Biology subjects

Le Gall, A.

Publications and source records attributed to Le Gall, A..

4 recordsLinked to original sources

bioRxiv2025

Tunable simultaneous propulsion by two distinct motility motors drives surface motility in bacteria

Motility allows cells to explore their surroundings, evade threats, and coordinate collective behaviors. Many organisms, from bacteria to animals, encode more than one motility system, yet whether and how mechanistically distinct systems are integrated within individual cells remains largely unresolved. We address this question in the predatory bacterium Myxococcus xanthus, which navigates surfaces using two mechanistically and evolutionarily distinct motors: focal-adhesion-based gliding and type IV pili-driven twitching. For this, we develop an imaging-based quantitative behavioral phenotyping method to show that both motors are simultaneously active within individual cells and jointly power cell movement. Cells engaging both motors move faster and explore space more effectively than cells using either motor alone, expanding locomotion performance. Extracellular calcium tunes their relative contributions, progressively shifting cells from gliding- to twitching-dominated propulsion. Unexpectedly, the gliding motor can boost twitching even without anchoring to the surface, revealing that cooperation between motility systems extends beyond simultaneous force generation. Together, these findings reveal that evolutionarily distinct motility systems can function as components of a single, environmentally tunable propulsion strategy.

microbiology↗

bioRxiv2020

MiSiC, a general deep learning-based method for the high-throughput cell segmentation of complex bacterial communities

Studies of microbial communities by live imaging require new tools for the robust identification of bacterial cells in dense and often inter-species populations, sometimes over very large scales. Here, we developed MiSiC, a general deep-learning-based segmentation method that automatically segments a wide range of spatially structured bacterial communities with very little parameter adjustment, independent of the imaging modality. Using a bacterial predator-prey interaction model, we demonstrate that MiSiC enables the analysis of interspecies interactions, resolving processes at subcellular scales and discriminating between species in millimeter size datasets. The simple implementation of MiSiC and the relatively low need in computing power make its use broadly accessible to fields interested in bacterial interactions and cell biology.

microbiology↗

bioRxiv2019

ATP-driven separation of liquid phase condensates in bacteria

Liquid-liquid phase separated (LLPS) states are key to compartmentalise components in the absence of membranes, however it is unclear whether LLPS condensates are actively and specifically organized in the sub-cellular space and by which mechanisms. Here, we address this question by focusing on the ParABS DNA segregation system, composed of a centromeric-like sequence (parS), a DNA-binding protein (ParB) and a motor (ParA). We show that parS-ParB associate to form nanometer-sized, round condensates. ParB molecules diffuse rapidly within the nucleoid volume, but display confined motions when trapped inside ParB condensates. Single ParB molecules are able to rapidly diffuse between different condensates, and nucleation is strongly favoured by parS. Notably, the ParA motor is required to prevent the fusion of ParB condensates. These results describe a novel active mechanism that splits, segregates and localises non-canonical LLPS condensates in the sub-cellular space.

cell biology↗

bioRxiv2018

HIV-1 specifically traps and depletes CD9 and CD81 tetraspanins during egress

HIV-1 assembly specifically alters both partitioning and dynamics of the tetraspanins CD9 and CD81 forming enriched areas where the virus buds. Importantly the presence of these proteins at exit sites and in viral particles inhibits virus-induced membrane fusion. To get molecular insights into tetraspanins partitioning in this viral context, we correlated nanoscale CD9 mapping obtained by super resolution microscopy to membrane topography probed by Atomic Force Microscopy (AFM). We demonstrated that CD9 is specifically trapped within the nascent viral particles, especially at buds tips, and that Gag mediate CD9 and CD81 depletion from cellular surfaces, even in the absence of Vpu and Nef, resulting from tetraspanins escaping from the plasma membrane during HIV-1 release. In addition, we showed that CD9 is organized as small membrane assemblies of few tens of nanometers that can coalesce upon Gag expression. Our results support a functional redundancy among tetraspanins during HIV release.

microbiology↗