Inhibiting the synthesis of fungal cell wall is a safe and effective strategy for preventing and treating fungal infections. Chitin synthases are the key enzymes to catalyze the synthesis of chitin, an important structural component of fungal cell wall and septa. The roles of chitin synthases vary in regulating the synthesis of fungal chitin. This review outlines the roles of chitin synthases in regulating fungal cell proliferation, morphogenesis, interactions with hosts, and compensatory effect induced by cell wall damage in the three major pathogenic fungal species:Candida albicans,Aspergillus fumigatus, andCryptococcus neoformans, aiming to understand the importance of chitin synthases in fungal pathogenicity. Furthermore, this paper proposes a new antifungal strategy and the future research directions about the chitin synthases of fungi.

The α-herpesviruses are a large class of enveloped double-stranded DNA viruses characterized by neurotropic infection and latent infection, posing a serious threat to human and animal health. The α-herpesvirus genome encodes a variety of proteins.UL24, a major virulence gene of α-herpesviruses, encodes a highly conserved protein and play a key role in regulating viral infection. This paper introduced the basic characteristics ofUL24 and the encoded protein and summarized the regulatory roles of UL24 in the virus assembly, replication, infection, pathogenicity, and inhibition of host innate immunity, aiming to provide a theoretical reference for understanding the functions of α-herpesvirus proteins and further preventing and controlling α-herpesvirus infection.

[Objective] Streptomyces is a genus of Gram-positive aerobic bacteria characterized by complex morphological differentiation and potent secondary metabolite-producing ability. SapB, a class Ⅲ lanthipeptide, promotes the morphological differentiation ofStreptomyces coelicolor, which suggests that SapB-like peptides might be developed as targets for engineering of morphological differentiation. In this study, we characterized the effects of SapB-like peptides on the morphological differentiation of multipleStreptomyces species, aiming to provide a theoretical basis for the engineering of these peptides.[Methods] Bioinformatics tools were used to analyze the gene clusters for the synthesis of SapB-like peptides in the genomes ofStreptomyces spp.. The plasmids for heterologous expression were constructed and introduced intoStreptomyces spp. through conjugation. The colony and mycelial morphology were compared to reveal the effects of these peptides on the morphological differentiation ofStreptomyces.[Results] SapB-like peptides promoted the differentiation ofStreptomyces from vegetative to aerial mycelia. Specifically, they increased the aerial mycelia and accelerated the differentiation, thus shortening the morphological differentiation cycle.[Conclusion] SapB-like peptides can help shorten the morphological differentiation cycle ofStreptomyces, demonstrating the potential for the morphological differentiation engineering ofStreptomyces.

[Objective] To screen out a fungal strain that can efficiently assimilate ammonia nitrogen, reveal the metabolome differences of the strain in different media and the changes in the amino acid content of the feed fermented with the strain, and clarify the mechanism of its ammonia assimilation.[Methods] Seven strains ofTrichoderma, 7 strains ofAspergillus niger, and 9 strains ofAspergillus oryzae were cultured in the media with (NH₄)₂SO₄ as the only nitrogen source. The strains with high ammonia nitrogen use efficiency and glutamine synthetase (GS) activity were selected for comparison of the metabolic differences in potato dextrose agar (PDA) plates and inorganic nitrogen plates by non-targeted metabonomics. Furthermore, the crude protein and organic nitrogen content in the feed fermented with different strains was determined, and the changes in amino acid content in the fermented feed extract were measured by amino acid-targeted metabolomics.[Results] The utilization rate of ammonia nitrogen and the glutamine synthetase activity ofA. oryzae MQ28 were 54.46% and 0.61 μmol/(h·g), respectively, which were higher than those of other strains (P < 0.05). The comparative metabonomics analysis suggested that MQ28 was associated with the metabolism of multiple amino acids during ammonia assimilation. MQ28 fermentation increased the crude protein and organic nitrogen in the feed by 22.25% and 35.83% (P < 0.05), respectively. Furthermore, MQ28 fermentation increased the total amino acid content in feed extract from 31.86 mmol/100 g to 57.69 mmol/100 g (P < 0.05). Specifically, it increased the content of 14 amino acids such as threonine, lysine, and arginine, glutamic acid (by 3.46 folds), and glutamine (by 99 folds) (P < 0.05).[Conclusion] To sum up,A.oryzae MQ28 has high ammonia nitrogen utilization capacity. It may regulate the ammonia assimilation process through the synthesis of glutamine to regulate amino acid metabolism and can be used as an elite strain for the production of single-cell protein.

[Objective] This study aims to observe the changes of the fecal microbial communities in the dairy cows with subacute rumen acidosis (SARA) induced by a high-concentrate diet and modulated by the addition of vitamin E (VE). The potential effects on the metabolism of dairy cows were evaluated to provide data for exploring the physiological mechanisms of SARA.[Methods] Seven multiparous Holstein cows with rumen fistulas were selected for this trial which was carried out in three phases of 18 days each. The first phase was the control (CON) phase, with a concentrate-to-forage ratio of 50:50 in the diet (dry matter basis). The second phase was the induction (HG) phase, in which the forage was replaced with wheat flour at 15% of the diet (dry matter basis) to induce SARA. The third phase was the regulation (HGE) phase, in which VE was added at 12 000 IU/d/cow on the basis of the diet in the HG phase. The feces samples were collected on day 18 in each phase, and the microbial communities in the samples were examined.[Results] The fecal microbial community structure showed significant differences between three phases and the Shannon index in the HG phase was lower than that in the CON phase (P < 0.05). The HG phase had higher relative abundance ofProteobacteria andBlautia and lower relative abundance of unidentified_bacteria,Euryarchaeota,Desulfobacterota,Rikenellaceae_RC9_gut_group, andAlistipes than the CON phase (P < 0.05). The relative abundance ofBlautia in the HGE phase was higher than that in the HG phase (P < 0.05). The functional prediction results showed that SARA caused metabolic disorders in the dairy cows, while VE regulated the intestinal microbiota and health by improving the stability of microbial growth and promoting microbial reproduction.[Conclusion] The SARA induced by a high-concentrate diet led to reduced intestinal microbial diversity and metabolic disorders in dairy cows. VE can regulate intestinal health and maintain intestinal homeostasis by promoting the proliferation of beneficial intestinal microorganisms.

[Objective] To mitigate the threat of heavy metal pollution in wastewater to global food safety and human health, reduce the accumulation of lead (Pb) in soil, plants, and animals, and improve the removal rate of heavy metals by immobilizing microbial strains.[Methods] We carried out mixed strain test to select the white rot fungal strains with strong Pb²⁺ removal effects and excellent compatibility and explored the optimal strains and ratio for combination. Furthermore, we optimized the formula of the fungal strain composite and explored the optimal adsorption conditions of the composite in application.[Results] Phanerochaete chrysosporium,Coriolus versicolor,Lentinus sajor-caju, andPleurotus ostreatus with good compatibility were selected for subsequent experiments.C.versicolor mixed withL.sajor-caju at a volume ratio of 1:1 outperformed the single strains in removing Pb²⁺. The fungal strain composite composed of 20.0 g/L sodium alginate, 15.0 g/L biochar, 2.0×10⁶ CFU/mL white rot fungi, silica, and zeolite showed the Pb²⁺ removal rate of 90.63% within 96 h. Moreover, this composite had higher mechanical strength and strong resistance to mechanical shear. At the addition amount of 8.35 g/L and pH 5.64, the composite demonstrated the Pb²⁺ removal rate of 97.45% within 96 h. Moreover, this composite can be reused 7 times after adsorption-desorption-readsorption and maintained high Pb²⁺ removal capacity.[Conclusion] The immobilized white rot fungal strain composite can significantly improve the microbial utilization rate and wastewater treatment efficiency compared with single strains. It can greatly adsorb Pb²⁺ in wastewater under appropriate conditions within a short time and reduce the environmental threat caused by heavy metal pollutants. Therefore, the promotion of environmental protection greatly benefits from the use of immobilized mixed white rot fungal strains in the treatment of heavy metal-contaminated wastewater.

Retinoid acid-inducible gene-I-like receptor (RLR) signaling pathways, the immune signaling pathways in response to infections, play a regulatory role in the production of pro-inflammatory cytokines, chemokines, and type Ⅰ interferons. Ubiquitination as one of the post-translational modifications refers to the process of ubiquitin binding to different amino acid sites on the target proteins, which regulates the fates of proteins. For example, it initiates the proteasome pathway to degrade the target protein or activating the protein transport. The ubiquitination of RLR signaling pathways is a way of regulating multiple effectors and one of the classical pathways through which viruses induce major diseases in animals, autoimmune diseases, and chronic inflammation. This paper introduces the typical structural features and the ubiquitination types of key effectors in the RLR signaling pathways. Furthermore, it expounds the roles of ubiquitination in the regulation of key molecules in the RLR signaling pathways, aiming to provide a reference for the intervention or treatment of related diseases.

[Objective] To reveal the mechanisms ofPseudomonas putida Y-9 in actively regulating the extracellular and intracellular pH homeostasis during ammonia oxidation.[Methods] Y-9 was cultured in the nitrification media with initial pH 7.19 and 9.40, respectively, for 48 h. Metabolomics was employed to compare the differential metabolites and predict dissociation constant (pKa) during the ammonia oxidation. Transcriptomics was employed to compare the genes regulating.[Results] In the medium with initial pH 7.19, Y-9 produced maltitol to raise extracellular pH, and up-regulated the expression of the genes related to deaminase, deiminase, and cation transport to maintain intracellular pH stability. In the medium with initial pH 9.40, Y-9 produced acidic substances such as 5-aminovaleric acid 3 and oxamic acid to lower extracellular pH and regulated the expression of the genes associated with NADH dehydrogenase, cytochromes, ATP synthase, and amino acid transport to maintain intracellular acidity.[Conclusion] This study revealed the novel phenomenon of Y-9's extracellular pH stabilizing capacity and investigated its intracellular pH homeostasis mechanism. The findings enrich our knowledge about microorganism-environment interactions, and provide a theoretical basis for further understanding the pH stabilization mechanism in microbial denitrification processes.

[Objective] Bacillus thuringiensis (Bt), characterized by the massive production of insecticidal crystal proteins (ICPs) during sporulation, serves as the main strain resource for the commonly used and safe microbial insecticides. To further explore the mechanisms of sporulation and parasporal crystal formation and lay a theoretical foundation for the construction of efficient strains, we compared the transcriptomes of Bt at three important stages.[Methods] The transcriptomes of the hypervirulent strain Bt4.0718 at the middle vegetative growth stage (T1-10 h), the early sporulation stage (T2-20 h), and the late sporulation stage (T3-32 h) were compared. The representative differentially expressed genes (DEGs) were verified by real-time fluorescence quantitative PCR (qRT-PCR), and the phenotypes of the mutant strains with the knockout of specific functional genes were examined.[Results] The number of DEGs was 2 147 (T2/T1), 1 861 (T3/T1), and 1 708 (T3/T2), respectively. At T1, the medium was rich in nutrients, which served the sporulation and parasporal crystal formation. The high transcription levels ofkinA/D,spo0A/F, andsigE regulating sporulation played a role in the growth and development of the cells. The transcription of Cry1Ac, poly-hydroxybutyric acid (PHB), and hydroxybutanone (acetoin) were started at this time. The substantial formation of ICPs and spores occurred at T2 and T3, and the transcript levels of the regulatory genes were higher at T2 than those at T3. The genes associated with spore core/coat/cortex, germination protein, andspoII–spoVI began to be transcribed in large amounts at T2, with the highest levels among the three stages. The corresponding complex networks of carbohydrate, amino acid, and lipid metabolism, energy, nucleic acid, and peptide metabolism, secondary metabolite production, and environmental adaptation showed differences. In addition, as the physiological processes stimulated by nutrient signals, the two-component signal transduction system (TCS) and ABC transport system played an essential role in the process of sporulation and ICP transcription and expression, and their transcription levels were significantly different.[Conclusion] With the production of ICPs and sporulation, nutrients are gradually consumed, and the high expression ofsigB,sigW, andsigM contributed to the stability of cell wall and the resistance to environmental changes. Meanwhile, the small heat shock proteins Hsp20 and Hsp20B, as molecular chaperones, were also important for maintaining intracellular homeostasis and may facilitate the sporulation and ICP production.

[Objective] To explore the reasons for differences in the C-methylation programming of non-reducing polyketide synthases (NR-Pkss).[Methods] We used bioinformatics tools and AlphaFold 2 to compare the domain sequences and structures of the NR-Pkss involved in the synthesis ofMonascus pigment and citrinin inMonascus ruber M7, i.e., Mr-PksPT and Mr-PksCT. Furthermore, we employed molecular docking to compare the binding of C-methyltransferase domains (CMeTs) with other domains and the intermediates of the two NR-Pkss.[Results] The large differences of the overall structure and the high similarity of domain sequence and structure between the two NR-Pkss suggested that the differences of C-methylation programming between NR-Pkss may be resulted from domain interactions. The CMeT of Mr-PksCT was more likely to bind to the acyl carrier protein (ACP) carrying the substrate than that of Mr-PksPT, making the intermediate more easily catalyzed by CMeT. Moreover, CMeT had lower binding free energy to methyl receptor substrate than theβ-ketosynthase domain (KS).[Conclusion] The CMeTs of NR-Pkss can affect the C-methylation of the products by competing with KS. The findings provide a new idea for the study of C-methylation programming of Pkss.