bacterial genus in the stacked fermented grains, and investigating its growth and metabolic characteristics contributes to comprehensively understanding the crucial role of stacking fermentation. [Methods] The tryptic soy broth was used to screenKroppenstedtia strains from the stacked fermented grains, and the taxonomic status of each strain was determined by morphological observation and 16S rRNA gene sequencing. Furthermore, the growth characteristics and volatile compound metabolism of each strain were investigated by solid-state fermentation experiments on sorghum at different temperatures (45 ℃ and 50 ℃) in combination with pure culture. [Results] Three strains ofKroppenstedtia were isolated from the fermented grains of Jiang-flavor Baijiu and identified asK.eburnea. The liquid culture of strainK.eburnea 1613 significantly enhanced the production of pyrazines, which was 2.66 folds of that in the control group. The volatile compounds of sorghum in solid-state fermentation predominantly consisted of alcohols and acids, the total content of which increased over the fermentation time. The fermentation at 50 ℃ promoted the accumulation of alcohols, acids, and pyrazines, and that at 45 ℃ facilitated the accumulation of esters. The primary metabolites produced by the three strains during solid-state fermentation with sorghum as the substrate were phenethyl alcohol and isovaleric acid. The fermentation withK.eburnea 1615 at 50 ℃ for 15 days produced the highest levels of phenethyl alcohol and isovaleric acid, which reached (31.17±0.14) µg/g and (16.75±0.76) µg/g, respectively. The fermentation withK.eburnea 6E22 andK.eburnea 1613 at 50 ℃ yielded the highest levels of 2, 5-dimethyl pyrazine [(1.67±0.14) µg/g] and hexanoic acid [(3.74±0.19) µg/g], respectively, after 15 days. The accumulation of aldehydes and ketones was significant in sorghum fermented at 50 ℃. The partial least squares-discriminant analysis (PLS-DA) revealed significant influences of temperature and time on the volatile compound composition of sorghum fermented by the three strains. [Conclusion] K.eburnea contributes to the production of flavor compounds in fermented grains, particularly the characteristic flavor compounds such as alcohols, acids, and pyrazines of Jiang-flavor Baijiu.