Porcine deltacoronavirus (PDCoV), an emerging virus globally prevalent, causes watery diarrhea, vomiting, and dehydration of newborn piglets, posing severe economic losses in the swine industry. Moreover, with the characteristic of cross-species transmission, PDCoV can infect human and farmed animals, posing a serious threat to human health. Pyroptosis is a form of programmed cell death mediated by members of the Gasdermin family, which plays a role in defending and eliminating viruses. Coronaviruses, however, have developed precise strategies to antagonize pyroptosis and evade immune responses. This review expounds the biological characteristics of PDCoV, the process of pyroptosis, and the antagonism of Gasdermin D-mediated pyroptosis by PDCoV, aiming to enrich the knowledge about the antagonism of immune responses by PDCoV and lay a theoretical foundation for the prevention and control of this virus.

[Objective] To evaluate the safety and immunogenicity of outer membrane vesicles (OMVs) of Fusobacterium nucleatum prepared under the pH conditions simulating normal intestinal and tumor microenvironments, and to lay a foundation for the later development of OMV-based vaccines against F. nucleatum. [Methods] Ultra-high-speed centrifugation and density gradient centrifugation were employed to isolate the OMVs of F. nucleatum under different pH conditions. Three models of human colorectal cancer cells (HCT116), human colonic epithelial cells (HCoEpiC), and mouse macrophage Raw264.7 were infected by F. nucleatum. The cell proliferation was assessed by 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT) assay and cell counting kit-8 (CCK-8) assay, and the cell apoptosis were evaluated by flow cytometry and in situ fluorescence of adherent cells. The safety in vivo was detected by blood routine and whole blood index of mice. The enzyme-linked immunosorbent assay (ELISA) was employed to examine the cell immunogenicity, and the adhesion inhibition assay was conducted to assess cell immunoprotection. [Results] Acidic outer membrane vesicles (aOMVs) and neutral outer membrane vesicles (nOMVs) had no significant different effects on the proliferation or apoptosis of HCoEpiC, HCT116, and Raw264.7 cells. Both nOMVs and aOMVs at a concentration of 25 μg/mL did not lead to significant hemolysis of red blood cells, and the routine blood and whole blood test results of the mice treated with aOMVs were within the normal ranges. The results demonstrated that both aOMVs and nOMVs exhibited good immunogenicity and reduced the adhesion of F. nucleatum to colon cancer cells DLD-1. The aOMVs outperformed nOMVs regarding immunogenicity. [Conclusion] Both aOMVs and nOMVs had good safety and immunogenicity, and aOMVs were superior to nOMVs.

[Objective] In view of the enhanced cell-to-cell spread ability of the dsbA-deleted strain (ΔdsbA) of Listeria monocytogenes, this study aims to elucidate the mechanism that how the disulfide bond formation protein DsbA mediates this biological process. [Methods] The mRNA and protein levels of virulence factors in the wild type and ΔdsbA were compared by RT-qPCR and Western blotting, respectively. The immunofluorescence co-localization analysis method was employed to observe the impact of DsbA deficiency on the actin recruitment by the virulence factor ActA in the cell-to-cell spread of L. monocytogenes (analyzing the length and quantity of the comet tails formed on one side of the bacteria by co-localization of ActA and actin). The presence or absence of interaction between DsbA and ActA was determined by isothermal titration calorimetry (ITC). [Results] Compared with the wild type, ΔdsbA showed no significant changes in the mRNA levels of virulence factors, downregulated protein levels of InlA, InlB, PlcA, and PlcB, and upregulated protein levels of ActA and LLO. In addition, ΔdsbA showed increased number and average length of comet tails, which indicated that the actin recruitment of ΔdsbA was enhanced. The ITC results revealed that DsbA bound to ActA, which gradually showed endothermic reactions, suggesting the presence of interaction between DsbA and ActA. [Conclusion] This study proved for that DsbA attenuated the recruitment ability of actin by regulating virulence proteins, thus affecting the cell-to-cell spread of L. monocytogenes. The findings help to further dissect the virulence regulatory mechanisms of L. monocytogenes during host infection, which is of great importance for controlling the contamination of zoonotic intracellular pathogens threatening public health.

[Objective] To investigate the changes of microbial communities on loess slopes with different noise conditions under the influences of temperature and time. [Methods] Based on the changes in soil phosphate content, the noise was determined at 70, 90, and 110 dB. The microbial communities presented variations along the temperature gradients of −5, 15, and 35 ℃ and the noise duration of 2, 4, and 6 h. Subsequently, metagenomic sequencing was carried out for the soil microbial communities. [Results] At the phylum level, Actinobacteria, Mucoromycota, Thermoproteota, and Myxococcota showed differences in the relative abundance among groups (P < 0.05). At the genus level, Arthrobacter, Rhizophagus, Pseudarthrobacter, Actinomadura, Kocuria, Rubrobacter, and Corynebacterium demonstrated different relative abundance among groups (P < 0.05). At the species level, there were significant differences in the relative abundance of Rhizophagus irregularis, Actinomadura sp. WMMB 499, Rubrobacter tropicus, Arthrobacter sp. PGP41, Arthrobacter sp. 24S4 2, and Arthrobacter crystallopoietes among groups (P < 0.05). [Conclusion] Different noise environments have significant effects on the relative abundance of soil microorganisms at the phylum, genus, and species levels.

Escalating resistance of pathogens, especially Gram-negative bacteria, to antibiotics has become a public health problem arousing worldwide concern because of the abuse of antibiotics. The "Trojan Horse" strategy emerges as a promising approach to the development of new antibacterial agents. This strategy improves the antibacterial activity or broadens the antibacterial spectrum of antibiotics by using the siderophore-mediated bacterial iron transport system. In 2019, cefiderocol as the first siderophore-antibiotic conjugate was approved for marketing, which has garnered wide attention of scientists in this field. Currently, researchers mainly focus on siderophores or utilizing antibiotics with different mechanisms and ignoring linkers in the design of agents based on the "Trojan Horse" strategy. This review will summarize the impact of different linkers of conjugates on antibacterial activity, which could provide reference for the development of new antibacterial drugs and combating bacterial resistance.

[Objective] To obtain a stable microbial consortium with a high yield of caproate and achieve high-value carbon recovery from Baijiu-making wastewater (Huangshui). [Methods] We used the plate screening approach to obtain a simplified caproate-producing microbial consortium, evaluated the preferred carbon source of the consortium, and optimized the substrate concentration, pH, and feeding strategy. The metagenomics based on nanopore sequencing was employed to determine the composition and stability characteristics of the simplified caproate-producing microbial consortium. [Results] SimpCom1, a simplified caproate-producing microbial consortium, demonstrated significantly higher conversion rate of lactate than glucose to caproate. When SimpCom1 was used to ferment unsterilized Huangshui, we controlled the working concentration of Huangshui between 30% and 50% and initial pH 5.50 to achieve stable growth and metabolism of the consortium for caproate production. The fermentation was carried out in a fed-batch manner with 50% Huangshui, initial pH 5.50, and pH 6.50–7.00 after 48 h. Within four fed-batch fermentation cycles, the average caproate titer, productivity, proportion of caproate in total acids, and conversion rate of lactate to caproate reached 16.83 g/L, 3.05 g/(L·d), 67.27%, and 0.42 g/g, respectively. The metagenomic analysis showed that Caproicibacterium lactatifermentans, Ligilactobacillus acidipiscis, Clostridium tyrobutyricum, and 'Butyriproducens baijiuensis BJN0003' were the core species of SimpCom1. C. lactatifermentans and 'B. baijiuensis BJN0003' remained stable growth and metabolism in the unsterilized Huangshui, with the relative abundance of 45.3% and 6.7%, respectively, at the end of fermentation with 50%-diluted Huangshui. [Conclusion] We successfully established an efficient and low-cost approach for producing caproate by fermentation of unsterilized Baijiu-making wastewater with a simplified microbial consortium containing C. lactatifermentans and 'B. baijiuensis BJN0003'.

In Pseudomonas aeruginosa, tryptophan can be converted into anthranilate via the KynABU pathway, and anthranilate as a substrate is further converted into alkyl quinolones (AQs), including 2-heptyl-3-hydroxy-4-quinolone (PQS) and 2-heptyl-4-quinolone (HHQ), under the action of pqsABCDE, a synthetic gene cluster of AQs. At the same time, anthranilate can be degraded into the tricarboxylic acid cycle under the catalysis of the anthranilate dioxygenase complex AntABC, while the biological effect of AntABC on P. aeruginosa remains unclear. [Objective] To construct and characterize the phenotype of the antABC-deleted mutant of P. aeruginosa. [Methods] With P. aeruginosa PAO1 as the starting strain, we constructed the antABC-deleted mutant by homologous recombination to study the effects of the operon on tryptophan degradation, biofilm formation, pyocyanin synthesis, motility, and virulence of P. aeruginosa. [Results] The deletion of antABC or kynU completely inhibited the growth of P. aeruginosa with tryptophan as the sole carbon source, while ΔpqsA did not present this phenotype, indicating that antABC was essential for the degradation of tryptophan by P. aeruginosa, and KynABU-AntABC pathway was the only way for the degradation of tryptophan by the bacterium under the culture conditions in this study. In addition to affecting tryptophan degradation in P. aeruginosa, the deletion of antABC promoted the biofilm formation of P. aeruginosa by inducing the expression of the extracellular polysaccharide synthesis operon pel, and it promoted the synthesis of pyocyanin by inducing the expression of the pyocyanin synthesis operons phz1 and phz2. In addition, the deletion of antABC enhanced the swarming motility and twitching motility of P. aeruginosa. Interestingly, further deletion of pqsA completely reversed the physiological phenotypes of ΔantABC. Therefore, the regulation of antABC on these physiological phenotypes depended on AQs. The deletion of antABC increased the HHQ accumulation while inhibiting the synthesis of PQS in P. aeruginosa. These results indicated that the regulation of these physiological phenotypes by antABC mainly depended on HHQ. In addition, the deletion of antABC enhanced the virulence of P. aeruginosa to Chinese cabbage and Galleria mellonella larvae, while further deletion of pqsA only partially reversed this virulence phenotype. Moreover, the deletion of antABC caused increased accumulation of anthranilate in P. aeruginosa. Therefore, the enhancement of antABC deletion on the virulence of P. aeruginosa was mediated by HHQ and anthranilate together. Finally, bioinformatics analysis revealed that the missense mutations of antABC operon occurred in more than 90% of clinical isolates of P. aeruginosa. Therefore, antABC was expected to be used as a biomarker to determine whether clinical isolates of P. aeruginosa were highly virulent. [Conclusion] AntABC plays an important role in the tryptophan degradation, biofilm formation, pyocyanin synthesis, motility, and virulence of P. aeruginosa. This finding lays a foundation for the clinical diagnosis and antimicrobial development of P. aeruginosa infection.

[Objective] To study the sulfur oxidation characteristics of Halothiobacillus diazotrophicus LS2 under different oxygen levels and to decipher the mechanism of strain LS2 adapting to low-oxygen environments. [Methods] The concentrations of S₂O₃^2- and SO₄^2- were measured by ion chromatography. Bacterial growth was determined by plate dilution coating method. The differentially expressed genes and related metabolic pathways were identified and analyzed by transcriptome sequencing and bioinformatics technology. [Results] Strain LS2 oxidized reduced sulfur compounds and grew under 0.2%–21.0% oxygen, and it maintained high sulfur oxidation activity under the oxygen level above 1.6%. Comparative transcriptomic analysis screened out 851 differentially expressed genes that might be related to the adaptation to low oxygen, including 464 up-regulated genes and 387 down-regulated genes. In sulfur metabolism, thiosulfate sulfurtransferase, sulfur oxidase/reductase, and sulfide: quinone oxidoreductase were up-regulated, while the Sox enzyme system was down-regulated, which indicated that strain LS2 might change the sulfur oxidation pathway to adapt to low-oxygen environment. In the low-oxygen group, the cbb₃-type cytochrome c oxidase was up-regulated to increase the O₂-binding efficiency. Meanwhile, since less electron could be received by O₂, the nitrogenase genes nifDKH and Fix complex genes fixA, fixB, fixC, fixX were up-regulated, making N₂ and CO₂ the alternative electron accepters to maintain redox balance, which explained the higher maximum bacterial growth in low-oxygen environments. [Conclusion] Strain LS2 is a sulfur-oxidizing bacterium that can maintain high sulfur oxidation activity in the low-oxygen environment. Sulfide: quinone oxidoreductase, high-oxygen-affinity terminal oxidases, and nitrogenase play a role in the adaptation to the low-oxygen environment. This study is of positive significance for deciphering the mechanism of sulfur oxidation under low oxygen and provides a theoretical basis for optimizing the treatment process of sulfur-containing wastewater.

[Objective] The Yellow River estuary located at the confluence of the Yellow River, land, and ocean is an area with mixed freshwater and seawater and a diverse and productive estuary ecosystem. This study aims to characterize the bacterial communities in freshwater and seawater of the Yellow River estuary. [Methods] High-throughput absolute abundance quantification was adopted to measure the absolute abundance of bacterial communities. The dominant taxa, α and β diversity, co-occurrence network, assembly mechanisms, and potential functions were compared between the bacterial communities in freshwater and seawater. The correlations between dominant taxa and environmental factors were explored. [Results] The absolute abundance of bacteria in freshwater was 2.61×10⁶ copies/mL, which was 1.8 times of that in seawater. The common dominant phyla in freshwater and seawater were Actinomycetota, Pseudomonadota, Cyanobacteriota, and Bacteroidota, with significant differences in absolute abundance. The abundance of Actinomycetota ranked first in freshwater, which was approximately equal to the sum of all dominant phyla in seawater. The abundance of Pseudomonadota was the highest in seawater. The alpha diversity of bacteria in freshwater was higher than that in seawater. There were significant differences in the bacterial community structure between freshwater and seawater, mainly due to the differences in the abundance of the dominant taxa. The bacterial co-occurrence network in freshwater was more complex and stable than that in seawater, and stochastic processes dominated the bacterial community assembly in both freshwater and seawater. The bacterial communities in freshwater and seawater presented different functions, while they shared some common functions. Metabolism was the most abundant function, with higher relative abundance in freshwater than in seawater. Five environmental factors ((pH, oxidation-reduction potential (ORP), electrical conductivity (EC), total organic carbon (TOC), and total nitrogen (TN)) correlated with the dominant bacterial taxa to different extent. There were collinear relationships among the four environmental factors except EC. The dominant genera showing positive correlations with pH, TOC and TN were all negatively correlated with ORP, and vice versa. Actinomycetota and Pseudomonadota were positively and negatively correlated with pH, respectively. [Conclusion] The bacterial communities showed great differences between freshwater and seawater in the Yellow River estuary. The differences were mainly reflected in the abundance, diversity, functional structure, and co-occurrence network. The bacterial communities in freshwater and seawater had similar dominant taxa and assembly mechanisms. The results provide data support for studying the microbial ecology and exploiting microbial resources in the Yellow River estuary.

Airborne microorganisms (AMs), including bacteria, fungi, and viruses, are ubiquitous. They are indispensable components of the atmospheric ecosystem, play an essential role in maintaining the stability and functions of the atmospheric ecosystem. AMs include not only beneficial microorganisms but also pathogenic microorganisms, which pose a threat to human health. Therefore, comprehensively revealing the distribution characteristics and succession patterns of AMs is of great significance for improving air quality, safeguarding human health, and ensuring national biosafety. This review systematically elucidates the sources, distribution characteristics, influencing factors, and categories of pathogenic microorganisms as well as the health risks associated with AMs. It contributes to the in-depth understanding of AMs pollution and its health risks, providing a scientific basis for preventing and controlling the pollution and protecting human health and eco-environment.