Porcine deltacoronavirus (PDCoV), a major porcine intestinal coronavirus, has caused enormous economic losses to the pig industry. Up to now, there is no commercial vaccine available. [Objective] To obtain the epidemic strain of PDCoV and study its biological characteristics and pathogenicity, thereby providing biological materials for the development of an effective vaccine against PDCoV as soon as possible. [Methods] LLC-PK1 cells were used to isolate the virus from PDCoV-positive samples from a pig farm in Gansu Province. The virus was identified by observation of cytopathic effect (CPE), indirect immunofluorescence assay (IFA), and whole genome sequencing. [Results] After blind passage of the PDCoV-positive LLC-PK1 cells to P6, the cells became larger and rounded, and then shrunk and shed into single or clustered dense particles, typical features of CPE. The IFA results confirmed successful isolation of the PDCoV strain CHN/GSYD/2023. The whole genome sequencing and phylogenetic analysis showed that CHN/GSYD/2023 isolated in this study was more closely related to the strain from China and was located on a different clade from the strain CHN/XJYN/2016 preserved in our laboratory. After 5-day-old piglets were infected with CHN/GSYD/2023, 100% (5/5) of piglets became diseased. Autopsy and histopathology of piglets showed thinning small intestinal wall, a large amount of effusion in the intestinal cavity, ileum intestinal villus necrosis and other pathological damage. [Conclusion] A PDCoV strain CHN/GSYD/2023 was successfully isolated from PDCoV-positive samples in a pig farm in Gansu. The strain can be stably proliferated and passaged in LLC-PK1 cells, and it is highly pathogenic to suckling piglets.

[Objective] To investigate the genomic phylogeny as well as the in vivo and in vitro infection and replication characteristics of the tick-borne parainfluenza virus type 5 (strain PIV5-JC12) recently isolated from Yunnan Province. [Methods] The strain PIV5-JC12 was identified through cytopathic effect (CPE) observation, negative staining electron microscopy, and an indirect immunofluorescence assay (IFA) based on the P protein. We determined its optimal culture temperature by comparing viral proliferation efficiency at 33 ℃ and 37 ℃ in Vero cells. A phylogenetic tree based on the whole genome was constructed via the maximum likelihood method to elucidate the molecular evolutionary characteristics of this strain. After infection of six representative cell lines of different origins (Vero, MDCK, HeLa, Huh7.5, MRC-5, and BHK-21), CPE observation, RT-qPCR, and tissue culture infectious dose 50% (TCID₅₀) assays were employed to evaluate the virus replication kinetics. The in vivo pathogenicity of PIV5-JC12 was evaluated in Kunming (KM) and C57BL/6J mice. Mice were infected intranasally with high and low doses (2×10⁷ TCID₅₀ and 2×10⁶ TCID₅₀) and monitored for body weight and survival rate. The viral loads in various tissue and organ samples were measured at the time points of 1, 4, 7, and 10 days post-infection (dpi), and histopathological changes were examined. [Results] PIV5-JC12 induced CPEs, as manifested by the rounding and detachment of Vero cells. Irregular spherical particles with diameters of 50-200 nm were observed, and the specific P protein was identified by immunofluorescence. The tick-borne strain PIV5-JC12 showed the highest sequence identity with the tiger-borne strain PIV5 (OQ236149.1). Viral replication and proliferation in Vero cells were more efficient at 37 ℃ than at 33 ℃. PIV5-JC12 infected all the six cell lines of human, murine, simian, and canine origins. However, the CPEs varied among the cell lines, being more pronounced in Vero, MDCK and BHK-21 cells. Higher RNA replication efficiency was observed in Vero, MDCK, and HeLa cells. In vivo infection studies revealed differential susceptibility of KM and C57BL/6J mice to PIV5-JC12. The body weight loss (5%) was only observed in the high-dose infected C57BL/6J mice at 10 dpi. Lung viral loads in both mouse lines reached 10⁴-10⁵ copies/g, while no infectious virus was detected in the lung tissue at any of the time points examined. Histopathological staining analysis of lung tissue at the early stage (4 dpi) and late stage (10 dpi) of infection showed no significant pathological damage. [Conclusion] PIV5-JC12 isolated from tick samples from Yunnan Province shows broad cellular tropism and low pathogenicity in mice. The findings provide a basis for research on the pathogenic characteristics of PIV5 and its potential application as a vaccine vector.

Eumelanin, a natural biological pigment formed by the polymerization of 5,6-dihydroxyindole and its carboxylic acid derivatives, is ubiquitous in animals and microorganisms. Its highly conjugated molecular structure confers multiple functional properties, including broad-spectrum light absorption, antioxidant activity, free radical scavenging, and metal ion chelation, making it a promising material for applications in biomedicine, functional coatings, and environmental remediation. The conventional production of eumelanin relies largely on extraction from animal tissue or chemical synthesis, which are constrained by limited raw materials and uncontrollable product structures. Recently, microbial cell factory-based biosynthesis of eumelanin has attracted increasing attention due to its environmental sustainability and structural controllability. This review comprehensively summarizes the biosynthetic pathways, strategies for metabolic engineering and genetic engineering, analysis and characterization methods for eumelanin, and discusses future perspectives for the application and development of microbial eumelanin production.

Aeromonas veronii is a Gram-negative pathogenic bacterium that causes various diseases in aquatic animals and humans, posing a serious threat to aquaculture and public health. The type Ⅵ secretion system (T6SS) is a key virulence factor determining the pathogenicity of A. veronii. It is known that the bacterial enhancer-binding protein (bEBP) VasH is responsible for regulating the T6SS function, while whether this regulatory relationship exists in A. veronii remains unknown. [Objective] To elucidate the impacts of VasH on T6SS expression and function in A. veronii, thereby providing a theoretical basis for deciphering the mechanism of T6SS-mediated pathogenicity of A. veronii and for the subsequent prevention and control of A. veronii infections. [Methods] With A. veronii C4 as the wild-type strain, the VasH-deficient mutant strain ΔvasH and the complemented strain ΔvasH/p-vasH were constructed via a homologous recombination strategy. RT-qPCR was employed to measure the relative expression levels of T6SS genes in each strain to clarify the effect of VasH on T6SS gene expression. Growth curve establishment, transmission electron microscopy (TEM) for observing bacterial morphology, and the crystal violet assay for biofilm quantification were performed to determine the influences of VasH on pathogenic characteristics. An in vitro bacterial competition assay and a zebrafish model for determining the median lethal dose (LD₅₀) were employed to assess the comprehensive effects of VasH on bacterial competitiveness and pathogenicity. [Results] The VasH-deficient mutant strain ΔvasH and the complemented strain ΔvasH/p-vasH were successfully constructed. The deletion of VasH resulted in a decrease (P<0.05) in the expression of genes encoding both T6SS structural and effector proteins, indicating that VasH was responsible for regulating T6SS gene expression. The deletion of vasH did not significantly affect the growth or surface morphology/structure of A. veronii. However, it led to a significant increase in the biofilm formation and a significant decrease in in vitro bacterial competitiveness. The zebrafish infection assay showed that the LD₅₀ of ΔvasH was 1.58×10¹¹, which was 2.15 times that (7.34×10¹⁰) of the wild type. Moreover, at an infection concentration of 5×10⁸ CFU/mL, the death rate of zebrafish decreased from 33.3% in the wild-type infection group to 0 following infection with ΔvasH, indicating that deletion of vasH attenuated the virulence of A. veronii. [Conclusion] In A. veronii, VasH positively regulates T6SS gene expression. It may not be involved in regulating the growth state or external morphology of the pathogen but significantly influences the biofilm formation and competitiveness of A. veronii, thereby modulating the overall virulence during infection of the zebrafish host. This study provides essential research tools and lays a preliminary foundation for further exploration of the molecular mechanisms by which VasH mediates pathogenicity through regulating T6SS activity and function in A. veronii.

Microbial fertilizers are an important component of green agricultural inputs, playing a key role in reducing chemical fertilizer use, improving arable land quality, and mitigating agricultural emissions. Using the registration certificate data of microbial fertilizers in China from 2000 to 2025, this paper systematically analyzes the structural characteristics and regional patterns of China’s microbial fertilizer industry and takes Guangdong Province as a case to examine the development bottlenecks of this industry in Guangdong. The study finds that China’s microbial fertilizer industry has gone through three stages: slow start, steady growth, and explosive expansion, forming a clustered pattern centered on Shandong, Hebei, Heilongjiang, and Henan provinces. However, three major structural contradictions are becoming increasingly prominent. Specifically, the products are highly concentrated in microbial inoculants, bioorganic fertilizers, and compound microbial fertilizers; microbial strain resources are highly homogenized; and enterprises are scattered, small, and weak. The number of registration certificates in Guangdong Province (334) accounts for only 2.83% of the national total (11 813) and is merely 13.82% of that of Shandong Province (2 416), which ranks first in China. Nearly 40% of enterprises are in a state of one certificate for one product, indicating a severe mismatch between the industrial scale and Guangdong’s status as a major agricultural province. In response to the above problems, this paper proposes recommendations from six aspects: elevating the policy position of microbial fertilizers, mining and protecting microbial strain resources, reforming registration management, optimizing the enterprise ecosystem, bridging the gap in technology transfer, and exploring the paths tailored for Guangdong, aiming to provide a reference for the high-quality development of the microbial fertilizer industry in China and especially Guangdong Province.

[Objective] To explore genes related to the regulation of yeast spore germination, we previously screened for mutants defective in maintaining the quiescent state of spores. [Methods] Using the temperature-sensitive yeast mutant J33 with defective spore quiescence maintenance as the research material, heterozygous diploid strains were constructed through tetrad dissection and haploid fusion, and genetic segregation analysis was performed to clarify the genetic regulatory pattern of mutant phenotypes. The yeast genomic library complementation screening was applied to identify candidate mutant genes, and gene cloning and sequence alignment were conducted to confirm the mutation site. Furthermore, recombinant plasmids carrying wild-type and mutant TIP20 were constructed for functional complementation assays, and site-directed mutagenesis was used to verify the correlation between TIP20 mutation and strain phenotypes. [Results] Functional complementation experiments demonstrated that introduction of the wild-type TIP20 restored the growth at 37 ℃ and the normal spore germination phenotype of J33, while the mutant TIP20 and empty vector had no such effect. Site-directed mutagenesis analysis further confirmed that this single-base mutation was T1219G, a direct cause of the TS phenotype and defective spore germination of J33. [Conclusion] TIP20 is involved in the regulation of yeast spore germination. TIP20 encodes a subunit of the tethering complex involved in endoplasmic reticulum-Golgi retrograde transport. However, TIP20 is likely a multifunctional protein, and its mammalian homologue RINT1 has been reported to regulate the cell cycle checkpoint. Thus, TIP20 may also be involved in regulating the quiescent state of yeast cells.

[Objective] To characterize the successional dynamics of bacterial and fungal communities during leaf litter decomposition and elucidate the associations between keystone taxa and substrate component losses, thereby advancing our understanding of microbial regulation during litter decomposition in forest ecosystems. [Methods] We established an indoor microcosm with the leaf litter from Alnus cremastogyne to track microbial community succession during the litter decomposition. High-throughput sequencing, chemical composition analysis, and bacterial-fungal cross-domain co-occurrence network analysis were integrated to characterize microbial community dynamics, identify keystone taxa, and test their associations with loss rates of major chemical components across four decomposition stages (initial, 45%, 75%, and 90% mass loss). [Results] At the phylum level, bacterial and fungal community composition showed only minor changes in relative abundance across stages, with Pseudomonadota (relative abundance of 50%- 80%) dominating bacterial communities and Ascomycota (>95%) dominating fungal communities. In contrast, pronounced stage-dependent succession was observed at the genus level. Decomposition stage accounted for substantial variations in bacterial (R²=0.573, P<0.001) and fungal (R²=0.377, P<0.001) community structures. With the progression of decomposition, cross-domain networks exhibited increased nodes and connectivity and shifted from loose to modular structures, with positive correlations consistently exceeding negative correlations. The number of keystone taxa increased over time and became progressively dominated by fungi. During the first three decomposition stages, the number of bacterial nodes accounted for approximately 75% of total nodes, whereas at the 90% decomposition stage, the number of fungal nodes increased markedly (from 103 to 320), resulting in comparable proportions of bacterial and fungal nodes. At the 45% decomposition stage, keystone bacterial taxa were primarily associated with losses of non-structural components and hemicellulose, whereas at the 75% and 90% decomposition stages, keystone fungal taxa were more closely associated with cellulose and lignin losses. Functional predictions further supported this stage-specific division of labor, indicating stronger potential of structural carbon degradation at the late stages of decomposition. [Conclusion] Bacteria and fungi jointly participate in A. cremastogyne leaf litter decomposition with temporally differentiated contributions. Bacteria play a more prominent role during early and middle stages, whereas fungi become increasingly important at late stages. These findings indicate coordinated shifts in microbial community structure and resource utilization rather than simple taxonomic replacement, contributing new insights into microbial regulation during litter decomposition.

Ulcerative colitis (UC) is a chronic non-specific intestinal inflammatory disease with complex pathogenesis. Recent studies have identified a pivotal role of the gut microbiota in the etiology of the disease. Beneficial bacteria, such as Lactobacillus and Bifidobacterium, have been shown to regulate the balance of the gut microbiota, repair the mucosal barrier, and alleviate inflammation. In contrast, excessive proliferation or secretion of toxins by harmful bacteria, such as Escherichia, can damage the integrity of the mucosa, induce inflammation, and accelerate the progression of UC. The active ingredients of traditional Chinese medicine, such as Scutellariae radix polysaccharides, pulchinenosides, and ginsenoside Rg1, may offer a promising avenue for the treatment of UC by modulating the structure of the gut microbiota and enhancing the barrier function and mucosal integrity. The present article reviews the latest research progress in the regulation mechanism of the gut microbiota in UC and the traditional Chinese medicine intervention, with a view to providing new strategies and theoretical support for clinical treatment.

The efficient conversion of lignocellulosic biomass is at the core of ensuring the economic feasibility of biorefineries, where the comprehensive utilization of xylose serves as a determinant of overall conversion efficiency. Pichia kudriavzevii has demonstrated significant potential in industrial bioprocessing owing to its tolerance to low pH, high temperatures, and environmental stressors. However, its innate deficiency in xylose assimilation severely restricts its application in biomass valorization. [Objective] To elucidate the molecular mechanisms underlying the silencing of xylose metabolism in P. kudriavzevii E1, thereby providing a theoretical basis for the bioconversion of lignocellulosic feedstocks. [Methods] The xylose assimilation capacity of P. kudriavzevii E1 was evaluated, and its genome was analyzed to identify the genes and metabolic bottlenecks associated with xylose assimilation. Comparative transcriptomics was employed to characterize the differential expression of metabolic genes before and after the introduction of a xylose transporter. Furthermore, the heterologous expression of genes involved in efficient xylose metabolism was performed to verify specific rate-limiting steps within the pathway. [Results] Bioinformatics analysis, coupled with the functional restoration of xylose uptake via heterologous transporter expression, confirmed that the lack of high-affinity xylose transporters was the primary limiting factor for xylose assimilation in P. kudriavzevii E1. Although three genes—PkXYL1, PkXYL2, and PkXKS1—encoding core enzymes of the xylose redox pathway were natively present in the P. kudriavzevii E1 genome, in vitro enzymatic assays revealed that the low relative activity of PkXR was a critical cause of substrate accumulation and slow xylose metabolism. Comparative transcriptomics of the engineered strain P. kudriavzevii E1-Xpg4562 indicated that yeast cells underwent profound metabolic reprogramming in xylose-containing media, preferentially activating ribosome biogenesis and oxidative phosphorylation. However, the significant downregulation of TAL1 and the insufficient transcriptional response of genes in the pentose phosphate pathway (PPP) resulted in inefficient PPP flux. This prevented the effective redirection of carbon flux into glycolysis, thereby obstructing downstream xylose metabolism. Finally, quantification of the expression of key xylose metabolism genes identified by transcriptomics further demonstrated that the uncoordinated transcriptional regulation of essential downstream genes hindered overall metabolic efficiency. [Conclusion] The silencing of xylose metabolism in P. kudriavzevii E1 results from the combined effects of deficient substrate transport, low endogenous catalytic activity, and uncoordinated transcriptional regulation. This study provides a crucial theoretical foundation for the precision engineering of xylose metabolic pathways in non-conventional industrial yeasts.

Early life is a critical window for the establishment of the infant gut microbiome and the shaping of its metabolic functions, and gestational age and feeding mode are considered key determinants of this process. [Objective] To compare the fecal gut microbiome and metabolome between preterm and full-term infants under breastfeeding and non-breastfeeding conditions, thus exploring the effects of feeding mode and gestational age on early-life gut microbial ecology and metabolic features. [Methods] Infants were assigned into four groups: breastfeeding preterm infants (BPI), non-breastfeeding preterm infants (NBPI), breastfeeding full-term infants (BTI), and non-breastfeeding full-term infants (NBTI), with 10 infants per group. The 16S rRNA gene sequencing and untargeted metabolomics analysis were performed. Alpha/beta diversity analyses, differential abundance testing, and linear discriminant analysis effect size (LEfSe) were performed to identify key microbial taxa. Partial least squares-discriminant analysis (PLS-DA), volcano plots, and KEGG pathway enrichment were employed to determine differential metabolites and functional pathways, followed by microbiome-metabolite association network analysis. [Results] The 16S rRNA gene sequencing showed that the gut microbiome in the BTI group was dominated by Actinomycetota, Bifidobacterium (45.98%), and Bifidobacterium breve, forming a typical “breastfeeding-type” structure. The BPI group showed enrichment of Pseudomonadota and Streptococcus, with attenuated dominance of Bifidobacterium. Among non-breastfed infants, the NBTI group was dominated by Enterococcus (59.20%), whereas the NBPI group showed a fluctuating gut microbiome. Untargeted metabolomics further revealed functional differences consistent with these compositional patterns. KEGG enrichment indicated that differential metabolites were mainly involved in amino acid metabolism, lipid metabolism, bile acid-related pathways, and carbohydrate digestion and absorption. At the level of key metabolites, the BPI group showed significant enrichment of metabolites related to antioxidant and immune support, such as glutathione and vitamin D sulfate conjugates; the BTI group enriched long-chain polyunsaturated fatty acids and indole-derived metabolites; and non-breastfeeding groups generally exhibited accumulation of fermentable carbohydrates and specific bile acid derivatives. Correlation analysis confirmed a strong positive association between Bifidobacterium and indole-related metabolite outputs in breastfeeding groups, whereas microbiome–metabolite networks were looser in non-breastfeeding groups. [Conclusion] Both gestational age and feeding mode are related to differences in the early gut microbiome structure and related metabolic characteristics of infants, with the association between feeding mode and metabolic profile differences being more prominent. Gestational age may affect the establishment pattern of dominant microbial taxa in the context of breastfeeding. As a pioneering exploratory study, this study preliminarily reveals the specificity of gut microbiome structure and functional metabolism in different populations of infants, providing a basis for subsequent prospective cohort validation, mechanism research, and early nutritional intervention optimization.