Mathias L Richard

French National Institute for Agriculture, Food, and Environment (INRAE) | INRAE · Microbiologie de l'Alimentation au Service de la Santé Humaine (MICALIS)

Introduction Antibiotic effects on gut bacteria have been widely studied, but very little is known about the consequences of such treatments on the mycobiota, the fungal part of the microbiota and how the length of administration influences both microbiota. Here, we examined the effect of antibiotics (ATB) on the composition of bacterial and fungal...

Introduction: Staphylococcus epidermidis is a commensal bacterium ubiquitously present on human skin. This species is considered as a key member of the healthy skin microbiota, involved in the defense against pathogens, modulating the immune system, and involved in wound repair. Simultaneously, S. epidermidis is the second cause of nosocomial infe...

Background: Effects of antibiotics on gut bacteria have been widely studied, but very little is known about the consequences of such treatments on the fungal microbiota (mycobiota). It is commonly believed that fungal load increases in the gastrointestinal tract following antibiotic treatment, but better characterization is clearly needed of how a...

The gut microbiota is now recognized as a key parameter affecting the host’s anti-cancer immunosurveillance and ability to respond to immunotherapy. Therefore, optimal modulation for preventive and therapeutic purposes is very appealing. Diet is one of the most potent modulators of microbiota, and thus nutritional intervention could be exploited to...

Silver biodistribution and gut toxicity of two commercially available colloidal silver products, Mesosilver™ and AgC, were evaluated in male mice. AgC is composed solely of ionic silver (Ag+) while Mesosilver™...

The composition of the microbiota is the focus of many recent publications describing the effects of the microbiota on host health. In recent years, research has progressed further, investigating not only the diversity of genes and functions but also metabolites produced by microorganisms composing the microbiota of various niches and how these met...

Objective: The extent to which tryptophan (Trp) metabolism alterations explain or influence the outcome of inflammatory bowel diseases (IBDs) is still unclear. However, several Trp metabolism end-products are essential to intestinal homeostasis. Here, we investigated the role of metabolites from the kynurenine pathway. Design: Targeted quantitat...

The gut microbiota is now recognized as a key parameter affecting the host’s anti-cancer immunosurveillance and ability to respond to immunotherapy. Therefore, optimal modulation for preventive and therapeutic purposes is very appealing. Diet is one of the most potent modulators of microbiota, and thus nutritional intervention could be exploited to...

Objectives Inflammatory bowel disease (IBD) results from a combination of genetic predisposition, dysbiosis of the gut microbiota and environmental factors, leading to alterations in the gastrointestinal immune response and chronic inflammation. Caspase recruitment domain 9 ( Card9 ), one of the IBD susceptibility genes, has been shown to protect a...

IntroductionFungal microbiota's involvement in the pathogenesis of Crohn's disease (CD) is incompletely understood. The terminal ileum is a predilection site both for primary involvement and recurrences of CD. We, therefore, assessed the mucosa-associated mycobiota in the inflamed and non-inflamed ileum in patients with CD.Methods The mucosa-associ...

Food processes use different microorganisms, from bacteria to fungi. Yeast strains have been extensively studied, especially Saccharomyces cerevisiae. However, to date, very little is known about the potential beneficial effects of molds on gut health as part of gut microbiota. We undertook a comprehensive characterization of five mold strains, Pen...

Background Innate immunity genes have been reported to affect susceptibility to inflammatory bowel diseases (IBDs) and colitis in mice. Dectin-1, a receptor for fungal cell wall β-glucans, has been clearly implicated in gut microbiota modulation and modification of the susceptibility to gut inflammation. Here, we explored the role of Dectin-1 and D...

Objectives Inflammatory bowel disease (IBD) results from a combination of genetic predisposition, dysbiosis of the gut microbiota and environmental factors, leading to alterations in the gastrointestinal immune response and chronic inflammation. Caspase recruitment domain 9 ( Card9 ), one of the IBD susceptibility genes, has been shown to protect a...

Gut interleukin-17A (IL-17)-producing γδ T cells are tissue-resident cells that are involved in both host defense and regulation of intestinal inflammation. However, factors that regulate their functions are poorly understood. In this study, we find that the gut microbiota represses IL-17 production by cecal γδ T cells. Treatment with vancomycin, a...

Malassezia is the most prevalent fungus identified in the human skin microbiota; originally described at the end of the nineteenth century, this genus is composed of at least 14 species. The role of Malassezia on the skin remains controversial because this genus has been associated with both healthy skin and pathologies (dermatitis, eczema, etc.)....

The gut microbiota is a dense and diverse ecosystem that is involved in many physiological functions as well as in disease pathogenesis. It is dominated by bacteria, which have been extensively studied in the past 15 years; however, other microorganisms, such as fungi, phages, archaea and protists, are also present in the gut microbiota. Exploratio...

Objective Loss of the Crohn’s disease predisposing NOD2 gene results in an intestinal microenvironment conducive for colonisation by attaching-and-effacing enteropathogens. However, it remains elusive whether it relies on the intracellular recruitment of the serine-threonine kinase RIPK2 by NOD2, a step that is required for its activation of the tr...

Drug resistance and cellular adhesion are two key elements of both dissemination and prevalence of the human fungal pathogen Candida albicans. Smi1 belongs to a family of hub proteins conserved among the fungal kingdom whose functions in cellular signaling affect morphogenesis, cell wall synthesis and stress resistance. The data presented here indi...

Background: Host-microbe balance maintains intestinal homeostasis and strongly influences inflammatory conditions such as inflammatory bowel diseases (IBD). Here we focused on bacteria-fungi interactions and their implications on intestinal inflammation, a poorly understood area. Methods: Dextran sodium sulfate (DSS)-induced colitis was assessed...

Dietary lipids favor the growth of the pathobiont Bilophila wadsworthia, but the relevance of this expansion in metabolic syndrome pathogenesis is poorly understood. Here, we showed that B. wadsworthia synergizes with high fat diet (HFD) to promote higher inflammation, intestinal barrier dysfunction and bile acid dysmetabolism, leading to higher gl...

The extent to which microbiota alterations define or influence the outcome of metabolic diseases is still unclear, but the byproducts of microbiota metabolism are known to have an important role in mediating the host-microbiota interaction. Here, we identify that in both pre-clinical and clinical settings, metabolic syndrome is associated with the...

Gut microbiota dysbiosis has been associated with inflammatory bowel diseases (IBD). In colorectal cancer, the gut microbiota has also been recognized as potentially involved in aggravating or favoring the tumor development. However, very little is known on the structure and role of the microbiota in colitis associated cancer (CAC), an important co...

Background and Aims: Clostridium difficile infection (CDI) is a common complication in inflammatory bowel disease (IBD) and has been associated with poor IBD outcome. Intestinal microbiota composition in IBD patients with CDI has not been specifically evaluated to date. Methods: The fecal microbiota of 56 IBD patients, including 8 in flare with con...

Objective In association with innate and adaptive immunity, the microbiota controls the colonisation resistance against intestinal pathogens. Caspase recruitment domain 9 (CARD9), a key innate immunity gene, is required to shape a normal gut microbiota. Card9–/– mice are more susceptible to the enteric mouse pathogen Citrobacter rodentium that mimi...

Purpose of review: Inflammatory bowel diseases (IBDs) develop as a result of a combination of genetic predisposition, dysbiosis of the gut microbiota, and environmental influences. Here, we describe an example of how caspase recruitment domain 9 (CARD9), one of the numerous IBD susceptibility genes, participate to colitis susceptibility by shaping...

CARD9 et colite : un pont entre dysbiose et immunité

Complex interactions between the host and the gut microbiota govern intestinal homeostasis but remain poorly understood. Here we reveal a relationship between gut microbiota and caspase recruitment domain family member 9 (CARD9), a susceptibility gene for inflammatory bowel disease (IBD) that functions in the immune response against microorganisms....

Objective: The bacterial intestinal microbiota plays major roles in human physiology and IBDs. Although some data suggest a role of the fungal microbiota in IBD pathogenesis, the available data are scarce. The aim of our study was to characterise the faecal fungal microbiota in patients with IBD. Design: Bacterial and fungal composition of the f...

Background & aims: Gut microbiota is involved in many physiological functions and its imbalance is associated with several diseases, particularly with inflammatory bowel diseases. Mucosa-associated microbiota could have a key role in induction of host immunity and in inflammatory process. Although the role of fungi has been suggested in inflammato...

Studying host-microbiota interactions are fundamental to understanding the mechanisms involved in intestinal homeostasis and inflammation. In this work, we analyzed these interactions in mice that were mono-associated with six microorganisms that are representative of inflammatory bowel disease (IBD)-associated dysbiosis: the bacteria Bacteroides t...

Candida albicans is an opportunistic pathogen. It adheres to mammalian cells through a variety of adhesins that interact with hosts ligands. The spatial organization of these adhesins on the cellular interface is however poorly understood, mainly because of the lack of an instrument able to track single molecules on single cells. In this context, t...

: The prevalence of inflammatory bowel diseases (IBD) has been steadily increasing since 1960. They are widespread throughout Europe, North America, China, and Japan and are emerging as a global disease. The equilibrium among epithelial cells, the immune system, and the related microbiota seems to be paramount in ensuring the absence of these IBD....

Biofilm formation is an important virulence trait of the pathogenic yeast Candida albicans. We have combined gene overexpression, strain barcoding and microarray profiling to screen a library of 531 C. albicans conditional overexpression strains (∼10% of the genome) for genes affecting biofilm development in mixed-population experiments. The overex...

Cell wall proteins are central to the virulence of Candida albicans. Hwp1, Hwp2 and Rbt1 form a family of hypha-associated cell surface proteins. Hwp1 and Hwp2 have been involved in adhesion and other virulence traits but Rbt1 is still poorly characterized. To assess the role of Rbt1 in the interaction of C. albicans with biotic and abiotic surface...

Glycosylphosphatidylinositol (GPI)-anchored proteins are an important class of cell wall proteins in Candida albicans because of their localization and their function, even if more than half of them have no characterized homolog in the databases. In this study, we focused on the IFF protein family, investigating their exposure on the cell surface a...

In fungi, ambient pH sensing relies on the conserved Rim101 signalling pathway. All components of the pathway have been shown to be functionally conserved in the pathogenic yeast Candida albicans except for Rim9p which, in other fungi, has been suggested to be involved in this process. Here we report that, in C. albicans, the RIM9 homologue is requ...

The outer layer of the Candida albicans cell wall is enriched in highly glycosylated proteins. The major class, the GlycosylPhosphatidylInositol (GPI)-anchored proteins are tethered to the wall by GPI-anchor remnants and include adhesins, glycosyltransferases, yapsins and superoxide dismutases. In silico analysis suggested that C. albicans possesse...

The Candida albicans gpi7/gpi7 null mutant strain (Deltagpi7), which is affected in glycosylphosphatidylinositol (GPI) anchor biosynthesis, showed a reduced virulence following systemic infection of C57BL/6 mice. In vitro production of TNF-alpha, IL-6 and IL-1beta by macrophages in response to Deltagpi7 cells was significantly increased as compared...

There are two types of membrane proteins: the integral membrane proteins and the lipid-anchored proteins. Integral membrane proteins contain one or several transmembrane do- mains that allow for the formation of hydrophobic -helices, which ultimately embed the protein in a lipid bilayer. We count four types of lipid-anchored proteins divided into t...

Vps28p and Vps32p act in both the endocytic and the pH signaling pathways in yeasts and are required for Candida albicans virulence. Here, we show that deletions of VPS28 and VPS32 increase the susceptibility of C. albicans to cell wall disruption agents, echinocandin and azole antifungal agents.

Hyphal growth is prevalent during most Candida albicans infections. Current cell division models, which are based on cytological analyses of C. albicans, predict that hyphal branching is intimately linked with vacuolar inheritance in this fungus. Here we report the molecular validation of this model, showing that a specific mutation that disrupts v...

Biofilm formation plays a key role in the life cycles and subsistence of many microorganisms. For the human fungal pathogen Candida albicans, biofilm development is arguably a virulence trait, because medical implants that serve as biofilm substrates are significant risk factors for infection. The development of C. albicans biofilms in vitro procee...

The chlamydospore is a distinctive morphological feature of the fungal pathogen Candida albicans that can be induced to form in oxygen-limited environments and has been reported in clinical specimens. Chlamydospores are not produced by the model yeasts Saccharomyces cerevisiae and Schizosaccharomyces pombe, so there is limited understanding of the...

Glycosylphosphatidylinositol (GPI)-anchoring represents a mechanism for attaching proteins to the cell surface of all eukaryotic cells. Two localizations of GPI proteins have been observed in the yeasts Saccharomyces cerevisiae and Candida albicans: plasma membrane and cell wall. The signals and the mechanisms involved in this differential targetin...

Glycosylphosphatidylinositol (GPI)-anchored proteins are involved in cell wall integrity and cell-cell interactions. We disrupted the Candida albicans homologue of the Saccharomyces cerevisiae GPI7/LAS21 gene, which encodes a GPI anchor-modifying activity. In the mutant and on solid media, the yeast-to-hyphae transition was blocked, whereas chlamyd...

The yeast Yarrowia lipolytica is distantly related to Saccharomyces cerevisiae, can be genetically modified, and can grow in both haploid and diploid states in either yeast, pseudomycelial, or mycelial forms, depending on environmental conditions. Previous results have indicated that the STEand RIM pathways, which mediate cellular switching in othe...

The yeast Yarrowia lipolytica is distantly related to Saccharomyces cerevisiae, can be genetically modified, and can grow in both haploid and diploid states in either yeast, pseudomycelial, or mycelial forms, depending on environmental conditions. Previous results have indicated that the STE and RIM pathways, which mediate cellular switching in oth...