Biology subjects

Chapot-Chartier, M.-P.

Publications and source records attributed to Chapot-Chartier, M.-P..

6 recordsLinked to original sources

bioRxiv2024

The L,D-transpeptidation pathway is inhibited by antibiotics of the β-lactam class in Clostridioides difficile

The resistance of Clostridioides difficile to the {beta}-lactam antibiotics cephalosporins, which target the peptidoglycan (PG) assembly, is a leading contributor to the development of C. difficile infections. C. difficile has an original PG structure with a predominance of 3[->]3 cross-links generated by L,D-transpeptidases (LDTs). C. difficile forms spores and we show that the spore cortex PG contains exclusively 3[->]3 cross-links. PG and spore cortex of C. difficile cells were largely unaffected by the deletion of the three predicted LDTs, revealing the implication of a new family of LDTS. The D,D-carboxypeptidases producing the essential LDT substrate were inactivated by cephalosporins, resulting in the inhibition of the L,D-transpeptidation pathway. In contrast, the participation of penicillin-binding proteins (PBPs) to PG cross-linking increased in the presence of the antibiotics. Our findings highlight that cephalosporin resistance is not primarily mediated by LDTs and illustrate the plasticity of the PG biosynthesis machinery in C. difficile.

microbiology↗

bioRxiv2023

Diving into bacterial dormancy: emergence of osmotically stable wall-less forms in an aquatic environment

Bacteria can respond to environmental stresses by entering a dormant state, called viable but non-culturable (VBNC) state, in which they no longer grow in routine culture media. VBNC pathogens pose thus a significant risk for human and animal health as they are not detected by standard growth-based techniques and can "wake up" back into a vegetative and virulent state. Although hundreds of species were reported to become VBNC in response to different stresses, the molecular mechanisms governing this phenotypic switch remain largely elusive. Here, we characterized the VBNC state transition process in the Gram-positive pathogen Listeria monocytogenes in response to nutritional deprivation. By combining fluorescence microscopy, cryo-electron tomography and analytical biochemistry, we found that starvation in mineral water drives L. monocytogenes into a VBNC state via a mechanism of cell wall (CW) shedding that generates osmotically stable CW-deficient (CWD) coccoid forms. This phenomenon occurs in multiple L. monocytogenes strains and in other Listeria species, suggesting it may be a stress-adapting process transversal to the Listeria genus. Transcriptomic and gene-targeted approaches revealed the stress response regulator SigB and the autolysin NamA as major moderators of CW loss and VBNC state transition. Finally, we show that this CWD dormant state is transient as VBNC Listeria revert back to a walled, vegetative and virulent state after passage in embryonated eggs. Our findings provide unprecedented detail on the mechanisms governing the transition to a VBNC state, and reveal that dormant CWD bacterial forms can naturally arise in aquatic environments without osmotic stabilization. This may represent an alternative strategy for bacterial survival in oligotrophic conditions, which can potentially generate public health-threatening reservoirs of undetectable pathogens.

microbiology↗

bioRxiv2022

Structure-Function analysis of Lactiplantibacillus plantarum DltE reveals D-alanylated lipoteichoic acids as direct symbiotic cues supporting Drosophila juvenile growth

Metazoans establish mutually beneficial interactions with their resident microorganisms. However, our understanding of the microbial cues contributing to host physiology remains elusive. Previously, we identified a bacterial machinery encoded by the dlt operon involved in Drosophila melanogasters juvenile growth promotion by Lactiplantibacillus plantarum. Here, using crystallography combined with biochemical and cellular approaches, we investigate the physiological role of an uncharacterized protein (DltE) encoded by this operon. We show that LTAs but not WTAs are D-alanylated in Lactiplantibacillus plantarumNC8 cell envelope and demonstrate that DltE is a D-Ala carboxyesterase removing D-Ala from LTA. Using the mutualistic association of L. plantarumNC8 and Drosophila melanogaster as a symbiosis model, we establish that D-Ala-LTAs are direct symbiotic cues supporting intestinal peptidase expression and juvenile growth in Drosophila. Our results pave the way to probing the contribution of D-Ala-LTA to host physiology in other symbiotic models.

microbiology↗

bioRxiv2020

Ser/Thr kinase-dependent phosphorylation of the peptidoglycan hydrolase CwlA controls its export and modulates cell division in Clostridioides difficile

Cell growth and division require a balance between synthesis and hydrolysis of the peptidoglycan (PG). Inhibition of PG synthesis or uncontrolled PG hydrolysis can be lethal for the cells, making it imperative to control peptidoglycan hydrolase (PGH) activity. The serine/threonine kinases (STKs) of the Hanks family control cell division and envelope homeostasis, but only a few kinase substrates and associated molecular mechanisms have been identified. In this work, we identified CwlA as the first STK-PrkC substrate in the human pathogen Clostridiodes difficile and showed that CwlA is an endopeptidase involved in daughter cell separation. We demonstrated that PrkC-dependent phosphorylation inhibits CwlA export, therefore controlling the hydrolytic activity in the cell wall. High level of CwlA at the cell surface led to cell elongation, whereas low level caused cell separation defects. We thus provided evidence that the STK signaling pathway regulates PGH homeostasis to precisely control PG hydrolysis during cell division.

microbiology↗

bioRxiv2019

D-alanylation of Teichoic Acids in Bacilli impedes the immune sensing of peptidoglycan in Drosophila

Modification of cell wall components is a prominent mean for pathogens to hinder host immune defenses. Here, using the Drosophila model, we aimed at characterizing the role of D-alanine esterification of teichoic acids (TAs) in the resistance of Bacillus thuringiensis to host defenses in vivo. We show that, by preventing cationic antimicrobial effectors-mediated bacterial lysis, this cell wall modification also limits the release of peptidoglycan immunostimulatory fragments thus impeding their sensing and the subsequent induction of the IMD- NF-{kappa}B pathway. Interestingly, we show that this strategy is also adopted by Lactobacillus plantarum, a bona fide commensal, to fine-tune its immunomodulatory potential in the Drosophila gut. Markedly, we show that the D-alanylation of TAs is essential for the resistance of L. plantarum to gut lysozyme. Altogether our data shed light on the mechanism underlying the persistence and the low immunostimulatory potential of L. plantarum in the Drosophila gut.

immunology↗

bioRxiv2017

D-Alanine esterification of teichoic acids contributes to Lactobacillus plantarum mediated intestinal peptidase expression and Drosophila growth promotion upon chronic undernutrition

The microbial environment influence animal physiology. However, the underlying molecular mechanisms of such functional interactions are largely undefined. Previously, we showed that upon chronic undernutrition, strains of Lactobacillus plantarum, a dominant commensal partner of Drosophila, promote host juvenile growth and maturation partly via enhanced expression of intestinal peptidases. By screening a transposon insertion library of Lactobacillus plantarum in gnotobiotic Drosophila larvae, we identify a bacterial cell wall modifying machinery encoded by the pbpX2-dltXABCD operon that is critical to enhance host digestive capabilities and promote growth and maturation. Deletion of this operon leads to bacterial cell wall alteration with a complete loss of teichoic acids D-alanylation. We thus conclude that teichoic acids modifications participate in commensal-host interactions and specifically, D-alanine esterification of teichoic acids contributes to optimal L. plantarum mediated intestinal peptidase expression and Drosophila juvenile growth upon chronic undernutrition.\n\nHighlights- LpNC8 mutant library screening identifies genes affecting Drosophila growth promotion.\n- pbpX2-dlt operon is required for D-alanylation of teichoic acids and Drosophila growth.\n- Deleting the pbpX2-dlt operon alters host intestinal peptidase expression.\n- Peptidoglycan and pbpX2-dlt dependent signals are required for LpNC8 mediated growth promotion.\n\n\neTOC blurbAnimals establish interactions with their microbial communities that shape many aspects of their physiology including juvenile growth. However, the underlying molecular mechanisms are largely undefined. Matos et al. reveal that bacterial teichoic acids modifications contribute to host juvenile growth promotion.

microbiology↗