Biology subjects

Leguillier, V.

Publications and source records attributed to Leguillier, V..

4 recordsLinked to original sources

bioRxiv2026

The fatty acid synthesis pathway is a checkpoint for lipoteichoic acid synthesis in Staphylococcus aureus

Bacterial membranes comprise diverse lipids whose proportions vary according to environmental conditions. How cells direct lipid flux toward specific products remains unclear. We address this question in the human pathogen Staphylococcus aureus, where multiple lipid products compete for a common precursor, the major phospholipid, phosphatidylglycerol (PG). One product, lipoteichoic acid (LTA), is essential for cell division, envelope homeostasis, and virulence. Lipids and metabolites were quantified to identify factors that prioritize LTA synthesis over the other PG-derived products. We identify upstream fatty acid synthesis (FASII) pathway as a key control point for LTA production. Inhibition of FASII by antibiotics or gene inactivation causes LTA depletion. FASII inhibition similarly affects LTA in Streptococcus agalactiae, suggesting conservation of this LTA control strategy. Changes in membrane fatty acids do not account for LTA depletion. Instead, we show that FASII inhibition causes a drop in intracellular glycerophosphate (GroP), a precursor for both PG and LTA. Under these conditions of GroP limitation, PG flux favors production of a non-GroP lipid, cardiolipin. Moreover, combined inhibition of FASII and WTA blocks S. aureus growth, confirming the lethality of depleting LTA and WTA simultaneously. This study resolves how S. aureus manages phospholipid flux, by prioritizing the synthesis of GroP-rich LTA or of non-GroP-containing lipids according to FASII-controlled GroP availability.

microbiology↗

bioRxiv2025

Biotope-dependent High Level Resistance to Reactive Oxygen Species, Antibiotic Tolerance, and Virulence of Staphylococcus aureus

The human and livestock pathogen Staphylococcus aureus poses a major clinical challenge due to antibiotic treatment failure. Its resilience is mainly attributed to antibiotic resistance and tolerance mechanisms related to persistence. Here we investigate how two infection-relevant biotopes, milk and serum, shape S. aureus pathogenic properties and capacity to withstand environmental stresses. Milk-versus serum-adapted bacteria show gross differences in envelope physical properties, membrane fatty acid composition and rigidity, and pigment production, and display distinct proteomic profiles. Compared to serum, milk adaptation of S. aureus confers extreme resistance to ROS damage, pronounced antimicrobial tolerance, and accelerated killing in an insect infection model. High level S. aureus pigmentation in whole milk is stimulated by milk lipids, and is responsible for high ROS resistance. The remarkable robustness of S. aureus in a milk biotope may signal the need to adjust antibiotic regimens when treating mastitis infections in humans and livestock.

microbiology↗

bioRxiv2024

Metabolic rerouting by gain-of-function mutations overcomes plsX essentiality in Staphylococcus aureus

Phospholipids are essential components of most cell membranes. In Staphylococcus aureus, PlsX acyltransferase is considered indispensable for initiating phospholipid synthesis, unless exogenous fatty acids (FAs) are available to bypass this requirement. We report that S. aureus can capture internal FA sources to overcome PlsX essentiality in a {Delta}plsX mutant via point mutations in either of two genes: fabF, which encodes the FA synthesis enzyme 3-oxoacyl-(acyl-carrier-protein) synthase II, or fadM, which encodes an understudied bifunctional acyl-CoA thioesterase and ACP binding protein. Despite growth rescue, both {Delta}plsX suppressors differ from the parental strain by producing phospholipids with shortened FA lengths suggesting that both suppressors lead to premature FA release during synthesis. Additionally, both suppressors display increased sensitivity to {beta}-lactam antibiotics. The similar behavior of both suppressors led us to show that fabF suppressors require the presence of fadM, indicative of FabF-FadM cooperation. We propose that reduced processivity of FabF suppressor variants, or greater availability of FadM for ACP binding in FadM variants, facilitates FA release from FabF-acyl-ACP intermediates. A FabF-FadM relay leading to FA release may contribute to homeostasis between FASII and phospholipid synthesis pathways. SignificancePhospholipids are vital cell membrane components. The essential Staphylococcus aureus phospholipid synthesis enzyme PlsX uses acyl-ACP, the end-product of fatty acid (FA) synthesis (FASII), to initiate phospholipid production. Despite its central role, PlsX can be substituted by exogenous FAs whose phosphorylation yields the same product. We discovered that without FA supplementation, mutants arise that rescue growth, indicating that internal FAs are released. Mutations occurred in either FabF, a FASII enzyme, or in FadM, an incompletely characterized protein. Our analyses give evidence that FabF and FadM proteins cooperate, and facilitate FA availability when either protein is mutated. We propose that in normal conditions, FadM might act as an "overflow valve" by releasing FAs from the FabF intermediate, which prevents buildup of FASII intermediates, and ensures FA-phospholipid balance. Remarkably, while this pathway rescues S. aureus growth, it sensitizes the MRSA strain to {beta}-lactam antibiotics.

microbiology↗

bioRxiv2022

Low-cost gold-leaf electrode as a platform for Escherichia coli immuno-detection

Gold electrodes are one of most prevalent substrates in electrochemical biosensors because they can be easily and highly efficiently functionalized with thiolated biomolecules. However, conventional methods to fabricate gold electrodes are costly, time consuming and require onerous equipment. Here, an affordable method for rapid fabrication of an electrochemical immune-sensor for Escherichia coli detection is presented. The gold electrode was generated using 24-karat gold leaves and low-cost polyvinyl chloride adhesive sheets covered with an insulating PTFE layer. The gold-leaf electrode (GLE) was patterned using laser ablation and characterized by cyclic voltammetry, electrochemical impedance spectroscopy, scanning electronic microscopy, contact angle and 3D profiling. The GLEs were modified by a self-assembled mercaptopropionic monolayer, followed by surface activation to allow binding of the specific anti-E. coli antibody via carbodiimide linking. The biosensor showed a detection limit of 2 CFU/ml and a linear dynamic range of 10 - 107 CFU/ml for E. coli cells. No false positive signals were obtained from control bacteria. The obtained results demonstrated suitability of GLE for use in biosensors with high reliability and reproducibility. It is foreseeable that our work will inspire design of point-of-need biosensors broadly applicable in low-resource settings.

microbiology↗