Biology subjects

Simister, R. L.

Publications and source records attributed to Simister, R. L..

5 recordsLinked to original sources

bioRxiv2022

The dietary fiber guar gum ameliorates experimental autoimmune encephalomyelitis via attenuated Th1 activation and differentiation

Dietary fibers are potent modulators of immune responses that can restrain inflammation in multiple disease contexts. However, dietary fibers encompass a biochemically diverse family of carbohydrates, and it remains unknown how different fiber sources influence immunity. In a head-to-head comparison of four different high-fiber diets, we demonstrate a unique and potent ability of guar gum to reduce neuroinflammation in experimental autoimmune encephalomyelitis (EAE), a T cell-mediated mouse model of multiple sclerosis. CD4+ T cells from guar gum-fed mice have blunted Th1-skewing, reduced migratory capacity, and limited activation and proliferative capabilities. These changes are not explained by guar gum-specific alterations to the microbiota at the 16S rRNA level, nor by specific alterations in short chain fatty acids. These findings demonstrate specificity in the host response to fiber sources, and define a new pathway of fiber-induced CD4+ T cell immunomodulation that protects against pathologic neuroinflammation.

immunology↗

bioRxiv2022

Virus Infection Causes Intestinal Dysbiosis to Promote Type 1 Diabetes Onset

Autoimmune disorders like type 1 diabetes (T1D) are complex diseases caused by numerous factors including both genetic variance and environmental influences. Two such exogenous factors, intestinal microbial composition and enterovirus infection, have been independently associated with T1D onset in both humans and animal models. Since environmental factors rarely work in isolation, we examined the cross-talk between the microbiome and Coxsackievirus B4 (CVB4), an enterovirus that accelerates T1D onset in non-obese diabetic (NOD) mice. We demonstrate that CVB4-infection induced restructuring of the intestinal microbiome prior to T1D onset that was associated with thinning of the mucosal barrier, bacterial translocation to the pancreatic lymph node, and increased detection of circulating and intestinal commensal-reactive antibodies. Notably, the CVB4-induced change in community composition was strikingly similar to that of uninfected NOD mice that spontaneously developed diabetes, thus implying a mutual "diabetogenic" microbiome. Furthermore, fecal microbiome transfer (FMT) of the diabetogenic microbiota from CVB4-infected mice was sufficient to enhance T1D susceptibility in naive NOD recipients. These findings support a model whereby CVB infection disrupts the microbiome and intestinal homeostasis in a way that promotes activation of autoreactive immune cells and T1D.

microbiology↗

bioRxiv2020

STAT1-dependent tolerance of intestinal viral infection

Recent evidence indicates that viral components of the microbiota can contribute to intestinal homeostasis and protection from local inflammatory or infectious insults. However, host-derived mechanisms that maintain tolerance to the virome remain largely unknown. Here, we use colonization with the model commensal murine norovirus (MNV CR6) to interrogate host-directed mechanisms of viral tolerance, and show that STAT1 is a central coordinator of tolerance following CR6 colonization. STAT1 restricts CR6 replication to the intestinal tract, prevents systemic viral-induced tissue damage and disease, and regulates antiviral CD4+ and CD8+ T cell responses. In contrast to systemic viral pathogens that drive T cell mediated immunopathology in STAT1-deficient mice, our data indicates that loss of CD4+ or CD8+ T cells and their associated effector functions has no effect on CR6-induced disease. However, therapeutic administration of an antiviral compound to limit viral replication prevented viral-induced tissue damage and death despite ongoing dysregulated antiviral T cell responses. Collectively, our data uncouple the requirement for STAT1-mediated regulation of antiviral T cell responses from innate immune-mediated restriction of viral replication that is necessary for intestinal viral tolerance.

immunology↗

bioRxiv2019

Phylogenetic and structural diversity of aromatically dense pili from environmental metagenomes

Electroactive type IV pili, or e-pili, are used by some microbial species for extracellular electron transfer. Recent studies suggest that e-pili may be more phylogenetically and structurally diverse than previously assumed. Here, we used updated aromatic density thresholds ([≥]9.8% aromatic amino acids, [≤]22-aa aromatic gaps, and aromatic amino acids at residues 1, 24, 27, 50 and/or 51, and 32 and/or 57) to search for putative e-pilin genes in metagenomes from diverse ecosystems with active microbial metal cycling. Environmental putative e-pilins were diverse in length and phylogeny, and included truncated e-pilins in Geobacter spp., as well as longer putative e-pilins in Fe(II)-oxidizing Betaproteobacteria and Zetaproteobacteria.\n\nOriginality and SignificanceElectroactive pili (e-pili) are used by microorganisms to respire solid metals in their environment through extracellular electron transfer. Thus, e-pili enable microbes to occupy specific environmental niches. Additionally, e-pili have important potential for biotechnological applications. Currently the repertoire of known e-pili is small, and their environmental distribution is largely unknown. Using sequence analysis, we identified numerous genes encoding putative e-pili from diverse anoxic, metal-rich ecosystems. Our results expand the diversity of putative e-pili in environments where metal oxides may be important electron acceptors for microbial respiration.

microbiology↗

bioRxiv2016

Shifting microbial communities sustain multi-year iron reduction and methanogenesis in ferruginous sediment incubations

Reactive Fe(III) minerals can influence methane (CH4) emissions by inhibiting microbial methanogenesis or by stimulating anaerobic CH4 oxidation. The balance between Fe(III) reduction, methanogenesis, and methane oxidation in ferruginous Archean and Paleoproterozoic oceans would have controlled CH4 fluxes to the atmosphere, thereby regulating the capacity for CH4 to warm the early Earth under the Faint Young Sun. We studied CH4 and Fe cycling in anoxic incubations of ferruginous sediment from the ancient ocean analogue Lake Matano, Indonesia over three successive transfers (500 days total). Iron reduction, methanogenesis, methane oxidation, and microbial taxonomy were monitored in treatments amended with ferrihydrite or goethite. After three dilutions, Fe(III) reduction persisted only in bottles with ferrihydrite. Enhanced CH4 production was observed in the presence of goethite, highlighting the potential for reactive Fe(III)-oxides to inhibit methanogenesis. Supplementing the media with hydrogen, nickel and selenium did not stimulate methanogenesis. There was limited evidence for Fe(III)-dependent CH4 oxidation, although some incubations displayed CH4-stimulated Fe(III)-reduction. 16S rRNA profiles continuously changed over the course of enrichment, with ultimate dominance of unclassified members of the order Desulfuromonadales in all treatments. Microbial diversity decreased markedly over the course of incubation, with subtle differences between ferrihydrite and goethite amendments. These results suggest that Fe(III)-oxide mineralogy and availability of electron donors could have led to spatial separation of Fe(III)-reducing and methanogenic microbial communities in ferruginous marine sediments, potentially explaining the persistence of CH4 as a greenhouse gas throughout the first half of Earth history.

microbiology↗