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Influenza A viruses (IAVs) pose a significant threat to global health, causing annual epidemics and occasional pandemics with substantial morbidity and mortality. Despite the availability of vaccines and antiviral therapies, the development of novel preventive and therapeutic strategies remains a critical research focus. In this study, we evaluated the protective effects of orally administering Escherichia coli Nissle 1917 in IAV-infected mice and elucidated its mechanisms of action by analyzing cecal microbiota and plasm metabolome profiles. Oral administration of E. coli Nissle 1917 alleviated respiratory symptoms, reduced weight loss, and mitigated pathological injury in mice infected with H9N2 or H1N1 IAV. These protective effects were mediated through the modulation of gut microbiota diversity, which increased the abundance of Bacteroides and Akkermansia, correlating with elevated pipecolic acid levels and ultimately aiding in defense against IAV infection in mice. Notably, we identified that the circulating metabolic molecule pipecolic acid plays a significant role in fighting IAV infection. Our findings suggest the potential usefulness of E. coli Nissle 1917 or pipecolic acid in influenza prevention.

Diffusible signal factor (DSF)-family quorum sensing (QS) signals are widely utilized by many pathogenic bacteria to modulate various biological functions and virulence. Previous studies showed that cis-2-decenoic acid (cis-DA) is involved in the modulation of biofilm dispersion in Pseudomonas aeruginosa, but the regulatory mechanism is unclear. Here, we report that cis-DA regulates the physiology and virulence of P. aeruginosa through FadD1, a long-chain fatty acid-CoA ligase. cis-DA specifically binds to FadD1 and enhances the binding ability of FadD1 to the target gene promoter DNA regions. Further analysis showed that FadD1 is a global regulatory factor that controls the transcription of various target genes. Moreover, FadD1 showed catalytic activity on cis-2-dodecenoic acid (BDSF) of Burkholderia cenocepacia and enhanced the competitiveness of P. aeruginosa. Together, our work presents a new DSF-type QS signaling system in P. aeruginosa, which is highlighted by the signal receptor evolved from a canonical enzyme of fatty acid metabolism.

Staphylococcus aureus is a notorious opportunistic pathogen with remarkable adaptability, enabling it to infect virtually every human tissue. Staphyloxanthin (STX), a critical virulence factor, contributes to S. aureus oxidative damage. However, the regulatory mechanism of STX production is incompletely understood. This study provides mechanistic insights into the role of catabolite control protein A (CcpA) in STX production. ccpA deletion considerably reduced STX yield in S. aureus strains with diverse genetic lineages. Western blot showed that CcpA inactivation did not alter SigB expression levels in S. aureus. Gene reporter and electrophoretic mobility shift assays revealed the direct control of CcpA on the expression of the crtOPQMN operon, which encodes enzymes for step-wise STX biosynthesis. Moreover, CcpA deficiency remarkably impaired bacterial tolerance to H₂O₂-mediated killing, decreased survival in whole-blood treatment, and diminished persistence in macrophages. In mouse bacteremia and skin abscess models, CcpA was shown to enhance S. aureus virulence. Notably, inhibition of CcpA with Ag⁺ synergized with vancomycin to combat vancomycin-intermediate S. aureus infections in vivo. Our findings establish CcpA as a SigB-independent regulator of STX production, suggesting that targeting CcpA could be a promising antibiotic synergistic strategy for the management of multidrug-resistant S. aureus infections.

Perinephric abscess, a common complication after kidney transplantation, often results from drug-resistant bacterial infections and is notoriously difficult to treat. Phage therapy has emerged as a promising alternative for such resistant infections. Here, we present two cases of perinephric abscesses in kidney transplant recipients (KTRs) treated with phage therapy. Our findings highlight the need for personalized treatment plans and timely intervention with phage therapy to improve patient outcomes. Future research should focus on overcoming barriers like biofilms to make this treatment more effective. Ultimately, phage therapy could lead to better survival rates and improved quality of life for transplant patients facing severe infections. This study is a step forward in the fight against superbugs, offering a potential alternative when antibiotics fail.

Coxiella burnetii, the etiological agent of Q fever, is a significant intracellular bacterial pathogen. C. burnetii is a highly infectious pathogen that primarily targets pulmonary alveolar macrophages during natural infection. It can then disseminate to macrophages in other tissues and organs, leading to chronic infections. C. burnetii is capable of infecting a variety of cultured cells, including primary macrophages, macrophage-like cells, epithelial cells, and fibroblasts. The virulence of C. burnetii is entirely dependent on the Dot/Icm type IVB secretion system (T4BSS), which delivers effectors into infected cells to modulate cellular pathways for the biogenesis of the Coxiella-containing vacuole that supports its intracellular replication. A deeper understanding of how C. burnetii exploits host cell processes is essential for developing novel therapeutic strategies to combat infections caused by this important pathogen. This review summarizes the historical milestones and recent advances in our understanding of the structure and function of the C. burnetii Dot/Icm system and its effectors.

The tubulin-like protein FtsZ assembles into the Z ring that leads to the assembly and activation of the division machinery in most bacteria. ZapA, a widely conserved protein that interacts with FtsZ, plays a pivotal role in organizing FtsZ filaments into a coherent Z ring. Previous studies revealed that ZapA forms a dumbbell-like tetramer that binds cooperatively to FtsZ filaments and aligns them in parallel, leading to the straightening and organization of FtsZ filament bundles. However, how ZapA interacts with FtsZ remains obscure. Here, we reveal that ZapA uses a two-pronged mechanism to interact with FtsZ to facilitate Z ring formation in Escherichia coli. We find that mutations affecting surface-exposed residues at the junction between adjacent FtsZ subunits in a filament as well as in an N-terminal motif of FtsZ weaken its interaction with ZapA in vivo and in vitro, indicating that ZapA binds to these regions of FtsZ. Consistent with this, ZapA prefers FtsZ polymers over monomeric FtsZ molecules and site-specific crosslinking confirmed that the dimer head domain of ZapA is in contact with the junction of FtsZ subunits. As a result, disruption of the putative interaction interfaces between FtsZ and ZapA abolishes the midcell localization of ZapA. Taken together, our results suggest that ZapA tetramers grab the N-terminal tails of FtsZ and bind to the junctions between FtsZ subunits in the filament to straighten and crosslink FtsZ filaments into the Z ring.

Among the 14 serovars of Listeria monocytogenes (Lm), serovar 4b strains are the most predominant isolates linked to human listeriosis outbreaks-a phenotype associated with their unique wall teichoic acid (WTA) decorated with galactose (Gal) and glucose (Glu). A wealth of knowledge is available for galactosylated-WTA (Gal-WTA) manipulating bacterial homeostasis and virulence, whereas the relationship between glucosylated-WTA (Glu-WTA) and Gal-WTA in listerial physiology and pathogenesis remains unclear. Here, we find that Glu-WTA and Gal-WTA jointly constitute the O-antigen pattern of serovar 4b Lm; however, Glu-WTA specifically serves as the indispensable ligand for listeriophage LP4 adsorption. Moreover, the co-operation between Glu- and Gal-WTA increases biofilm formation and bacterial resistance to cationic antimicrobial peptide (CRAMP). We further demonstrate that Gal-WTA modulates the anchoring of surface proteins, including IspC, Ami, and InlB. Additionally, dual glycosylated WTA interaction with ActA facilitates bacterial intracellular motility and dissemination. Consistently, Glu-WTA significantly enhances bacterial colonization ability in the mesenteric lymph nodes (MLNs), ileum, liver, and brain of mouse, cooperating with Gal-WTA to facilitate Lm dissemination to distant organs and tissues. In conclusion, we reveal the crucial roles of Glu-WTA in synergizing with Gal-WTA to modulate the integrity of the cell wall structure and exacerbate bacterial infection, providing a global understanding of the hypervirulence and pathogenicity of invasive serovar 4b Lm.

The CRISPR-Cas9 system has been proven to be a powerful tool for gene editing in living cells and shows great potential in genetic disease treatment. Anti-CRISPR (Acr)-based optogenetic tools could spatiotemporally regulate the activity of CRISPR-Cas9, thereby improving the precision and safety of gene editing. However, these tools could only regulate a certain Cas9 protein because of the high specificity of Acr used, limiting their further application. In this study, we developed a new optogenetic tool named CASANOVA-A5 (CRISPR-Cas9 activity switching via a novel optogenetic variant of AcrIIA5) by inserting the blue light sensor AsLOV2 into AcrIIA5 with a broad inhibition spectrum. We proved that the CASANOVA-A5 could regulate the gene editing activity of SpCas9, SaCas9, NmeCas9, and St1Cas9 in a blue light-dependent manner. Additionally, we engineered AcrIIA5-LOV9 by integrating the blue light-dependent degron module LOV9, showing obvious optical regulation for SpCas9. Together, our work demonstrates two feasible methods to engineer the Acrs to potent optogenetic tools and suggests systematic strategies for further optimization.

COVID-19 remains an ongoing threat to public health, and reliable, continuous disease monitoring programs are essential for preventing future surges of infection. However, without mandated COVID-19 testing, accurate data of confirmed cases are unavailable. Instead, COVID-19 viruses may be tracked via wastewater samples from sewage manholes in areas of high social connectivity, where captured viral RNA data are biomarkers useful for monitoring and predicting community-level COVID-19 prevalence through machine learning techniques. We construct a prediction model of high sensitivity and specificity to provide evidence of significant underreporting of COVID-19 cases for the time period following the lifting of testing mandates.