Biology subjects

Briandet, R.

Publications and source records attributed to Briandet, R..

5 recordsLinked to original sources

bioRxiv2023

Anti-S-layer monoclonal antibodies impact Clostridioides difficile physiology

Clostridioides difficile (C. difficile), a gram-positive anaerobic and spore-forming bacterium, is the leading cause of nosocomial antibiotic-associated diarrhea in adults and is characterized by high levels of recurrence and mortality. Surface-layer Protein A (SlpA), the most expressed protein on bacterial surface, plays a crucial role in the early stages of infection although its role in C. difficile physiology is yet to be fully understood. Anti-S-layer antibodies have been identified in the sera of convalescent patients and correlate with improved outcome of C. difficile infection (CDI). However, the precise mechanisms of how anti-S-layer antibodies can confer protection to the host remain unknown. In this study, we report the first monoclonal antibodies (mAbs) targeting S-layer of the reference strain 630. Characterization of these mAbs unravels important roles for S-layer protein in growth, toxin secretion, and biofilm formation with, surprisingly, opposite effects of different anti-SlpA mAbs on these functions. One anti-SlpA mAb impaired C. difficile growth and restored sensitivity to lysozyme-induced lysis. These findings suggest that anti-S-layer antibody responses may include protective and detrimental effects for the host and provide important insights for designing adequate S-layer-targeting therapeutics.

microbiology↗

bioRxiv2023

Spatially localized expression of glutamate decarboxylase gadB in Escherichia coli O157:H7 microcolonies in hydrogel matrix

Functional diversity within isogenic spatially organized bacterial populations has been shown to trigger emergent community properties such as stress tolerance. Taking advantage of confocal laser scanning microscopy combined with a transcriptional fluorescent fusion reporting at single cell scale the expression of the glutamic acid decarboxylase gadB in E. coli O157:H7, it was possible to visualize for the first-time spatial patterns of bacterial gene expression in microcolonies grown in a gelled matrix. The gadB gene is involved in E. coli tolerance to acidic conditions and its strong over-expression was observed locally on the periphery of embedded microcolonies grown in acidic hydrogels. This spatialization of gadB expression did not correlate with live/dead populations that appeared randomly distributed in the colonies. While the planktonic population of the pathogens was eradicated by an exposition to a pH of 2 (HCl) for 4h, mimicking a stomachal acidic stress, bacteria grown in gel-microcolonies were poorly affected by this treatment, in particular in conditions where gadB was spatially overexpressed. Consequences of these results for food safety are further discussed.

microbiology↗

bioRxiv2023

Multi-scale transcriptome unveils spatial organisation and temporal dynamics of Bacillus subtilis biofilms

Bacillus subtilis has been extensively used to study the molecular mechanisms behind the development and dispersal of surface bacterial multicellular communities. Well-structured spatially organised communities (colony, pellicle, and submerged biofilm) share some similarities, but also display considerable differences at the structural, chemical and biological levels. To unveil the spatial transcriptional heterogeneity between the different communities, we analysed by RNA-seq nine spatio-physiological populations selected from planktonic and spatially organised communities. This led to a global landscape characterisation of gene expression profiles uncovering genes specifically expressed in each compartmental population. From this mesoscale analysis and using fluorescent transcriptional reporter fusions, 17 genes were selected and their patterns of expression reported at single cell scale with time-lapse confocal laser scanning microscopy (CLSM). Derived kymographs allowed to emphasise spectacular mosaic gene expression patterns within a biofilm. A special emphasis on oppositely regulated carbon metabolism genes (gapA and gapB) permitted to pinpoint the coexistence of spatially segregated bacteria under either glycolytic or gluconeogenic regime in a same biofilm population. Altogether, this study gives novel insights on the development and dispersal of B. subtilis surface-associated communities.

microbiology↗

bioRxiv2023

Extracellular succinate induces spatially organized biofilm formation in Clostridioides difficile

Clostridioides difficile is the major cause of nosocomial diarrhea, which are associated with gut microbiome dysbiosis. Biofilms of C. difficile have been progressively linked to the pathogenesis of this bacterium and the recurrences of its infections. Though the number of conditions in which C. difficile biofilms are being produced is increasing, little is known about how and when biofilms are formed in the gut. Here we report that succinate, a metabolite abundantly produced by the dysbiotic gut microbiota, induces in vitro biofilm formation of C. difficile strains. We characterized the morphology and spatial composition of succinate-induced biofilms, and compared to non-induced or deoxycholate-induced biofilms, biofilms induced by succinate are significantly thicker, structurally more complex, and poorer in proteins and exopolysaccharides (EPS). We then applied transcriptomics and genetics to characterize the early stages of succinate-induced biofilm formation and we showed that succinate-induced biofilm results from major metabolic shifts and cell-wall composition changes. Similar to deoxycholate-induced biofilms, biofilms induced by succinate depend on the presence of a rapidly metabolized sugar. Finally, although succinate can be consumed by the bacteria, we found that the extracellular succinate is in fact responsible for the induction of biofilm formation through complex regulation involving global metabolic regulators and the osmotic stress response. In the context of human gut dysbiosis, succinate can limit bacterial infections through the control of innate immune responses. Collectively, our results suggest that succinate is an intestinal signal which can drive the biofilm formation and persistence of C. difficile in the gut and increase the risk of relapse.

microbiology↗

bioRxiv2022

Comparative genome analysis of Enterococcus cecorum reveals intercontinental spread of a lineage of clinical poultry isolates.

Enterococcus cecorum is an emerging pathogen responsible for osteomyelitis, spondylitis, and femoral head necrosis causing animal suffering, mortality, and requiring antimicrobial use in poultry. Paradoxically, E. cecorum is a common inhabitant of the intestinal microbiota of adult chickens. Despite evidence suggesting the existence of clones with pathogenic potential, the genetic and phenotypic relatedness of disease-associated isolates remains little investigated. Here, we sequenced and analyzed the genomes and characterized the phenotypes of more than 100 isolates, the majority of which were collected over the last ten years in 16 French broiler farms. Comparative genomics, genome-wide association study, and measured susceptibility to serum, biofilm forming capacity, and adhesion to chicken type II collagen were used to identify features associated with clinical isolates. We found that none of the tested phenotypes could discriminate origin of the isolates or phylogenetic group. Instead, we found that most clinical isolates are grouped phylogenetically and our analyses selected six genes that discriminate 94% of isolates associated with disease from those that are not. Analysis of the resistome and the mobilome revealed that multidrug-resistant clones of E. cecorum cluster in few clades and that integrative conjugative elements and genomic islands are the main carriers of antimicrobial resistance. This comprehensive genomic analysis shows that disease-associated clones of E. cecorum belong mainly to one phylogenetic clade. IMPORTANCEEnterococcus cecorum is an important pathogen in poultry worldwide. It causes a number of locomotor disorders and septicemia, particularly in fast-growing broilers. Animal suffering, antimicrobial use, and associated economic losses require a better understanding of disease-associated E. cecorum isolates. To address this need, we performed whole genome sequencing and analysis of a large collection of isolates responsible for outbreaks in France. By providing the first dataset on the genetic diversity and resistome of E. cecorum strains circulating in France, we pinpoint an epidemic lineage probably also circulating elsewhere and which should be targeted preferentially by preventive strategies in order to reduce the burden of E. cecorum-related diseases.

genomics↗