Virulence最新文献

Camellia oleifera is an important economic woody oil plant in many Asian countries, and the anthracnose caused by Colletotrichum fructicola is prevalent in its cultivation regions, causing significant losses annually. We previously found that CfGcn5-mediated H3 acetylation governs virulence of C. fructicola. To further elucidate the regulatory mechanism of CfGcn5, we carried out mass spectrometry analysis for CfGcn5-interacting proteins and identified CfAda3 protein for functional analysis. We found that CfAda3 was mainly localized in nucleus and cooperated with CfGcn5 to acetylate H3K18 for global gene transcription. Targeted gene deletion revealed that CfAda3 is involved in growth and conidiation. Similar to ΔCfgcn5 mutant, the ΔCfada3 mutant is defective in conidial germination, appressorial formation, autophagy, and in the response to environmental stresses. These combined effects result in its non-virulence on C. oleifera. In addition, we provided evidence showing that both NLS region and ADA3 domain are required for the localization and function of CfAda3. Moreover, we indicated that the interaction with CfGcn5 is essential but not sufficient for the normal localization and full function of CfAda3. Taken together, our studies not only illustrate the prominent roles of CfAda3 in growth, development, and virulence but also highlight how CfAda3 functions together with CfGcn5 in C. fructicola.

Porcine reproductive and respiratory syndrome virus(PRRSV) is an economically important pathogen for global pork industry. As a positive-strand RNA virus, lacking exonuclease-mediated proofreading, its RNA-dependent RNA polymerase (RdRP) domain within the nonstructural protein 9(nsp9) plays a vital role in maintaining replication accuracy. To identify the residues of PRRSV that regulates replication fidelity, its RdRP structure was predicted by using Alpha Fold 2 and aligned with the solved structure of coxsackievirus B3 (CVB3) RdRP. This comparison identified conserved residues in PRRSV RdRP that are potentially involved in fidelity. Using site-directed mutagenesis, nucleoside analog sensitivity tests, and next-generation sequencing(NGS), it was found that the nsp9 K541R mutation enhances fidelity, as increasing viral resistance to mutagens like ribavirin, 5-Fluorouracil(5-FU), and 5-Azacytidine(5-AZC), as well as generating lower rate of non-contiguous junctions. In contrast, mutations at other positions, including A394G, L396S, and R401A, reduced fidelity and elevated frequency of recombination and mutation accumulation. Structural modeling revealed that the highly conserved residue K336 is spatially adjacent to the key fidelity site K541 but situated on the opposite side of the RNA channel. We found that K336R exhibits a dissociated "resistance-high recombination" phenotype. The findings reveal the importance of specific residues in PRRSV RdRP for replication fidelity and provide insights into the potential for improving the stability and safety of live attenuated vaccines through targeted modifications. Furthermore, the study emphasizes the structural conservation of fidelity determinants across RNA viruses, despite low sequence similarity, which can offer a framework for identifying fidelity key sites in other viral RdRPs.

Peronophythora litchii is an oomycete pathogen responsible for litchi downy blight, a significant threat to global litchi production. Autophagy, a conserved degradation pathway crucial for the growth, development, and pathogenicity of phytopathogenic organisms, remains an area of active investigation. In this study, we characterized the function of the Atg26 homolog PlAtg26b in P. litchii. Using the CRISPR/Cas9 genome editing system, we generated PlATG26b knockout mutants and determined that PlAtg26b localizes to mitochondria under stress conditions. Although deletion of PlATG26b did not impair selective autophagy, it markedly reduced Atg8-PE synthesis, vegetative hyphal growth, asexual and sexual reproduction, and zoospore release. Furthermore, PlATG26b-deficient mutants exhibited significantly reduced virulence on litchi fruits and leaves. Collectively, our findings demonstrate that PlAtg26b plays a pivotal role in the biological development and pathogenicity of P. litchii.

Transfer messenger RNA (tmRNA), a key component of the trans-translation system, plays an essential role on the virulence of pathogenic bacteria. However, the upstream regulatory mechanisms that regulate tmRNA expression remain largely unexplored. In this study, AraC superfamily regulator (AsfR) was found to directly interact with the promoter of ssrA gene, which encodes tmRNA. Co-transformation of the reporter construct, consisting of tmRNA promoter fused to enhanced green fluorescent protein (eGFP), alongside an AsfR expression vector, resulted in increased fluorescence, indicating that AsfR positively regulates mRNA expression. Consistently, the transcription level of tmRNA was significantly decreased in ΔasfR compared with WT of A. veronii by quantitative real-time PCR (RT-qPCR) analyses. The ΔasfR and ΔtmRNA mutants exhibited significantly reduced motility and biofilm formation. Reduced transcription of the flagellar gene fliE in both mutants suggests that the AsfR/tmRNA axis may regulate these processes via fliE. Furthermore, deletion of asfR and tmRNA impairs oxidant resistance and pathogenicity, resulting in growth inhibition in A. veronii. This study elucidates the regulatory role of the AsfR-tmRNA pathway in flagellar motility, biofilm formation, and antioxidant capacity, all of which contribute to bacterial virulence and provide potential targets for the treatment of bacterial infections.

Microsporidia, ubiquitous obligate intracellular parasites infecting a wide range of hosts from humans to economically vital animals, employ transovarial transmission (TOT) as their primary vertical transmission mode. Despite its significance, the mechanisms underpinning microsporidian TOT have remained elusive. This study comparatively analyzed the TOT in two distinct systems: Nosema pernyi infecting wild tussah Antheraea pernyi, and Nosema bombycis infecting domestic silkworms Bombyx mori and crop pests Spodoptera litura and Helicoverpa armigera. Our findings reveal that both parasites share a conserved invasion sequence targeting ovariole sheath cells, follicular cells, nurse cells, and ultimately oocytes. Notably, infection of follicular and nurse cells consistently precedes oocyte invasion, suggesting a strategic utilization of these cells for efficient transmission. Contrasting patterns were observed between the two parasites: while N. bombycis exhibits lower infection rates and produces mature spores in both oocytes and nurse cells, N. pernyi displays higher parasite loads with proliferative stages predominant throughout infection. A critical innovation emerges from our RNA interference experiments, where knockdown of host vitellogenin (Vg) significantly reduced microsporidian loads, identifying Vg as a conserved molecular facilitator in TOT. These findings not only elucidate the evolutionary conservation of vertical transmission mechanisms among microsporidia but also pinpoint Vg as a promising target for intervention against these pathogens. This research advances our understanding of vertical transmission of fungal parasites and offers novel avenues for disease control.

Haemophilus parainfluenzae (Hpar) is a common colonizer found in the upper respiratory tract, although recently urogenital colonization has emerged as a clinical concern. Urogenital Hpar has been associated with increased antibiotic resistance and virulence compared to respiratory Hpar. We analyzed the genome of 270 Hpar isolates, including all sequencing data found in the NCBI sequence read archive database. The pangenome of respiratory and urogenital isolates were compared in order to find potential metabolic or pathogenic adaptations to different host environments. The pangenome-wide association study found significant genomic differences. Specifically, the two-component signal transduction system was significantly enriched in urogenital samples, which could explain the adaptations of Hpar to the unique physico-chemical conditions of the urethra. Additionally, the two-component system could work as a new target for antimicrobials against pathogenic Hpar. The polysaccharide capsule, the main virulence factor in Haemophilus spp. was present in 26/65 of the urogenital samples from our facility, an increase from previous studies. In summary, the data presented suggest that respiratory and urogenital isolates of Hpar belong to different genetic lineages, and therefore it is possible that unprotected oral sex is not the route of transmission of Hpar from the respiratory tract to the urethra. Given the limited amount of available sequences, future studies collecting more isolates from different spatiotemporal locations would shed more light on this issue.

Salmonella enteritidis is a globally prevalent zoonotic pathogen with a broad host range and high pathogenicity, ranking among the most common serotypes within the Salmonella genus. The widespread and often indiscriminate use of antibiotics has driven a continual rise in antimicrobial resistance among S. Enteritidis strains, posing a significant threat to public health. In this study, we employed a quantitative proteomics approach to investigate differential protein expression between meropenem-sensitive and -resistant S. Enteritidis strains. Bioinformatic analyses revealed significant downregulation of all the genes associated with the bacterial chemotaxis pathway in the resistant strain. To further explore the functional relevance of this pathway, we generated deletion mutants of 15 chemotaxis-related genes and assessed their susceptibility to meropenem. Notably, deletion of the mglB gene was associated with increased resistance. Given the known role of mglB in galactose transport, we hypothesized and subsequently confirmed that exogenous galactose supplementation enhances the bactericidal activity of meropenem against resistant strains. This synergistic effect was further validated in animal infection models. Collectively, these findings provide novel insights into the molecular basis of meropenem resistance in S. Enteritidis and highlight the potential of metabolic modulation as a strategy to restore antibiotic efficacy.

Avian infectious bronchitis virus (IBV) belongs to the genus Gammacoronavirus (family Coronaviridae), causes severe multi-system disease in chickens, inflicting major global economic losses. The molecular interplay between IBV and host metabolic networks remains poorly understood. Through integrated transcriptomic, metabolomic, and lipidomic profiling of oviduct tissues from specific-pathogen-free (SPF) chickens infected with the IBV QXL strain, we demonstrate tripartite metabolic reprogramming: 1) redirected glucose flux through the pentose phosphate pathway (PPP) to fuel nucleotide synthesis, 2) rewired lipid metabolism to prioritize de novo membrane biogenesis over fatty acid β-oxidation, and 3) orchestrated glycerophospholipid remodeling. This integrated analysis revealed a coordinated upregulation of fatty-acid biosynthesis genes and accumulation of specific glycerophospholipids and eicosanoids. Mechanistically, IBV co-opts the Warburg effect and PPP activation while uniquely suppressing fatty acid β-oxidation to channel fatty acids toward lipid droplets (LDs) biogenesis. Phosphatidylserine (PS) overproduction (e.g. 2.55-fold increase in PS(22:0/22:6)) and phospholipase A₂ (PLA₂)-mediated lysophospholipids (Lyso-PLs) and eicosanoids generation (e.g. 7.09-fold increase in prostaglandin E₂ (PGE₂)) emerged as critical regulators of membrane dynamics and inflammatory signaling. This process was centrally coordinated by the significant activation of peroxisome proliferator-activated receptor (PPAR) (e.g. 1.74-fold increase in ACSL1) and transforming growth factor-beta (TGF-β) (e.g. significant increase in p-SMAD2) signaling pathways, directly linking lipid remodeling to immunomodulation. Functionally, targeting acetyl-CoA carboxylase (ACC) or glucose-6-phosphate dehydrogenase (G6PD), alongside TGF-β pathway modulation, synergistically curtailed viral replication in vitro. Our findings delineate a critical PPAR-TGF-β cross-talk that governs lipid remodeling during infection and identify host metabolic nodes that are potentially targetable for antiviral intervention.

Calf diarrhea, particularly that caused by diarrheagenic Escherichia coli, has become a major issue affecting the sustainable development of the calf farming industry. Although the use of traditional antimicrobial agents can alleviate symptoms, challenges such as antibiotic resistance, drug residues, and intestinal microbiota dysbiosis urgently need to be addressed. Therefore, this study investigates the mechanism by which compound probiotics alleviate diarrheagenic Escherichia coli-induced diarrhea in calves. Compound probiotics were administered to calves with diarrheagenic Escherichia coli-induced diarrhea, and their effects on growth performance, intestinal microbiota structure, and metabolic profiles were evaluated. The results showed that compound probiotic intervention significantly improved calf growth performance and weight gain. Integrated 16S rRNA sequencing and metabolomics analyses revealed that compound probiotic intervention markedly modulated the intestinal microbiota, particularly by increasing the abundance of the genus Blautia, while also improving tryptophan and bile acid metabolic pathways. Furthermore, fecal microbiota transplantation experiments conducted in both calves and antibiotic-induced microbiota depletion mouse models confirmed the regulatory effects of compound probiotics on the intestinal microbiota, especially with respect to tryptophan and bile acid metabolism. Compound probiotic intervention regulated key metabolites, including kynurenic acid, taurodeoxycholic acid, and ursodeoxycholic acid, which were positively correlated with Blautia, and significantly reduced inflammation by downregulating pro-inflammatory factors and upregulating anti-inflammatory factors, thereby alleviating diarrheagenic Escherichia coli-induced diarrhea in calves. Overall, this study provides new insights into the application of probiotics in intestinal health management and highlights the significant potential of compound probiotics as an alternative to antibiotics for the treatment of calf diarrhea.

Infections with Streptococcus pyogenes are among the most important diseases caused by bacteria and are responsible for around 500,000 deaths every year. In 2024, macrolide-resistant S. pyogenes was added to the WHO's list of priority pathogens. The non-phosphorylating glyceraldehyde-3-phosphate dehydrogenase GapN has been identified as a potential drug target in S. pyogenes. SpyGapN is the major NADP-reducing enzyme in these bacteria as they lack the oxidative part of the pentose phosphate pathway. In this study, in silico docking of compound libraries to the glyceraldehyde 3-phosphate binding pocket of SpyGapN was used to screen for potential competitive inhibitors. Among the candidates identified with this approach, 1,2-dihydroxyethane-1,2-disulfonate (glyoxal bisulfite) showed the strongest inhibition of SpyGapN activity in vitro. In a complementary approach, crystallographic fragment screening was conducted, which identified the ultra-low-molecular-weight compounds pyrimidine-5-amine and 4-hydroxypyridazine targeting the cofactor-binding pocket of SpyGapN. Both low-molecular-weight compounds were experimentally confirmed to inhibit the activity of purified SpyGapN. Combinations of glyoxal bisulfite with either pyrimidine-5-amine or 4-hydroxypyridazine enhanced the inhibitory effect of SpyGapN. Glyoxal bisulfite was able to kill S. pyogenes. This effect was accelerated by combining glyoxal bisulfite with 4-hydroxypyridazine. While these findings suggest that inhibition of SpyGapN probably contributes to the observed antibacterial activity, the exact mechanism of action remains to be confirmed, as the compounds also affect other G3P-converting enzymes. Nevertheless, these compounds provide a promising starting point for the development of more specific SpyGapN inhibitors.