Biology subjects

Grognot, M.

Publications and source records attributed to Grognot, M..

5 recordsLinked to original sources

bioRxiv2026

Swimming motility in the gut microbiota is diverse and increased in inflammation.

Swimming motility has long been studied as a virulence mechanism of enteric pathogens, while the resident microbiota's motility has only been inferred from proxies or explored through a few model species. This study presents a direct, functional analysis of gut bacterial motility in health and inflammation. Using phase-contrast microscopy and high-throughput 3D tracking, we quantified motile bacteria and characterized their swimming behaviours directly in diluted fresh gut content. In healthy mice, fewer than 3% of bacteria were motile along the digestive tract, and their swimming patterns were dominated not by the run-tumble behavior of model gut species but by diverse behaviours rich in reverses. In five mouse models with intestinal inflammation (spanning chemical, genetic, dietary and infectious etiologies) the motile fraction rose by at least 4-fold, correlating with elevated Lipocalin-2 where measured. Reverse-rich patterns remained prevalent in these inflamed conditions, with the notable exception of Salmonella infection. Paired metagenomics and metatranscriptomics showed enrichment of flagellar genes, while communities transferred into cecal water from inflamed mice raised their motile fraction within an hour, indicating that the rise reflects both enrichment of motile taxa and rapid modulation within existing populations. In vitro assays with human-derived isolates confirmed motility across several phyla, with variability down to strain level, and identified oxygen and viscosity as key modulators. These findings support increased motility as a hallmark of the inflamed gut and challenge established assumptions about gut bacterial motility.

microbiology↗

bioRxiv2026

Cell-body curvature modulates stall frequency to enhance Vibrio cholerae swimming and chemotaxis through hydrogels

The swimming motility of Vibrio cholerae is a virulence factor that aids in breaching the mucus layer of the small intestine. V. cholerae cells have a curved cell shape and previous work demonstrated that loss of curvature decreases infectivity. Here we investigate the mechanism by which V. choleraes curvature affects single-cell motility within mucus-mimicking environments. Using a multiscale chemotaxis assay, we compared the chemotactic performance of wild-type curved cells (O1 El Tor C6706) and straight mutants under linear chemical gradients in liquid solutions, viscous solutions, and soft agar hydrogels. Our findings reveal that curved and straight V. cholerae exhibit similar swimming properties in liquid and purely viscous solutions but significantly differ in hydrogels, with curved cells demonstrating an 86% increase in average chemotactic drift compared to straight mutants in the same chemical gradients. Trajectory analysis indicates that swimming speeds are comparable, but straight mutants experience more frequent stalls, reducing the total time spent swimming. We also found that stalls further reduce chemotactic performances by imposing an average reorientation of bacteria down the chemical gradient, regardless of cell shape. In-silico coarse-grained molecular dynamics simulations corroborate these results and extend them over the wide range of intestinal mucus hydrogel stiffnesses. This model also identifies an optimal curvature for enhanced movement through hydrogel-like meshes that is close to the real median curvature of the pathogen. Our findings thus highlight the mechanisms underpinning cell shapes role in V. choleraes pathogenicity and underscore the necessity of studying bacterial behaviors under conditions that simulate host environments.

microbiology↗

bioRxiv2023

Physiological adaptation in flagellar architecture improves Vibrio alginolyticus chemotaxis in complex environments

Bacteria navigate natural habitats with a wide range of mechanical properties, from the ocean to the digestive tract and soil, by rotating helical flagella like propellers. Species differ in the number, position, and shape of their flagella, but the adaptive value of these flagellar architectures is unclear. Many species traverse multiple types of environments, such as pathogens inside and outside a host. We investigate the hypothesis that flagellar architectures mediate environment-specific benefits in the marine pathogen Vibrio alginolyticus which exhibits physiological adaptation to the mechanical environment. In addition to its single polar flagellum, the bacterium produces lateral flagella in environments that differ mechanically from water. These are known to facilitate surface motility and attachment. We use high-throughput 3D bacterial tracking to quantify chemotactic performance of both flagellar architectures in three archetypes of mechanical environments relevant to the bacteriums native habitats: water, polymer solutions, and hydrogels. We reveal that lateral flagella impede chemotaxis in water by lowering the swimming speed but improve chemotaxis in both types of complex environments. Statistical trajectory analysis reveals two distinct underlying behavioral mechanisms: In viscous solutions of the polymer PVP K90, lateral flagella increase the swimming speed. In agar hydrogels, despite lowering the swimming speed, lateral flagella improve overall chemotactic performance by preventing trapping in pores. Our findings show that lateral flagella are multi-purpose tools with a wide range of applications beyond surfaces. They implicate flagellar architecture as a mediator of environment-specific benefits and point to a rich space of bacterial navigation behaviors in complex environments.

microbiology↗

bioRxiv2021

Vibrio cholerae motility in aquatic and mucus-mimicking environments

Cholera disease is caused by Vibrio cholerae infecting the lining of the small intestine and results in severe diarrhea. V. choleraes swimming motility is known to play a crucial role in pathogenicity and may aid the bacteria in crossing the intestinal mucus barrier to reach sites of infection, but the exact mechanisms are unknown. The cell can be either pushed or pulled by its single polar flagellum, but there is no consensus on the resulting repertoire of motility behaviors. We use high-throughput 3D bacterial tracking to observe V. cholerae swimming in buffer, in viscous solutions of the synthetic polymer PVP, and in mucin solutions that may mimic the host environment. We perform a statistical characterization of its motility behavior on the basis of large 3D trajectory datasets. We find that V. cholerae performs asymmetric run-reverse-flick motility, consisting of a sequence of a forward run, reversal, and a shorter backward run, followed by a turn by approximately 90{degrees}, called a flick, preceding the next forward run. Unlike many run-reverse-flick swimmers, V. choleraes backward runs are much shorter than its forward runs, resulting in an increased effective diffusivity. We also find that the swimming speed is not constant, but subject to frequent decreases. The turning frequency in mucin matches that observed in buffer. Run-reverse-flick motility and speed fluctuations are present in all environments studied, suggesting that these behaviors may also occur in natural aquatic habitats as well as the host environment. ImportanceCholera disease produces vomiting and severe diarrhea and causes approximately 100,000 deaths per year worldwide. The disease is caused by the bacterium Vibrio cholerae colonizing the lining of the small intestine. V. choleraes ability to swim is known to increase its infectivity, but the underlying mechanisms are not known. One possibility is that swimming may aid in crossing the protective mucus barrier that covers the lining of the small intestine. Our work characterizing how V. cholerae swims in environments that mimic properties of the host environment may advance the understanding of how motility contributes to infection.

microbiology↗

bioRxiv2020

A multiscale 3D chemotaxis assay reveals bacterial navigation mechanisms

How bacteria navigate environmental chemical gradients has implications ranging from health to climate science. The underlying behavioral mechanisms are unknown for most species due to a lack in techniques bridging scales from individual 3D motility behavior to the statistical power required to assess the resulting performance. We present the first demonstration of such a multiscale 3D chemotaxis assay and reveal that Caulobacter crescentus chemotaxis breaks with the Escherichia coli paradigm.

microbiology↗