Mycobacterium tuberculosis (Mtb) ranks as the most lethal human pathogen, able to fend off repeated attacks by the immune system or medications. PE_PGRS proteins are hallmarks of the pathogenicity of Mtb and contribute to its antigenic diversity, virulence, and persistence during infection. M. smegmatis is a nonpathogenic mycobacterium that naturally lacks PE_PGRS and is used as a model to express Mtb proteins. PE_PGRS has the capability to evade host immune responses and enhance the intracellular survival of M. smegmatis. Despite the intense investigations into PE_PGRS proteins, their role in tuberculosis remains elusive. We engineered the recombinant M. smegmatis strain Ms-PE_PGRS38. The result shows that PE_PGRS38 is expressed in the cell wall of M. smegmatis. PE_PGRS38 contributes to biofilm formation, confers permeability to the cell wall, and shows variable responses to exogenous stresses. PE_PGRS38 downregulated TLR4/NF-κB signaling in RAW264.7 macrophages and lung tissues of infected mice. In addition, PE_PGRS38 decreased NLRP3-dependent IL-1β release and limited pathogen-mediated inflammasome activity during infection. Moreover, PE_PGRS38 inhibited the apoptosis of RAW264.7 cells by downregulating the expression of apoptotic markers including Bax, cytochrome c, caspase-3, and caspase-9. In a nutshell, our findings demonstrate that PE_PGRS38 is a virulence factor for Mtb that enables recombinant M. smegmatis to survive by resisting and evading the host’s immune responses during infection.

Background: The rapid emergence of antibiotic resistance in Acinetobacter baumannii has led the World Health Organization (WHO) to designate it as a “high priority” pathogen. The emergence of multidrug-resistant (MDR) and pandrug-resistant (PDR) strains poses considerable treatment challenges. As antimicrobial resistance (AMR) escalates toward a post-antibiotic era, innovative therapeutic solutions are urgently needed. Objectives: To clone, over-express, and characterize a novel endolysin, LysTAC1, from Acinetobacter phage TAC1 for its antibacterial efficacy against multidrug-resistant bacteria. Methods: A 24 kDa endolysin featuring a glycoside hydrolase Family 19 chitinase domain was tested against carbapenem-resistant Acinetobacter baumannii clinical isolates and various Escherichia coli strains following outer membrane permeabilization with Ethylenediaminetetraacetic acid (EDTA). Stability assays and molecular docking studies were performed. Results: LysTAC1 demonstrated potent lytic activity against Gram-negative bacteria but showed no activity against Gram-positive bacteria (Staphylococcus aureus ATCC 29213 and Enterococcus gallinarum HCD 28-1). LysTAC1 maintained activity across pH 6–9 and temperatures 4–65 °C, with differential sensitivity to metal ions where K⁺ showed no inhibitory effect at any concentration (0.1–100 mM), and Fe²⁺ was non-inhibitory at lower concentrations (0.1–1 mM), while Mg²⁺ and Ca²⁺ demonstrated concentration-dependent inhibition across the tested range (0.1–100 mM). Molecular docking revealed LysTAC1 interactions with chitinase substrates 4-nitrophenyl N-acetyl-β-D-glucosaminide and 4-nitrophenyl N, N-Diacetyl-β-D-chitobioside, with binding energies of −5.82 and −6.85 kcal/mol, respectively. Conclusions: LysTAC1 shows significant potential as a targeted therapeutic agent against A. baumannii with robust stability under physiological conditions.

Colorectal cancer (CRC) is the third most common cancer globally and the second leading cause of cancer-related deaths. While intestinal microbiota dysbiosis is linked to CRC, the direct role of intratumoral bacteria in metastasis remains poorly understood. In this study, we isolated pathogenic bacteria from CRC tumor tissues, identified as Hungatella hathewayi (H. hathewayi), through the 16S rRNA gene and whole-genome sequencing. We developed specific primers (P48/P52) and polyclonal antibodies for detecting H. hathewayi in samples. Using quantitative real-time PCR (qPCR), we found significant enrichment of H. hathewayi in fecal samples from CRC patients compared to healthy controls, with mean fold changes of 137-fold and 142-fold for primers P48 and P52, respectively. Analysis of tissue samples revealed that H. hathewayi abundance was higher in CRC tumor tissues compared to normal tissues, with mean fold changes of 2.90 for P48 and 3.97 for P52. Fluorescence in situ hybridization (FISH), immunofluorescence (IF), and immunohistochemistry (IHC) confirmed its spatial distribution within tumor tissues. In vitro assays using CRC cell lines demonstrated that H. hathewayi-derived succinate upregulates HIF-1α and SUCNR1 expression and promotes cell metastasis by inducing epithelial–mesenchymal transition (EMT). Collectively, these findings identify H. hathewayi as a novel pro-metastatic bacterium and a potential non-invasive biomarker for CRC diagnosis, providing direct evidence for the role of intratumoral bacteria in CRC progression.