Biology subjects

Solgadi, A.

Publications and source records attributed to Solgadi, A..

5 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↗

bioRxiv2026

Versatility of Campylobacter jejuni Bf extracellular vesicles in regulating adaptation and virulence under combined thermal and oxidative stress

The high prevalence of aerotolerant human Campylobacter jejuni isolates suggests a correlation between the ability to survive in aerobic conditions, virulence and resistance to harsh stress conditions. However, the mechanisms are still unclear. Here, we investigated the role of bacterial extracellular vesicles (bEVs) in the adaptation of the clinical aerotolerant C. jejuni Bf strain to thermal and oxidative stress. We show that C. jejuni Bf survives and actively multiplies under this combined stress. Stress exposure induced cell rounding and loss of motility, remodeling of membrane composition, decreased membrane fluidity, and metabolic reprogramming with increased intracellular ATP levels. Lipidomic analyses further revealed that bEVs composition is markedly different from that of the parent membranes indicating that vesicle formation is selective and regulated. Although bEVs were produced in similar amounts under both microaerophilic and stress conditions, stress exposure generated significantly larger vesicles with greater diameter and dry mass, and altered their protein and lipid profiles. bEVs derived from stressed cells showed increased toxicity toward the epithelial barrier of Caco-2 cells. Taken together, these results indicate that C. jejuni bEV secretion is part of a survival strategy that connects environmental adaptation with pathogenicity. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=80 SRC="FIGDIR/small/714464v1_ufig1.gif" ALT="Figure 1"> View larger version (16K): org.highwire.dtl.DTLVardef@17aa2aforg.highwire.dtl.DTLVardef@4eab9dorg.highwire.dtl.DTLVardef@e4fba8org.highwire.dtl.DTLVardef@146109a_HPS_FORMAT_FIGEXP M_FIG C_FIG

microbiology↗

bioRxiv2023

The double-edged role of FASII regulator FabT in Streptococcus pyogenes infection

In Streptococcus pyogenes, the type II fatty acid (FA) synthesis pathway FASII is feedback- controlled by the FabT repressor bound to an acyl-Acyl carrier protein. Despite FabT defects being linked to reduced virulence in animal models, spontaneous fabT mutants arise in vivo. To resolve this paradox, we characterized the conditions and mechanisms that require FabT activity, and those that promote fabT mutant emergence. The primary fabT mutant defect is energy dissipation: specific nutrients are consumed, but the mutant fails to grow on human tissue, cells, or cell filtrates where nutrients are limited. These features explain the FabT requirement during infection. Conversely, fabT mutants exhibited a marked growth advantage over the wild-type in biotopes rich in saturated FAs. fabT mutants emerge in this context, where continued FASII activity prevented environmental FA incorporation. An ex vivo muscle model demonstrated that wild-type S. pyogenes was inhibited, while fabT mutant growth was stimulated, but conditional to FASII activity. Our findings elucidate the rationale for emerging fabT mutants that improve survival in lipid-rich biotopes, but lead to a genetic impasse for infection.

microbiology↗

bioRxiv2019

Alteration of cardiolipin-dependent mitochondrial coupling in muscle protects against obesity

The tubular shape of mitochondrial cristae depends upon a specific composition of the inner mitochondrial membrane, including cardiolipin that allows strong curvature and promotes optimal organization of ATP synthase. Here we identify Hacd1, which encodes an enzyme involved in very long chain fatty acid biosynthesis, as a key regulator of composition, structure and functional properties of mitochondrial membranes in muscle. In Hacd1-deficient mice, the reduced cardiolipin content was associated with dilation of cristae and caused defective phosphorylating respiration, characterized by absence of proton leak and oxidative stress.\n\nThe skeletal muscle-specific mitochondrial coupling defect produced a global elevation in basal energy expenditure with increased carbohydrate and lipid catabolism, despite decreased muscle mass and locomotor capacities. Mice were protected against diet-induced obesity despite reduced muscle activity, providing an in vivo proof of concept that reducing mitochondrial coupling efficiency in skeletal muscle might be an actionable mechanism in metabolic disease conditions.

cell biology↗

bioRxiv2019

Permissive Fatty Acid Incorporation in Host Environments Promotes Staphylococcal Adaptation to FASII Antibiotics

Development of fatty acid synthesis pathway (FASII) inhibitors against the major human pathogen Staphylococcus aureus hinges on the accepted but unproven postulate that an endogenously synthesized branched chain fatty acid is required to complete membrane phospholipids. Evidence for anti-FASII efficacy in animal models supported this view. However, restricted test conditions used previously to show FASII antibiotic efficacy led us to investigate these questions in a broader, host-relevant context. We report that S. aureus rapidly adapts to FASII antibiotics without FASII mutations when exposed to host environments. Treatment with a lead FASII antibiotic upon signs of infection, rather than just after inoculation as commonly practiced, failed to eliminate S. aureus from infected organs in a septicemia model. In vitro, addition of serum facilitated rapid S. aureus FASII bypass by environmental fatty acid (eFA) replacement in phospholipids. Serum lowers membrane stress, leading to increased retention of the two substrates required for exogenous fatty acid (eFA) utilization. In these conditions, eFA occupy both phospholipid positions 1 and 2, regardless of anti-FASII selection. This study revises conclusions on S. aureus fatty acid requirements by disproving the postulate of fatty acid stringency, and reveals an Achilles heel for using FASII antibiotics to treat infection in monotherapy.\n\nSignificance statementAntibiotic discovery to overcome treatment failure has huge socio-medical and economic stakes. The fatty acid synthesis (FASII) pathway is considered an ideal druggable target against the human pathogen Staphylococcus aureus, based on evidence of anti-FASII efficacy in infection models, and the postulate that S. aureus synthesizes an irreplaceable fatty acid. We report that S. aureus alters its behavior in host-relevant conditions. Administering FASII antibiotics upon signs of infection, rather than just after inoculation as frequently practiced, failed to clear septicemic infections. In serum, S. aureus rapidly overcomes FASII antibiotics by incorporating alternative fatty acids. We conclude that previously, premature antibiotic treatments and experimental constraints masked S. aureus antibiotic adaptation capacity. These findings should help streamline future drug development programs.

microbiology↗