Biology subjects

Faudry, E.

Publications and source records attributed to Faudry, E..

5 recordsLinked to original sources

bioRxiv2025

Avirulent Pseudomonas aeruginosa T3SS-negative strains belonging to Clade 5 produce variable quantities of secondary metabolites

Pseudomonas species are ubiquitous in the environment and serve as valuable source of enzymes and secondary metabolites for industrial applications. P. aeruginosa secretes metalloproteases such as elastase LasB and produces bioactive small molecules, including pyocyanin, rhamnolipids, and pyoverdine, with potential biotechnological applications. However, the interest in P. aeruginosa for industrial use has been limited due to the virulence-associated Type III Secretion System (T3SS), a key factor in host-pathogen interactions. In this study, we genotypically and phenotypically characterized a collection of P. aeruginosa strains naturally lacking T3SS-encoding genes. Phylogenetic analysis revealed that these strains belong to two distinct clades. Several strains exhibited low or no cytotoxicity on epithelial cell lines and were avirulent in the Galleria infection model. The level of LasB and the three metabolites -- pyocyanin, rhamnolipids, and pyoverdine -- varied independently of virulence profiles. Notably, we identified avirulent strains capable of producing at least two secondary metabolites, including monorhamnolipids, highlighting their potential for biotechnological applications.

microbiology↗

bioRxiv2024

Protective human monoclonal antibodies that target the Type III Secretion System of Pseudomonas aeruginosa inhibit translocon function

Pseudomonas aeruginosa is a major human opportunistic pathogen associated with a high incidence of multi-drug resistance. The antibody-based blockade of P. aeruginosa virulence factors represents a promising alternative strategy to mitigate its infectivity. In this study, we employed single B cell sorting from cystic fibrosis patients to isolate human monoclonal antibodies (mAbs) targeting proteins from the P. aeruginosa Type 3 Secretion System (T3SS) and characterized a panel of mAbs directed at PscF and PcrV. Among those, two mAbs, P5B3 and P3D6, that bind to the injectisome tip protein PcrV, exhibited T3SS blocking activity. We solved the crystal structure of the P3D6 Fab-PcrV complex, which revealed that the Ab binds to the C-terminal region of PcrV. In addition, we compared the T3SS-blocking activity of three PcrV-targeting mAbs, including two from previous independent studies, using two distinct assays to evaluate pore formation and toxin injection. We conducted a mechanistic and structural analysis of their modes of action through modeling based on the known structure of a functional homolog, SipD from Salmonella typhimurium. The analysis suggests that anti-PcrV mAbs may act through different mechanisms, ranging from preventing PcrV oligomerization to disrupting PcrVs scaffolding function, thereby inhibiting the assembly and function of the translocon pore. Our findings provide additional evidence that T3SS-targeting Abs, some capable of inhibiting virulence, are elicited in P. aeruginosa-infected patients. The results offer deeper insights into PcrV recognition by mAbs and their associated mechanisms of action, helping to identify which Abs are more likely to be therapeutically useful based on their mode of action and potency. This paves the way for the development of effective alternatives to traditional antibiotics in the fight against this resilient pathogen.

microbiology↗

bioRxiv2022

Aquatic long-term persistence of Francisella tularensis ssp. holarctica is driven by water temperature and transition to a viable but non-culturable state

Francisella tularensis is a highly virulent bacterium causing tularemia zoonosis. An increasing proportion of infections occur through contaminated hydro-telluric sources, especially for the subspecies holarctica (Fth). Although this bacterium has been detected in several aquatic environments, the mechanisms of its long-term persistence in water are not yet elucidated. We evaluated the culturability and the viability of a virulent Fth strain in independent microcosms filled with nutrient-poor water. At 37{degrees}C, the bacteria remained culturable for only one week, while culturability was extended to 6 weeks at 18{degrees}C and up to 11 weeks at 4{degrees}C. However, while the viability of the bacteria declined similarly to culturability at 37{degrees}C, the viability of the bacteria remained stable overtime at 18{degrees}C and 4{degrees}C for more than 24 months, long after loss of culturability. We identified water temperature as one of the major factors driving the aquatic survival of Fth through a transition of the whole Fth population in a viable but non-culturable (VBNC) state. Low temperature of water ([≤]18{degrees}C) favors the persistence of the bacteria in a VBNC state, while a temperature above 30{degrees}C kills culturable and VBNC Fth bacteria. These findings provide new insights into the environmental cycle of Francisella tularensis that suggest that the yet unidentified primary reservoir of the subspecies holarctica may be the aquatic environment itself in which the bacteria could persist for months or years without the need for a host.

microbiology↗

bioRxiv2020

The PopN gate-keeper complex acts on the ATPase PscN to regulate the T3SS secretion switch from early to middle substrates in Pseudomonas aeruginosa

Pseudomonas aeruginosa is an opportunistic bacterium of which the main virulence factor is the Type III Secretion System. The ATPase of this machinery, PscN (SctN), is thought to be localized at the base of the secretion apparatus and to participate in the recognition, chaperone dissociation and unfolding of exported T3SS proteins. In this work, a protein-protein interaction ELISA revealed the interaction of PscN with a wide range of exported T3SS proteins including the needle, translocator, gate-keeper and effector. These interactions were further confirmed by Microscale Thermophoresis that also indicated a preferential interaction of PscN with secreted proteins or protein-chaperone complex rather than with chaperones alone, in line with the release of the chaperones in the bacterial cytoplasm after the dissociation from their exported proteins. Moreover, we suggest a new role of the gate-keeper complex and the ATPase in the regulation of early substrates recognition by the T3SS. This finding sheds a new light on the mechanism of secretion switching from early to middle substrates in P. aeruginosa. HighlightsO_LIT3SS substrates are secreted sequentially but information on the switches are missing C_LIO_LIInteraction of the T3SS ATPase with secreted proteins were investigated by different approaches C_LIO_LIMicroscale Thermophoresis revealed a lower affinity for chaperones alone compared to complexes C_LIO_LIThe Gate-keeper complex binds to the ATPase and increases its affinity for the needle complex C_LIO_LIA new role of the Gate-keeper complex is proposed, directly acting on the T3SS ATPase C_LI O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=103 SRC="FIGDIR/small/224923v2_ufig1.gif" ALT="Figure 1"> View larger version (15K): org.highwire.dtl.DTLVardef@1e6803corg.highwire.dtl.DTLVardef@1ed155aorg.highwire.dtl.DTLVardef@14faf6org.highwire.dtl.DTLVardef@1685ec8_HPS_FORMAT_FIGEXP M_FIG C_FIG

biochemistry↗

bioRxiv2017

CLIQ-BID: A method to quantify bacteria-induced damage to eukaryotic cells by automated live-imaging of bright nuclei

Pathogenic bacteria induce eukaryotic cell damage which range from discrete modifications of signalling pathways, to morphological alterations and even to cell death. Accurate quantitative detection of these events is necessary for studying host-pathogen interactions and for developing strategies to protect host organisms from bacterial infections. Investigation of morphological changes is cumbersome and not adapted to high-throughput and kinetics measurements. Here, we describe a simple and cost-effective method based on automated analysis of live cells with stained nuclei, which allows real-time quantification of bacteria-induced eukaryotic cell damage at single-cell resolution. We demonstrate that this automated high-throughput microscopy approach permits screening of libraries composed of interference-RNA, bacterial strains, antibodies and chemical compounds in ex vivo infection settings. The use of fluorescently-labelled bacteria enables the concomitant detection of changes in bacterial growth. Using this method named CLIQ-BID (Cell Live Imaging Quantification of Bacteria Induced Damage), we were able to distinguish the virulence profiles of different pathogenic bacterial species and clinical strains.

microbiology↗