[Objective] Porcine deltacoronavirus (PDCoV) is a major porcine enteric coronavirus, causing huge economic losses to the pig breeding industry worldwide. However, there is no commercial vaccine available for this virus. The spike (S) protein is a key factor inducing host immune response. In this study, the two sites 855 and 856 in the loop between the heptapeptide repeat-1 (HR1) and the central helix of PDCoV S protein were mutated to proline (E855P and V856P). Then, the recombinant S protein and mutated S protein (S2P) were expressed and purified by the ExpiCHO-S eukaryotic expression system, and their immunogenicity and immunoprotecive performance were evaluated for developing a PDCoV subunit vaccine with good immune effect. [Methods] The serum level of the specific antibody IgG in immunized mice was measured by indirect enzyme-linked immunosorbent assay. The serum neutralization test was carried out to determine the titer of neutralizing antibodies in the immunized mice. The proliferation of T lymphocytes in immunized mice was detected by flow cytometry. The secretion levels of interferon (IFN)-γ, IFN-α, interleukin (IL)-2, and IL-4 were determined. RT-qPCR was employed to measure the PDCoV load in the intestinal tissue of mice after challenge. Tissue sections were prepared to observe the intestinal lesions of mice. The distribution of PDCoV antigen in the intestinal tissue of mice was detected by immunohistochemistry. [Results] High levels of anti-PDCoV specific IgG antibodies were produced in mice after intramuscular injection of S and S2P subunit vaccines, and the serum of mice 42 days after immunization had a neutralizing effect on PDCoV. The 50% neutralizing protective titer of LLC-PK cells in the S2P group was significantly higher than that in the S group. In addition, the immunization with S and S2P significantly induced the proliferation of CD₄⁺ T lymphocytes in mice, which was higher in the S2P group than in the S group. The immunization with S2P induced the proliferation of CD₈⁺ T lymphocytes in mice, and the level of CD₈⁺ T lymphocytes showed no difference between the S group and the PBS group. The levels of IFN-γ, IFN-α, IL-2, and IL-4 in the S and S2P groups were significantly higher than those in the PBS group and had no difference between the S and S2P groups. The challenge assay results showed that the PBS group presented PDCoV, pathological damage, and a large number of PDCoV antigens in the intestinal tissue, while neither PDCoV nor intestinal tissue damage was detected in the S and S2P groups, which showed no significant difference between the two groups. [Conclusion] S2P induces higher level of the humoral immune response against PDCoV in mice than S. The vaccines prepared with both S2P and S have protective effects on mice. The findings lays a foundation for the follow-up study of PDCoV subunit vaccines.

[Objective] There are numerous non-rhizobia in addition to rhizobia in the root nodules of leguminous plants. Despite the extensive studies about the endophytic bacteria in other plant tissues, little attention has been paid to the species diversity of non-rhizobia in root nodules. Therefore, further research is needed to explore the significance and ecological roles of non-rhizobia. [Methods] The root nodules of wild Sophora davidii (Franch.) Skeels, a leguminous nitrogen-fixing shrub growing in the hilly-gully loess region of northern Shaanxi, were collected. The species diversity of rhizobia and non-rhizobia in the root nodules of S. davidii was systematically studied by the conventional culture method. The plant growth-promoting effects of the strains were evaluated and their growth-promoting effects on wheat seedlings were verified. [Results] A total of 320 strains of endophytic bacteria were isolated from the root nodules of S. davidii in six counties/districts in northern Shaanxi. The phylogenetic analysis based on the 16S rRNA gene sequences identified the strains into 55 genera, 35 families, 17 orders, 17 classes of 4 phyla. Pseudomonas (18.44%), Bacillus (17.81%), and Mesorhizobium (11.56%) were the dominant genera. The results of re-inoculation experiments showed that Mesorhizobium sp. and Ochrobactrum sp. HL-2 formed root nodules with the host plant. Furthermore, the plant growth-promoting characteristics of 192 strains isolated Baota District were studied. The results showed that 115, 20, 78, and 18 strains possessed the abilities of fixing nitrogen, solubilizing phosphorus, producing indole-3-acetic acid (IAA), and secreting siderophores, respectively. Four elite strains were selected and inoculated alone or in combination into the wheat seedlings in pots, and their growth-promoting effects on the agronomic traits of wheat seedlings were evaluated. The results indicated that the treatment HIJ increased the plant height and fresh weight of wheat seedlings by 49.65% and 140.00% respectively. The treatments HK and IK increased the root length and chlorophyll content by 45.84% and 25.48%, respectively. [Conclusion] There are diverse non-rhizobia in the root nodules of S. davidii. The results of this study have great scientific significance for exploring the role of such microbial resources in natural ecosystems and enriching the resource pool of endophytic bacteria. Additionally, the results provide a theoretical basis for the application of these strains in ecological restoration in the arid region of northern Shaanxi.

[Objective] To explore the role of S1PP in the morphological differentiation, pathogenic process, and maintenance of sphingolipid balance of Magnaporthe oryzae. [Methods] We employed homologous recombination to delete the S1PP gene MoLCB3 from M. oryzae and characterized the obtained mutant ΔMolcb3 was by phenotypic analysis, gene complementation, and lipid metabolomics. Furthermore, we deleted the sphingosine kinase (SK) gene MoLcb4 from ΔMolcb3 to explore the relationship between MoLcb3 and MoLcb4. [Results] The deletion of MoLCB3 resulted in significant decreases in the mycelial growth rate and spore production and affected conidial malformation and initial appressorium formation. ΔMolcb3 completely lost the pathogenicity to barley. Moreover, the ΔMolcb3 mutant were significantly different from the wild type in responding to hyperosmic stress, cell wall integrity stress, high temperature stress, and fungal lipid synthesis inhibitors triadimefon and myriocin, suggesting that MoLcb3 was involved in these stress responses and lipid anabolism. Interestingly, the double mutant ΔMolcb3ΔMolcb4 basically compensated for all phenotypic defects of ΔMolcb3. In addition, lipid metabolomics showed that compared with the wild type, ΔMolcb3 presented significantly different levels of lipids, such as free fatty acids, ceramides, and phosphatidyl inositol. [Conclusion] MoLcb3 plays an important role in the mycelial growth, sporulation, spore germination, pathogenicity, stress responses, and lipid homeostasis. In addition, knockout of MoLCB4 can cushion the effects of MoLcb3 deletion. The results of this study provide new ideas for elucidating the sphingolipid metabolic pathway of M. oryzae and the development of inhibitors of fungal lipid biosynthesis.

[Objective] To explore the effects of compound lactic acid bacteria on the bacterial diversity and metabolites in the fermentation process of air-dried beef. [Methods] The lactic acid bacteria isolated in the early stage were inoculated into beef for fermentation with different strain combinations: C (Lactococcus garvieae TC-6:Pediococcus pentosaceus TMR-WJG, 1:1), D (L. garvieae TC-6:L. lactis TC-2, 1:1), G (P. pentosaceus TMR-WJG: L. lactis TC-2, 1:1), H (L. garvieae TC-6:P. pentosaceus TMR-WJG: L. lactis TC-2, 1:1:1), and K (without inoculation). High-throughput sequencing and non-targeted metabolomics were employed to study the bacterial community structure and metabolites, respectively, in air-dried beef inoculated with different combinations of lactic acid bacteria. [Results] A total of 304 species of bacteria belonging to 223 genera of 19 phyla were detected. Psychrobacter was predominant in the air-dried beef, with the average relative abundance of 52.21%. A total of 1 782 significantly differential metabolites were identified, including alkaloids, lipids, organic acids, and other metabolites related to flavor formation. The correlation analysis between microbiome and metabolome confirmed that the structures of bacterial communities differed significantly in the air-dried beef samples with different starters, which contributed to the differences of metabolites between groups, especially between groups C and K (P < 0.05). Specifically, the inoculation lowered the levels of coumarin and corilagin and elevated the levels of camellianin A, octadecadienoate, and lippioside Ⅱ. [Conclusion] The compound lactic acid bacteria selected in this study had a significant effect on the microbial community structure in air-dried beef. The quality formation of air-dried beef may be related to the microbial community structure and microbial metabolites. The compound lactic acid bacteria selected in this study demonstrated a potential application value.

The spread of antibiotic resistance has aroused global concern. The development of technologies for detecting antibiotic resistance genes (ARGs) is essential for curbing the migration and spread of ARGs from the environment to plants/animals and human populations. This paper describes the development timeline of existing nucleic acid detection technologies and their first applications to the detection of ARGs and summarizes their detection principles, advantages and disadvantages, and development potential. Furthermore, this paper prospects that isothermal amplification combined with CRISPR/Cas might be the core technology for the development of in-situ rapid detection methods. By reviewing the development history of each technology, this paper aims to give insights into the development and applications of technologies for detecting ARGs and provide technical support for the research and control of antibiotic resistance transmission.

[Objective] To investigate the acclimation mechanisms of straw-decomposing microbiomes in response to historically different climate conditions as characterized by extreme temperature distinction, we collected two native forest soil samples from the tropical (annual mean temperature: 25 ℃) and cold-temperate (annual mean temperature: −2 ℃) zones at a distance of 3 860 km. [Methods] Microcosm incubation was conducted at a low temperature (10 ℃), a high temperature (35 ℃), and alternated high and low temperatures (10 ℃/35 ℃). The two native forest soil samples were inoculated for targeted cultivation of straw-decomposing microbiomes. After 12 consecutive weeks of passage, 16S rRNA gene sequencing was carried out to analyze the microbial community composition. [Results] At 10 ℃, higher straw decomposition rate was observed in the forest soil from Changbai Mountain in the cold-temperate zone (15.5%) than that from the tropical zone. At 35 ℃, the decomposition rate in the soil from Sanya in the tropical zone (33.1%) was higher than that from Changbai Mountain The results of linear discriminant analysis effect size (LEfSe) showed that the dominant straw-decomposing genera included Duganella, Pedobacter, Janthinobacterium, and Serratia after 12 weeks of enrichment at 10 ℃ with the forest soil from Changbai Mountain. The dominant genera were Paenibacillus and Rhodanobacter after enrichment at 35 ℃, and Stenotrophomonas, Burkholderia, and Achromobacter after enrichment at 10 ℃/35 ℃. As for the forest soil from the tropical zone, the enriched dominant genera were Pseudomonas, Acinetobacter, and Flavobacterium at 10 ℃, Cupriavidus at 35 ℃, and Enterobacter and Cohnella at 10 ℃/35 ℃. [Conclusion] This study revealed the indicator microbial species for straw decomposition at different temperatures in native forest soils from geographically highly distinct regions with a 3 860 km distance. The results suggest that temperature could have likely played a pivotal role in shaping the microbiomes for straw decomposition. The findings provide a scientific basis for mining the straw-decomposing microbial resources in the cold zone in northeast China and the tropical zone in south China.

[Objective] To mine the differentially expressed genes (DEGs) of Kocuria rhizophila DC2201 exposed to clindamycin hydrochloride at 0.5 minimum inhibitory concentration (MIC) and reveal the response mechanism of Kocuria rhizophila DC2201 to clindamycin hydrochloride. [Methods] With the Kocuria rhizophila DC2201 cells cultured in LB liquid medium as the control, Illumina HiSeq platform was used for paired-end sequencing to determine the gene expression of Kocuria rhizophila DC2201 cells exposed to clindamycin hydrochloride at 0.5 MIC. Real-time fluorescence quantitative PCR was then conducted for validation. [Results] A total of 1 202 significantly DEGs were screened out from Kocuria rhizophila DC2201 under the stress of clindamycin hydrochloride, including 604 significantly up-regulated genes and 598 significantly down-regulated genes. After gene ontology (GO) annotation, 1 041 significantly DEGs were annotated into 35 GO terms of molecular function (MF), cell composition (CC), and biological process (BP). The Kyoto encyclopedia of genes and genomes (KEGG) enrichment analysis predicted 16 significantly DEGs related to DNA repair, 43 significantly DEGs related to ribosomal synthesis, 28 DEGs associated with ATP-binding cassette (ABC) transporters, 77 significantly DEGs associated with the pentose phosphate pathway, glycolysis, tricarboxylic acid (TCA) cycle, starch and sucrose, pyruvate, butyrate and other carbohydrate metabolisms, and 5 significantly DEGs related to peptidoglycan synthesis. [Conclusion] Kocuria rhizophila DC2201 exposed to clindamycin hydrochloride adopts a global response mechanism. It increases the efflux of clindamycin hydrochloride by up-regulating the gene expression of major facilitator superfamily (MFS) transporters in the multidrug resistance (MDR) family. By enhancing DNA repair and RNA metabolism pathways, the strain ensures the genomic stability and normal RNA function. In addition, it enhances the ribosome synthesis pathway to compensate for the protein synthesis barrier caused by the binding of clindamycin hydrochloride with the 50S ribosome. Furthermore, the strain reduces the absorption and transportation of carbohydrates to restrain the energy metabolisms pathways, thus slowing down the growth and reducing the energy demand. Correspondingly, the cell wall stability of Kocuria rhizophila DC2201 is also affected.

[Objective] To explore the effects of cell walls of Saccharomyces cerevisiae on the intestinal microbiota in finishing bulls by 16S rDNA and ITS sequencing. [Methods] A total of 40 simmental crossbred finishing bulls weighing about 550 kg were randomized into 4 groups, with 10 bulls in each group. The control group was fed with a basic diet, and 5, 10, and 15 g cell walls of S. cerevisiae were added to the diet of each bull per day in trial 1, 2, and 3 groups, respectively. The preliminary trial and trial lasted for 10 days and 94 days, respectively. Intestinal feces were collected 7 days before the end of the trial. [Results] 16S rDNA: (1) The Chao and ACE indices in the trial 3 group were higher than those in other groups (P < 0.05); (2) Firmicutes and Bacteroidota were the dominant phyla, and Prevotella_9, Faecalibacterium, Succinivibrio, Bacteroides, and Bifidobacterium were the dominant genera; (3) The linear discriminant analysis effect size (LEfSe) revealed one differential species (LDA≥4.0, P < 0.05) playing an important role in the trial 2 group. ITS: (1) There was no significant difference in the alpha or beta diversity among groups (P > 0.05); (2) Ascomycota with the relative abundance above 50.00% was the dominant phylum. Penicillium, unidentified_Ascomycota_sp., Aspergillus, Orpinomyces, and Eurotium were the dominant genera; (3) LEfSe revealed 8 differential species (LDA≥3.0, P < 0.05), which included 3, 3, and 2 differential species playing an important role in the control, trial 2, and trial 3 groups, respectively. [Conclusion] Under conditions of this study, adding 10–15 g/d cell walls of S. cerevisiae in the basic diet increased the richness of intestinal microbiota and the relative abundance of beneficial bacteria Provetella_9, Tolypocladium, and Torulaspora, which were conducive to improve intestinal microecological environment of finishing bulls.

Potato scab caused by Streptomyces scabies has become a bottleneck threatening the sustainable development of the potato industry. Using biocontrol strains to combat bacterial infections is considered an ideal approach. [Objective] We screened the phosphorus-solubilizing antagonistic strains of S. scabies and investigated their effects on the prevention and control of potato scab, aiming to provide candidate strains for the development of composite functional bacterial agents. [Methods] The target strains were screened by plate confrontation and phosphorus-solubilizing tests. Their taxonomic status was determined by morphological observation, physiological and biochemical tests, and 16S rRNA gene sequencing. Pot and field experiments were carried out to measure the inhibitory effects of the target strains on S. scabies, and the relationship between phosphorus-solubilizing function and antagonistic effect was analyzed. [Results] Four antagonistic strains BN4-4, BN4-5, BN5-2, and YN17-2, were screened out. Among them, BN4-4 and BN5-2 showed strong ability to degrade inorganic phosphorus. BN4-4 and BN4-5 were identified as Bacillus atrophaeus, while BN5-2 and YN17-2 as Bacillus subtilis. The pot experiments showed that the relative control effects of the four strains were 71.35%, 38.70%, 62.18%, and 36.22%, respectively. In the field experiments, BN4-4 and BN4-5 showed the control effects of 69.07% and 56.20%, respectively. The four strains exerted inhibitory effects on four plant pathogens: Alternaria solani, Fusarium oxysporum, Rhizoctonia solani, and Verticillium dahliae. The four strains showed tolerance to pH 1.0–13.0, NaCl concentration of 1%–13%, and high temperatures (up to 80 ℃). Furthermore, they were insensitive to commonly used fungicides such as avermectin, zhongshengmycin, thiophanate-methyl, kasugamycin, and carbendazim. All the four stains exhibited the ability to metabolize and produce indole-3-acetic acid (IAA), which has been shown to promote the growth and increase the yield of plants. Notably, strains BN4-4 and BN5-2 capable of solubilizing phosphorus exhibited stronger inhibitory effects on S. scabies than the non-phosphorus-solubilizing strains. [Conclusion] B. atrophaeus BN4-4 with phosphorus-solubilizing function demonstrated promising preventive effects against S. scabies. This strain demonstrated broad-spectrum disease resistance, thermal stability, salinity tolerance, plant growth-promoting effect, and colonizing ability, serving as a potential functional strain for preventing and controlling potato scab and other soil-borne diseases in crops.

Urothelial carcinoma of bladder (UCB) is a common malignant tumor of the urinary system and a common pathological type of bladder cancer (BC). With high morbidity, high mortality, and easy recurrence, UCB poses a serious threat to human health. The occurrence of UCB may be associated with smoking and exposure to toxic chemicals. With the deepening of research, researchers have discovered unique microbiota related to the occurrence and development of UCB in the bladder. This review focuses on the involvement of microbiota in the occurrence and development of UCB through urinary tract infection (UTI), affecting epithelial-mesenchymal transition (EMT), and up-regulating the expression of programmed cell death 1 ligand 1 (PD-L1). At the same time, this paper introduces the microbiota characteristics of healthy people and UCB patients as well as the prevention and treatment of UCB. By reviewing the relationship between microbiota and UCB, this paper provides new ideas for further clarifying the promoting effect of microbiota on UCB and developing drugs for treating UCB.