Biology subjects

Nassif, X.

Publications and source records attributed to Nassif, X..

6 recordsLinked to original sources

bioRxiv2024

Structure of the virulence-associated Neisseria meningitidis filamentous bacteriophage MDA{varphi}

Neisseria meningitidis is a human commensal bacterium that can opportunistically invade the bloodstream and cross the blood-brain barrier, where it can cause septicaemia and meningitis. These diseases, if left untreated, can be lethal within hours. Hyperinvasive N. meningitidis strains often express a genomically encoded filamentous bacteriophage called MDA{Phi}, which promotes colonisation of mucosal host surfaces to facilitate invasion. How this phage is organised and how it promotes biofilm formation and infection at the molecular level is unclear. Here, we present an electron cryomicroscopy structure of the MDA phage, showing that MDA{Phi} is a class I filamentous inovirus, with the major capsid protein arranged within the phage as a highly curved and densely packed -helix. Comparison with other filamentous bacteriophages offers clues about inoviral genome encapsidation mechanisms, providing a framework for understanding the evolutionary diversity of inoviruses. A disordered, N-terminal segment in the major capsid protein presents hydrophobic patches on the surface of assembled phage particles, which, together with electron cryotomography data of phage bundles, furnishes a structural rationale for phage-phage interactions that were seen previously in an epithelium adhesion infection model of N. meningitidis. Taken together, our results shed light on the structure, organisation, and higher order assembly of a biomedically relevant phage encoded in the genome of a human pathogen. Molecular insights gleaned from this study increase our understanding of phage evolution, phage-mediated bacterial adhesion and pathogenicity.

microbiology↗

bioRxiv2024

A Toolbox for Neisseria meningitidis: Gene Editing, Complementation and Labelling

The efficient transformation of Neisseria meningitidis and Neisseria gonorrhoeae facilitates the rapid construction of bacterial mutants with insertion of antibiotic resistance cassettes. However, this strategy limits the construction of strains with multiple mutations. Recent advances in markerless strategies for Neisseria species have enabled the construction of mutants without antibiotic resistance markers. However, these innovative approaches have potential limitations related to the selection strategy or the possible occurrence of spontaneous mutations in the selection marker genes. In addition, complementation tools or labelling strategies for N. meningitidis are also lacking. In this study, we have introduced new tools for markerless mutation, genetic complementation and labelling in N. meningitidis, thus improving the research possibilities for understanding and tackling these pathogens.

microbiology↗

bioRxiv2023

NMA1982 is a Novel Phosphatase and Potential Virulence Factor in Neisseria meningitidis

Protein phosphorylation is an integral part of many cellular processes, not only in eukaryotes but also in bacteria. The discovery of both prokaryotic protein kinases and phosphatases has created interest in generating antibacterial therapeutics that target these enzymes. NMA1982 is a putative phosphatase from Neisseria meningitidis, the causative agent of meningitis and meningococcal septicemia. The overall fold of NMA1982 closely resembles that of protein tyrosine phosphatases (PTPs). However, the hallmark C(X)5R PTP signature motif, containing the catalytic cysteine and invariant arginine, is shorter by one amino acid in NMA1982. This has cast doubt about the catalytic mechanism of NMA1982 and its assignment to the PTP superfamily. Here, we demonstrate that NMA1982 indeed employs a catalytic mechanism that is specific to PTPs. Mutagenesis experiments, transition state inhibition, pH-dependence activity, and oxidative inactivation experiments all support that NMA1982 is a genuine phosphatase. Importantly, we show that NMA1982 is secreted by N. meningitidis, suggesting that this protein is a potential virulence factor. Future studies will need to address whether NMA1982 is indeed essential for N. meningitidis survival and virulence. Based on its unique active site conformation, NMA1982 may become a suitable target for developing selective antibacterial drugs.

biochemistry↗

bioRxiv2019

Air-interfaced colonization model suggests a commensal-like interaction of Neisseria meningitidis with the epithelium, which benefit from colonization by Streptococcus mitis.

Neisseria meningitidis is an inhabitant of the nasopharynx, from which it is transmitted from person to person or disseminates in the blood and becomes a harmful pathogen. In this work, we addressed the colonization of the nasopharyngeal niche by focusing on the interplay between meningococci and the mucus that lines the mucosa of the host. Using Calu-3 cells grown in air-interfaced culture, we studied the meningococcal colonization of the mucus and the host response. Our results suggested that N. meningitidis behaved like commensal bacteria in mucus, without interacting with human cells or actively transmigrating through the cell layer. As such, meningococci did not trigger a strong innate immune response from the Calu-3 cells. Finally, we have shown that this model is suitable for studying interaction of N. meningitidis with other bacteria living in the nasopharynx, and that Streptococcus mitis but not Moraxella catarrhalis can promote meningococcal growth in this model.

microbiology↗

bioRxiv2019

Transketolase is involved in the control of Sigma B during chronic infection by Staphylococcus aureus

Staphylococcus aureus is a leading cause of both acute and chronic infections in humans. The importance of the pentose phosphate pathway (PPP) during S. aureus infection is currently largely unexplored. Here, we focused on one key PPP enzyme, transketolase. We showed that inactivation of the unique gene encoding transketolase activity in S. aureus USA300 ({triangleup}tkt) led to drastic metabolomic changes. Using time-lapse video imaging and mice infection, we observed a major defect of the {triangleup}tkt strain compared to wild-type strain in early intracellular proliferation and in the ability to colonise kidneys. Transcriptional activity of the two master regulators Sigma B and RpiRc was drastically reduced in the {triangleup}tkt mutant during host cells invasion. The concomitant increased RNAIII transcription, suggests that TKT-or a functional PPP-strongly influences the ability of S. aureus to proliferate within host cells by modulating key transcriptional regulators.

microbiology↗

bioRxiv2018

Persistent Staphylococcus aureus infections in children with chronic lung disease: a multi-omics analysis of bacterial adaptation to define novel therapeutic approaches

BackgroundChronic lung infection of cystic fibrosis (CF) patients by Staphylococcus aureus is a well-established epidemiological fact. Indeed, S. aureus is the most commonly identified pathogen in the lungs of CF patients. Strikingly the molecular mechanisms underlying S. aureus persistency are not understood.\n\nMethodsWe selected pairs of sequential S. aureus isolates from 3 patients with CF and from one patient with non-CF chronic lung disease. We used a combination of genomic, proteomic and metabolomic approaches with functional assays for in-depth characterization of S. aureus long-term persistence.\n\nResultsFor the first time, we show that late S. aureus isolates from CF patients have an increased ability for intracellular survival in CFBE-F508del cells compared to ancestral early isolates. Importantly, the increased ability to persist intracellularly was confirmed for S. aureus isolates within the own patient F508del epithelial cells. An increased ability to form biofilm was also demonstrated.\n\nFurthermore, we identified the underlying genetic modifications inducing altered protein expression profiles and notable metabolic changes. These modifications affect several metabolic pathways and virulence regulators that could constitute therapeutic targets.\n\nConclusionsOur results strongly suggest that the intracellular environment might constitute an important niche of persistence and relapse necessitating adapted antibiotic treatments.\n\nSummaryS. aureus persists for years in the lungs of patients with cystic fibrosis despite antibiotic therapies. We demonstrate that S. aureus adaptation leads to increased intracellular persistence suggesting a key role for intracellular niche during S. aureus chronic lung infection.

microbiology↗