Virulence最新文献

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.

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.

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.

Porcine enteric coronaviruses, including porcine deltacoronavirus (PDCoV), porcine epidemic diarrhea virus (PEDV), swine acute diarrhea syndrome coronavirus (SADS-CoV), and transmissible gastroenteritis coronavirus (TGEV), can cause acute diarrhea, vomiting, dehydration, and high mortality in suckling piglets. Recent studies revealing human PDCoV infections and the potential of SADS-CoV to penetrate human cell lines have heightened apprehensions about the zoonotic transmission risks of these viruses. While heparan sulfate (HS) serves as a receptor in PDCoV binding, the key host genes involved in HS biogenesis and the specific molecular mechanisms underlying this process have not been fully examined. Enzymes involved in HS biosynthesis, including SLC35B2, EXT1, and NDST1, were identified as critical host factors via the use of CRISPR-Cas9 knockout cells. Moreover, inhibition assays using heparin sodium, a competitive HS mimic, demonstrated dose-dependent reductions in PDCoV infection in vitro. Additionally, mitoxantrone, an HS-binding drug, reduced PDCoV infection. Furthermore, HS was confirmed to facilitate the entry of other porcine enteric coronaviruses (SeCoVs), including PEDV, SADS-CoV, and TGEV, underscoring the conserved role of HS in CoV pathogenesis. These insights contribute to the understanding of porcine coronavirus-host interactions and support the development of innovative antiviral interventions.