Biology subjects

Lecher, S.

Publications and source records attributed to Lecher, S..

4 recordsLinked to original sources

bioRxiv2026

Nasal environment potentiates the pathogenicity of Bordetella pertussis

Pertussis remains a major health concern, as acellular vaccines fail to prevent nasal infection and transmission. The nasal cavity is the primary niche for Bordetella pertussis colonization, but how this particular environment shapes bacterial pathogenicity remains poorly understood. Here we developed bacterial culture conditions that replicate the nasal environment, combining nasal-fluid-like transition metals concentrations with nasal cavity temperature. Using complementary transcriptomic and proteomic approaches, Dual RNA-sequencing, and in vitro and in vivo infection models, we assessed their impact on host-pathogen interactions. Nasal-like conditions reprogram B. pertussis into a state of increased virulence, conferring functional advantages for efficient bacterium-cell interactions and inducing physiological remodeling of human nasal epithelial cells. Finally, we showed that nasal preconditioning promotes efficient early B. pertussis colonization in mice. Altogether, these findings identify the nasal cavity as an instructive niche priming B. pertussis for efficient upper respiratory tract colonization following airborne transmission.

microbiology↗

bioRxiv2026

The cytoplasmic C-terminal domain of the MmpL11 lipid transporter is required for interaction with its co-cistronic partner MSMEG_0240 in Mycobacterium smegmatis

MmpL proteins play an important role in the various mechanisms associated with mycobacterial virulence. Identification of interacting protein partners by classical in vitro methods is hampered by the low solubility of these integral membrane proteins. In this study, we used two independent biotin proximity labelling assays (APEX2 and BioID) to define the proxisome of MmpL11 in Mycobacterium smegmatis. Crucially, these techniques are performed directly in the organism of interest, allowing the detection of potentially transient or weak interactions in multiprotein complexes and preserving the subcellular structures and the presence of cofactors or post-translational modifications that can also impact protein-protein interactions. BioID leads to the biotinylation of lysine residues, whereas APEX2 leads to the biotinylation of mainly tyrosine residues; they have also been shown to have different effective labelling radii. On one hand, an interaction was detected between the cytoplasmic C-terminal domain of MmpL11 and MSMEG_0240, a protein of unknown function, using BioID. This interaction was confirmed using both MmpL11 and MSMEG_0240 as fusions with BirA and was further supported by AlphaFold3 prediction. On the other hand, APEX2 did not detect proximity between MmpL11 and MSMEG_0240, probably due to the absence of accessible tyrosines. However, both approaches identified MSMEG_0940 as an additional interactant with MmpL11 that also depends on its C-terminal domain. Overall, this study demonstrates the utility of APEX2 and BioID as complementary tools for defining the proxisome of mycobacterial proteins.

microbiology↗

bioRxiv2025

Exploiting Vitamin B6 Dependency: BVL3572S Inhibits HisC and AlaA to Kill Mycobacterium tuberculosis

Tuberculosis remains the leading cause of death from a single infectious agent worldwide, and the growing prevalence of multi-drug resistant Mycobacterium tuberculosis (Mtb) underscores the urgent need for antibiotics with novel mechanisms of action. Here, we characterize BVL3572S, a hydroxamic acid-containing compound that is bactericidal and potently inhibits the growth of both extracellular and intracellular Mtb. Integrated transcriptomic, genetic, and biochemical analyses identified the pyridoxal phosphate (PLP)-dependent aminotransferases HisC (Rv1600) and AlaA (Rv0337c; formerly AspC) as the primary molecular targets of BVL3572S, thereby simultaneously impacting L-histidine and L-alanine biosynthesis. Spontaneous resistance mutants harbored mutations in hisC or alaA. Target engagement was further supported by overexpression studies: AlaA overexpression increased resistance in the presence of L-His whereas HisC overexpression paradoxically increased susceptibility. X-ray crystallography revealed a covalent adduct between PLP and BVL3572S within the HisC active site. The short occupancy of this adduct suggests a futile cycle that sequesters PLP. Isotopic labeling revealed widespread perturbation of amino acid biosynthesis, consistent with PLP starvation. The stepwise resistance observed upon supplementation with L-His and L-Ala together or with PLP alone suggests inhibition of multiple targets. Genome-scale CRISPRi and Tn-seq analyses additionally indicated disruptions in central metabolism, cell envelope integrity, and redox balance, possibly due to PLP depletion cascades. Consistent with its inhibition of AlaA, BVL3572S displayed strong synergy with D-cycloserine, a second-line antitubercular drug targeting D-alanine synthesis and impacting peptidoglycan synthesis, highlighting the potential of this compound in combination therapy. Collectively, our findings establish BVL3572S as a promising lead compound acting through a previously unexploited, multitarget mechanism that induces broad metabolic stress in Mtb, offering a novel therapeutic strategy against drug-resistant tuberculosis.

microbiology↗

bioRxiv2021

Large-scale conformational changes of FhaC provide insights into the two-partner secretion mechanism

The Two-Partner secretion pathway mediates protein transport across the outer membrane of Gram-negative bacteria. TpsB transporters belong to the Omp85 superfamily, whose members catalyze protein insertion into, or translocation across membranes without external energy sources. They are composed of a transmembrane {beta} barrel preceded by two periplasmic POTRA domains that bind the incoming protein substrate. Here we used an integrative approach combining in vivo assays, mass spectrometry, nuclear magnetic resonance and electron paramagnetic resonance techniques suitable to detect minor states in heterogeneous populations, to explore transient conformers of the TpsB transporter FhaC. This revealed substantial, spontaneous conformational changes with a portion of the POTRA2 domain coming close to the lipid bilayer and surface loops. Specifically, the amphipathic {beta} hairpin immediately preceding the first barrel strand can insert into the {beta} barrel. We propose that these motions enlarge the channel and hoist the substrate into it for secretion. An anchor region at the interface of the {beta} barrel and the POTRA2 domain stabilizes the transporter in the course of secretion. Our data propose a solution to the conundrum how these transporters mediate protein secretion without the need for cofactors, by utilizing intrinsic protein dynamics.

biophysics↗