Virulence最新文献

The diverse mycelial networks of fungi are generated through polar growth, cell division, and cell fusion. Most of the genes are well characterized as crucial for cellular communication and fusion processes in filamentous fungi, but their functions and molecular mechanisms remain poorly understood. Here, we functionally characterized the hyphal anastamosis protein 4 (AoHam4), hyphal anastamosis-8 protein (AoHam8) and serine/threonine protein phosphatase 2A (AoPP2A) in the model nematode-trapping fungus Arthrobotrys oligospora. Our results indicate that Aoham4, Aoham8 and Aopp2a genes are essential for hyphal fusion and trap morphogenesis, and modulate mycelial growth, conidial production, and pathogenicity in A. oligospora. Staining, RT-qPCR and transmission electron microscopy (TEM) results indicated that all three genes are involved in regulating reactive oxygen species (ROS) accumulation, lipid metabolism and autophagy processes. Moreover, RNA-Seq and liquid chromatography-mass spectrometry (LC-MS) experiments further confirmed that deletion of Aoham4, Aoham8 and Aopp2a genes affects transcription and metabolic levels. Yeast-two-hybrid (Y2H) analysis showed that AoPP2A can interact with AoSO (Soft, a fungus-specific scaffolding protein, is involved in signaling and secretion with the MAK-2 cascade). Since the ΔAoham8 mutant strain was more sensitive to cell wall-disrupting reagents, speculating that Aoham8 may regulate the mitogen-activated protein (MAP) kinase cascade response by activating the cell wall integrity pathway. Collectively, our studies illuminate the crucial roles of the fungal cell-fusion genes Aoham4, Aoham8 and Aopp2a in A. oligospora, as well as laying the groundwork for clarifying the mechanisms of mycelial development and trap morphogenesis of nematode-trapping fungi.

Streptococcus suis is a major cause of sepsis and meningitis in pigs, and zoonosis through the emergence of disease-associated lineages. The ability of S. suis to adapt and survive in host environments, such as blood and cerebrospinal fluid (CSF), is important for pathogenesis. Here, we used Transposon Sequencing (Tn-seq) coupled with Nanopore sequencing to identify conditionally essential genes (CEGs) for the growth of S. suis P1/7 in active porcine serum (APS) and CSF derived from choroid plexus organoids. To our knowledge, this is the first successful application of ONT to Tn-library screening, enabling rapid local runs and a publicly available analysis pipeline. Through comparative fitness analyses, we identified 33 CEGs that support growth in APS and 25 CEGs in CSF. These genes highlight the importance of pathways related to amino acid transport, nucleotide metabolism, and cell envelope integrity. Notably, the LiaFSR regulatory system and multiple ABC transporters were important for proliferation. We also identified several genes of unknown function as essential for growth, pointing to previously unrecognized genetic factors involved in S. suis adaptation during infection. These findings provide new insights into the genetic requirements for S. suis survival in host-like environments and a deeper understanding of its ability to adapt to distinct physiological niches.

Klebsiella pneumoniae invasive syndrome (KPIS), often arising from pyogenic liver abscesses, is characterized by metastatic infections and thrombotic complications. Diabetes mellitus (DM) is the most important risk factor for KPIS, as hyperglycemia promotes resistance of hypervirulent K. pneumoniae ;(hvKp) strains to phagocytosis and impairs neutrophil function. Given the interplay between platelet activation, inflammation, and thrombosis, aspirin, a well-established antiplatelet agent, has been associated with reduced incidence and recurrence of pyogenic liver abscesses in cohort studies. Platelets interact with neutrophils to form platelet - neutrophil aggregates (PNAs), which may contribute to KPIS pathogenesis. This study examined platelet - neutrophil interactions under hyperglycemic conditions using in vitro assays and in vivo models of diabetic mice infected with hvKp. High glucose concentrations significantly increased platelet activation, PNA formation, and bacterial survival. Salicylic acid, the bioactive metabolite of aspirin, reduced platelet activation and bacterial burden but did not impede PNA formation. Aspirin pre-treatment improved survival, reduced organ abscesses, and preserved tissue integrity in diabetic mice infected with hvKp. These results highlight the relationship between hyperglycemia, platelet activation, and immune dysregulation in KPIS, and support aspirin as a potential adjunctive therapy to mitigate thromboinflammatory complications of hvKp infection.

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.

Giardia duodenalis is an intestinal protozoan parasite responsible for giardiasis, a disease primarily characterized by diarrhea and associated with long-term complications such as malnutrition and growth impairment in children. The presence of Giardiavirus (GLV) has been shown to attenuate pathological damage in G. duodenalis-infected murine models and modulate distinct pro-inflammatory responses in host cells stimulated by Giardia. However, the understanding of the impact of the GLV on the G. duodenalis itself remains limited. Here, we found that GLV infection interfered with the host protein expression system by reducing both mRNA and protein levels of Giardia genes, while paradoxically enhancing mRNA translation efficiency. Additionally, GLV infection induced energy metabolic reprogramming in Giardia, as evidenced by the identification of 21 significantly altered energy metabolites. KEGG enrichment analysis revealed glycolysis/gluconeogenesis as the most prominently enriched metabolic pathway in GLV-infected Giardia. Notably, glycolysis continued to be upregulated with successive passages of GLV infection, even after the GLV load plateaued. The glycolytic enzyme enolase was found to be closely associated with GLV infection within Giardia, and morpholino-mediated knockdown of enolase expression resulted in a significant reduction in GLV replication. Overall, these findings demonstrate that GLV infection manipulates host translation and energy metabolic pathways to facilitate its persistence in G. duodenalis, and reveal both GLV and host metabolic targets as promising research subjects for developing drugs and vaccines for the prevention and treatment of giardiasis.

Bacterial metabolism is important for antibiotic resistance and tolerance. However, the impact of indole on bacterial metabolism and antibiotic efficacy has not been fully elucidated. In this study, we investigated the effect and specific mechanism of exogenous indole on the antibiotic susceptibility of Edwardsiella tarda, a common pathogen in freshwater and marine fish farming. We found that exogenous indole promoted E. tarda tolerance to the antibiotic florfenicol, and reprogrammed the E. tarda metabolome. A total of 108 metabolites were detected, including 66 differential metabolites that regulate various metabolic pathways, such as the tricarboxylic acid (TCA) cycle and nucleotide metabolism. Exogenous indole disrupted the TCA cycle in E. tarda by increasing the intracellular NADH contents and activating the respiratory chain to increase the reactive oxygen species levels, thereby increasing the intracellular Fe²⁺ content to activate the Fenton reaction, which in turn promotes the oxidative stress response. Furthermore, indole inhibited antibiotic entry into the cell and activated efflux pumps to reduce the intracellular antibiotic content, ultimately promoting antibiotic tolerance. In vivo, exogenous indole compromised the ability of florfenicol to protect fish survival and eliminate pathogenic bacteria. These results shed light on the metabolic changes induced by indole and suggest future directions for addressing antibiotic tolerance and clinical infections of E. tarda in aquaculture. This study serves as a reminder of the adverse effects of combining antibiotics with metabolites in aquaculture.

DDX17 (DEAD-box RNA helicase 17) is an essential RNA helicase and regulatory ATPase in host cells, extensively involved in various cellular processes during viral infections, such as RNA splicing, transcriptional regulation, and post-transcriptional modification. DDX17 exhibits dual functionality in viral infections: it enhances the stability, packaging, and replication of viral RNA through interactions with viral ribonucleoprotein complexes, as evidenced in infections caused by influenza viruses and Hantaan virus (HTNV). Conversely, DDX17 can inhibit viral proliferation by disrupting viral RNA metabolism, as observed in hepatitis B virus (HBV) and Epstein-Barr virus (EBV) infections, where it suppresses replication by modulating viral RNA decapping and degradation. The dual role of DDX17 provides novel insights into host-virus interactions while also highlighting its significant potential as an antiviral therapeutic target. These findings are expected to establish a theoretical foundation for related research and offer valuable references for developing novel antiviral strategies.

The oral cavity contains the second most diverse bacterial community after the intestines, with bacteria and viruses coexist. Streptococcus mutans is a major pathogenic bacterium in the oral cavity, commonly associated with dental caries. We investigated the effects of S. mutans-derived extracellular vesicles (Sm EVs) on herpes simplex virus 1 (HSV-1) infection, which is prevalent in the oral cavity. We performed our experiments in human oral keratinocyte (HOK) cells and mucosal tissue-derived organoids, and analyzed human whole saliva (n = 50) for associations between S. mutans and HSV-1 envelope glycoprotein D (gD) mRNA levels by qPCR. Sm EVs significantly enhanced HSV-1 production in mucosal organoids. Indeed, mRNA and/or protein levels of type I (IFN-α and IFN-β), type II (IFN-γ), and type III (IFN-λ₁, IFN-λ₂, and IFN-λ₃) interferons were significantly lower in Sm EV-treated mucosal organoids compared with the vehicle control under mock-infection. When HSV-1 was introduced after Sm EV pretreatment, these IFN levels showed a general trend of statistically significant reduction compared with those in the vehicle control. Moreover, Sm EVs suppressed IFN mRNA and protein levels by upregulating the EGFR - ERK pathway in mucosal cells, creating an environment that enhances HSV-1 production. Interestingly, a positive correlation was noted between S. mutans and HSV-1 detected in human whole saliva samples. These results suggest that S. mutans can negatively modulate the host innate antiviral responses by secreting EVs, thereby enhancing viral production. This study might provide a new perspective for controlling viral infections in humans.

Sindbis virus (SINV), a widely distributed alphavirus, is both a foundational model for viral replication studies and an underrecognized human pathogen. Despite its typically mild presentation, SINV can lead to prolonged joint pain and, in rare cases, neurological complications. This review explores SINV's molecular biology and clinical manifestations, particularly its role in causing Sindbis Fever - a self-limiting but potentially chronic arthritic disease. Molecular insights reveal mechanisms of immune evasion, neurovirulence, and persistent infection, highlighting SINV's potential for broader public health impact, especially under changing climatic conditions. This review also identifies key virulence determinants and discusses the virus's utility as a model for studying alphaviral encephalitis. Continued research is essential to better understand SINV pathogenesis and to prepare for potential outbreaks.