Biology subjects

Bouchard, A.

Publications and source records attributed to Bouchard, A..

3 recordsLinked to original sources

bioRxiv2026

Methods for evaluating bacterial dispersal on hyphal networks

In heterogeneous environments, the hyphae of filamentous fungi and oomycetes can facilitate the dispersal of other microorganisms. The use of these "fungal highways" (FH) is regulated by both physical and biological factors with their interplay resulting in variable capabilities of different microbes to establish FH. Several devices have been developed to test the movement of bacteria across mycelium. However, these methods are usually time-consuming and cannot be applied either at a large scale or in a high throughput format. In this study, we developed 3D-printed experimental devices that physically separate two environments while allowing hyphal networks to act as bridges for bacterial movement. The final design allows for the simultaneous testing of up to 10 pairs and the inclusion of any culturing media. With these devices, we investigated how fungal-bacterial pairing, nutrient conditions, and inoculation strategies influence FH formation. Bacterial transport was limited in nutrient-rich media but increased under poorer nutrient conditions, consistent with enhanced exploratory growth of the mycelium. Both cis- and trans-inoculation supported FH formation, although bacterial arrival was delayed in the absence of co-inoculation. The devices were used to demonstrate that transport of bacteria by FH was relevant for the colonization of a natural substrate. Finally, we established a novel in planta assay to evaluate FH formation during host colonization. This assay demonstrated that Fusarium graminearum can transport bacteria during wheat spike colonization. Together, these results provide accessible, scalable tools to study hyphal-mediated bacterial dispersal and highlight the combined role of biological specificity and nutrient context in the establishment of FH. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=75 SRC="FIGDIR/small/719220v1_ufig1.gif" ALT="Figure 1"> View larger version (25K): org.highwire.dtl.DTLVardef@1cf39aforg.highwire.dtl.DTLVardef@1d41e6corg.highwire.dtl.DTLVardef@1196637org.highwire.dtl.DTLVardef@85cc6c_HPS_FORMAT_FIGEXP M_FIG C_FIG

microbiology↗

bioRxiv2025

Fighting Aspergillus infection using biocontrol bacteria: A proof-of-concept of environmental interference in a translational setting

Aspergillus fungi are opportunistic pathogens that affect millions of people worldwide. Aspergilli produce organic acids to optimize the environmental pH and match the needs of their enzymatic machinery. In this study, we tested the hypothesis that this also occurs during infection. By producing oxalic acid (OA), Aspergillus would manipulate pH during lung infection and thus, interfering with this process could control the pathogen. To test this hypothesis, we assessed in silico the potential for OA production in a wide range of Aspergilli. A genetic marker for AO production was detected in most of the species including prevalent human pathogens. We tested OA production in vitro in four strains of A. niger and A. fumigatus, but only one of the A. niger strains produced OA consistently. For this fungal strain, oxalotrophic bacteria were able to control fungal growth via OA consumption. To translate this observation into a pre-clinical system, increasingly complex experiments were performed. In 3D-cell cultures, A. niger also secreted OA and modified pH and free Ca2+. Co-inoculation of the oxalotrophic bacterium inhibited the development of the fungus. However, biocontrol could not be replicated in Galleria mellonella, which is often used as an infection model. In contrast, the bacterium improved disease score and the absence of oxalate crystals in the lungs in the mouse model. This biocontrol interaction between oxalotrophic bacteria and A. niger represents a paradigm shift in the fight against opportunistic fungal pathogens, where the goal is to render the host environment less permissive to pathogen development One Sentence SummaryDemonstration of biocontrol as a therapeutic concept to combat Aspergillus niger with oxalotrophic bacteria in an animal infection model

microbiology↗

bioRxiv2021

Critical roles of ICOS in controlling Foxp3-expressing T follicular cell subsets during early-stage germinal center reactions

ICOS is a T cell costimulatory receptor critical for Tfh cell generation and function. However, the role of ICOS in Tfr cell differentiation remains unclear. Using Foxp3-Cre-mediated ICOS knockout (ICOS FC) mice, we show that ICOS deficiency in Treg-lineage cells drastically reduces the number of Tfr cells during GC reactions but has a minimal impact on conventional Treg cells. Single-cell transcriptome analysis of Foxp3+ cells at an early stage of the GC reaction suggests that ICOS normally inhibits Klf2 expression to promote follicular features including Bcl6 upregulation. Further, ICOS costimulation promotes nuclear localization of NFAT2, a known driver of CXCR5 expression. Notably, ICOS FC mice had an unaltered overall GC B cell output but showed signs of expanded autoreactive B cells along with elevated autoantibody titers. Thus, our study demonstrates that ICOS costimulation is critical for Tfr cell differentiation and highlights the importance of Tfr cells in maintaining humoral immune tolerance during GC reactions.

immunology↗