Traditional Chinese Baijiu products can be classified into multiple flavor types such as strong-flavor, light-flavor, soy sauce-flavor, and complex-flavor types. Due to differences in fermentation raw materials, starters, fermentation vessels, fermentation processes, and geographical environments, Baijiu products of different flavor types have unique and complex pit-mud microorganisms. As one of the core microbial groups in the complex microbial community of Baijiu, lactic acid bacteria, whose metabolites lactic acid and its derivatives are important flavor substances in strong-flavor Baijiu, play an important role in the flavor and taste of Baijiu. At present, the research on lactic acid bacteria in the brewing of strong-flavor Baijiu is scattered and not systematic enough. On the basis of our work, we review the research on the role of lactic acid bacteria in the brewing of strong-flavor Baijiu. This review encompasses the isolation and screening of lactic acid bacteria in the brewing of strong-flavor Baijiu by conventional microbiological methods and the in-depth understanding of the role of lactic acid bacteria in the brewing of strong-flavor Baijiu by modern microbiological research methods. Combining traditional with modern microbiological research methods to conduct systematic and in-depth research on lactic acid bacteria in strong-flavor Baijiu based on actual strains can provide references for deeply understanding the role of lactic acid bacteria in the brewing process and then strengthening or optimizing the brewing process.

Shikimic acid (SA) is an important natural compound with many biological activities, including antiviral, antithrombotic, analgesic, antimicrobial, and anti-cancer properties. Due to its diverse applications in medicine, cosmetics, food, and agriculture, SA is considered a highly promising biomolecule. As a precursor of aromatic compounds, SA plays a crucial role in various metabolic pathways within organisms. Traditional methods for producing SA mainly rely on plant extraction (such as star anise) or chemical synthesis. However, these approaches face challenges such a high costs, low efficiency, and environmental concerns. With the ongoing advancements in synthetic biology and metabolic engineering, the production of SA through metabolic engineering has emerged as a focal point of research, offering a more sustainable and cost-effective alternative. This paper reviews the applications and production methods of SA, with a particular emphasis on recent progress and optimization strategies in its biosynthesis.

Streptococcus suis, a major pathogen of pigs, can cause meningitis, septicemia, and arthritis, leading to serious economic losses in the pig industry. In addition, it can also infect humans and result in diseases or death, being a zoonotic pathogen. Therefore, accurate, rapid, sensitive, and simple detection methods are critical for the prevention and control of swine streptococcosis. At present, a variety of detection methods for S. suis have been developed, including traditional detection methods of microbiology, molecular biology, and immunology and emerging technologies such as nanomaterial-based immunosensors, CRISPR-Cas12a system, and matrix-assisted laser desorption ionization-time of flight mass spectrometry. This review summarizes the principles, applications, advantages, and disadvantages of the above methods and introduces the future directions of S. suis detection methods, aiming to provide reference for the prevention and control of swine streptococcosis.

[Objective] To develop a DNA vaccine by loading avian pathogenic Escherichia coli ghosts with the fimbrium gene flfA of Gallibacterium anatis and evaluate the immune effect of this vaccine in chickens. [Methods] Taking flfA of G. anatis as the target gene, we constructed the eukaryotic expression plasmid pCAGGS-flfA from the plasmid pCAGGS-HA carrying the chicken β-actin promoter, which enhanced the efficacy of vaccine. The temperature-sensitive plasmid PBV-E-SN was then constructed and transformed into the ampicillin-sensitive avian pathogenic E. coli isolate to prepare a bacterial ghost. Finally, pCAGGS-flfA was loaded into the bacterial ghost to prepare a bacterial ghost vaccine. Seven-day-old chickens were assigned into five groups: bacterial ghost loading pCAGGS-flfA, pCAGGS-flfA, empty bacterial ghost, PBS, and normal control. The primary vaccination was carried out for 7-day-old chickens, and the booster immunization was performed two weeks after the primary immunization. The chickens were challenged with G. anatis four weeks after the primary immunization, and the immune effect of the vaccine was evaluated. [Results] The eukaryotic expression plasmid pCAGGS-flfA was successfully expressed in cells in vitro. The lysis rate of the constructed avian pathogenic E. coli ghosts heated at 42 °C for 210 min reached 99.94%. The specific IgG antibody titer measured by ELISA, the number of shedding bacteria in chicken cloacal swabs and throat swabs, and the bacterial loads in tissue and organs of challenged chickens showed that the immune effects in the bacterial ghost loading pCAGGS-flfA group and the pCAGGS-flfA group were much higher than those in other groups. Moreover, the bacterial ghost loading pCAGGS-flfA showed stronger immune effect than pCAGGS-flfA. [Conclusion] Bacterial ghosts as the carriers of pCAGGS-flfA significantly enhanced the immune effect of the DNA vaccine.

[Objective] To elucidate the phylogenetic position and mine the gene resources for synthesis of secondary metabolites from Streptomyces sp. YH02, a Gram-positive actinomycete strain isolated from the soil sediment of Yuncheng Salt Lake in Shanxi. [Methods] Illumina and PacBio platforms were used for whole genome sequencing of YH02, which was followed by gene prediction, functional annotation, prediction of secondary metabolite synthetic gene clusters (BGCs), comparative genomic analysis, and morphological, physiological, and biochemical characterization. [Results] The YH02 genome was a linear chromosome spanning 8 285 116 bp, with the G+C content of 71.77% and 7 237 open reading frames. Gene annotations in the GO, COG, KEGG, and CAZy identified 2 829, 5 478, 4 805, and 279 genes, respectively. The subcellular localization analysis predicted various secretion system-related proteins and 1 030 transporters. Additionally, 32 secondary metabolite BGCs were predicted in strain YH02, involving the synthesis of various natural products such as terpenoids, non-ribosomal peptides, polyketides, and ribosomally synthesized and post-translationally modified peptides. The comparative genomic analysis revealed 15 739 pan-genome orthologous gene clusters and 4 267 core genome orthologous gene clusters. The phylogenetic analysis based on the 16S rRNA gene sequence revealed a proximate phylogenetic affiliation between strain YH02 and Streptomycesvenezuelae ATCC 10712 as well as Streptomyceszaomyceticus NBC 00278. However, the average nucleotide identity (ANI) value was below the threshold of 95.00%, and the digital DNA-DNA hybridization (dDDH) value was less than 70.00%. YH02 exhibited light pink aerial mycelia on the ISP 2 medium. It showed significant differences in tolerance to pH, sodium chloride, and growth temperature compared with its closely related strains. Additionally, this strain demonstrated weak starch hydrolysis activity, positive gelatin liquefaction, positive nitrate reduction, and slow milk coagulation. [Conclusion] Based on the findings from genomic, physiological, and biochemical analyses, strain YH02 is confirmed as a potential new species of Streptomyces. This study not only enriches the microbial resource pool but also provides a theoretical basis and potential genetic resources for mining the natural products with unique mechanisms of action.

In the post-antibiotic era, phage therapy becomes a candidate for treating drug-resistant bacteria. Phages are diverse, and jumbo phages are a class of phages with genomes longer than 200 kb. Their large genomes carry abundant functional genes with scattered distribution. Jumbo phages have a variety of unique biological characteristics, such as oversized phage particles, unique replication cycles, and unique structures such as the nucleus-like compartment, the “inner body”, and the long-wavy curly tail fiber. This paper reviews the research progress in jumbo phages, focusing on their biological characteristics, genomes, evolution, and special replication mechanisms and structures. Furthermore, this review explores the application potential of jumbo phages in the treatment of drug-resistant bacterial infection, environmental management, aquaculture, and biocontrol, aiming to provide reference and implications for the research and application of jumbo phages.

[Objective] To explore the effects of freeze-thaw on oat silage during the aerobic exposure stage. [Methods] Oat silage was stored at a constant temperature (20 ℃, group 20, control) and freeze-thaw conditions (20 ℃ and -5 ℃ alternating every 12 h, group S) for 60 days and then subjected to aerobic exposure. Samples were collected on day 60 of ensiling and after aerobic exposure for 1, 3, and 5 days, respectively, for the determination of fermentation quality and nutritional quality as well as for 16S rRNA gene and ITS sequencing. [Results] The pH rose as the aerobic exposure was prolonged. The samples subjected to aerobic exposure at room temperature showed more rapid increases in ammonia nitrogen content and pH and more rapid decreases in lactic acid and acetic acid content than those subjected to aerobic exposure at freeze-thaw temperatures. Propionic acid and butyric acid were produced more rapidly in the S group, especially in the case of aerobic exposure at room temperature. Enterobacteria and yeast increased while lactic acid bacteria decreased as the aerobic exposure was prolonged (P<0.05). Shannon and Simpson indices of bacteria increased during aerobic exposure, and the relative abundance of lactic acid bacteria kept decreasing. The bacterial community structure presented a significant difference on days 3 of aerobic exposure, and microbial succession was accelerated by aerobic exposure at room temperature compared with that at the freeze-thaw temperature, with more species and higher counts of yeast and molds indicative of spoilage in the S group. [Conclusion] Freeze-thaw accelerated aerobic deterioration, especially aerobic exposure at room temperature. This study provides theoretical guidance for high-quality modulation and storage of oat silage in alpine areas.

[Objective] Mumps virus (MuV) is the causative agent of mumps. Nowadays, genotype F is widely prevalent in China, while genotype G appears in localized areas and is exhibiting a trend of gradual expansion. To understand the genetic characteristics of genotype G strains in China, we selected two genotype G MuV strains that were isolated from Dalian, Liaoning for analysis. [Methods] The whole genomes of the two strains were sequenced, and the genotypes were determined according to the WHO reference strains. Furthermore, we compared the molecular characteristics among different genotypes and within genotype G. By comparison with the sequences of genotype G strains in other areas of China, we analyzed the features of genotype G MuVs in China, as well as the genetic distance and variations of key antigenic sites between the wild-type genotype G strains and the existing vaccine strains. [Results] The strains isolated in this study both belonged to genotype G, and they showed the nucleotide differences ranging from 4.2% to 6.9% from other 12 genotypes, with the greatest divergence from genotype A. Among the protein coding genes, the SH coding gene exhibited the largest variation, while the NP, M, and L coding genes were conserved. The P, F and HN coding genes demonstrated significant differences among different genotypes. The genotype G strains isolated in this study were closely related to the strain isolated in Jiangsu Province (Jiangsu.CHN/22.13/2), while they were distinct from the strains previously isolated in Liaoning Province. The genotype G strains isolated in this study lacked a N-glycosylation site (aa 12-14) but gained a N-glycosylation site (aa 464-466) in the key epitope of HN protein. In addition, the genotype G strains showed considerable differences in terms of neutralizing epitopes from the genotype A vaccine strain. These differences suggested that the mutations of these sites may potentially reduce the cross-protection effects of vaccine strains against wild-type MuV strains. Although there were some mutations in F protein, the functional region was conserved. [Conclusion] This study details the genotypic characteristics of genotype G MuVs in Dalian, highlighting their high similarities to the genotype G strains in China and the WHO reference strains, while underscoring significant differences from the genotype A vaccine strain used worldwide. These findings suggest the necessity of continuous surveillance of MuV strains in China and further studies of their epidemiology and virology, which could provide references for tracing MuVs, cutting the transmission route, and developing immunization strategies in China.

[Objective] To study the effect of Alistipesfinegoldii (AF) on inflammatory bowel disease (IBD) and the underlying mechanism. [Methods] Six-week-old male C57BL/6J mice were administrated with streptomycin for three days and then randomly assigned into the control, phosphate buffered saline (PBS), and AF groups. Mice were administrated with AF suspension (1×10⁹ CFU, 200 μL per mouse) or PBS by gavage for two weeks, followed by drinking of the water containing 2.5% dextran sulfate sodium (DSS) for one week for the modeling of colitis. The weight loss fraction percentage, fecal characteristics, blood fecesstools, and colon length were determined. The colon tissue was stained with hematoxylin-eosin for the scoring of histopathological changes, and feces samples were collected at the beginning and end of the experiment for sequencing of 16S rRNA gene amplicons at the beginning and end of the experiment. The mRNA levels of colon tissue-associated intestinal barrier proteins and inflammatory mediators were determined by qPCR. [Results] The mice in the AF group had severer disease conditions than those in the PBS group regarding the weight loss percentage, disease activity index, colon shortening, and histopathological score. Compared with the PBS group, the AF group showed down-regulated mRNA levels of occludin and claudin 5 and up-regulated mRNA level of interleukin (IL)-17A. The AF group had lower alpha diversity of intestinal flora than the PBS group, and the beta diversity showed significant differences between AF and PBS groups. The linear discriminant analysis effect size (LEfSe) results revealed that the significantly differential bacteria between AF and PBS groups were Bacilli, Erysipelotrichales, Erysipelotichaceae, Odoribacter, Marinifilaceae, Dubosiella, and Dubosiellanewyorkensis. [Conclusion] AF promotes the secretion of inflammatory mediators, impairs the permeability of the intestinal mucosa, and alters the structure and diversity of the intestinal flora, thereby promoting the development of IBD.

CsgD, a core regulatory protein for the biofilm formation of Salmonella, exerts its function by regulating the expression of key components (curli and cellulose) of the biofilm. In recent years, significant progress has been achieved in analyzing the regulatory network of Salmonella CsgD protein and its complex influencing factors. Focusing on the regulatory function of CsgD in the biofilm formation of Salmonella, this paper systematically introduces how environmental factors affect the CsgD expression and comprehensively analyzes the multi-level regulatory effects of various regulatory factors on CsgD, aiming to enrich our understanding about the mechanism and regulatory network of the biofilm formation of Salmonella and provide possible research directions.