Biology subjects

Palm, N.

Publications and source records attributed to Palm, N..

3 recordsLinked to original sources

bioRxiv2026

Helicobacter pylori allelic variation in cell surface genes influences human exoproteome binding and stomach tissue adherence

Helicobacter pylori, the primary etiological agent of gastric cancer, requires chronic infection to promote severe disease. Throughout colonization, the bacteria accumulate genetic variation, which can reshape the interaction between host and pathogen. In this study, we probed adherence as one important characteristic of this relationship. We leveraged a panel of H. pylori strains, representing both inter- and intra-host diversity, and BASEHIT, a comprehensive barcoded yeast display library of the human exoproteome, to evaluate the human exoprotein binding characteristics of H. pylori. We identified a set of lineage-correlated binding phenotypes and a set of polymorphic cell surface-associated loci that we predict to govern heterogeneous binding. We also identified a general increase in gastric tissue adherence during mouse passage and structural modifications in the O-antigen component lipopolysaccharide. Subsequent sequence analyses identified C-terminal repeat length reduction in either futB or glycosyltransferase family 25 galactose transferases as sufficient to alter lipopolysaccharide. Shorter repeat variants were favored during both acute and chronic colonization and conferred a colonization advantage in coinfection. Our data indicate that shorter enzymes, and the resulting shorter O-antigen repeats, are favored during infection. We hypothesize that repeat length polymorphisms modulate enzyme efficiency and disrupt the balance of competing reactions required for O-antigen synthesis. ImportanceIn this study, we used a high throughput assay to evaluate the adherence of genetically diverse Helicobacter pylori isolates to human proteins they may encounter in the stomach. We showed that more closely related H. pylori strains bind human proteins similarly. We linked changes in bacterial binding to genetic differences affecting cell surface components. In particular, H. pylori strains passaged through mice exhibited increased adherence to stomach tissue, which we associated with structural variation in the enzymes responsible for synthesizing the O-antigen portion of lipopolysaccharide. We also showed that shorter enzyme variants produce distinct O-antigen structures that enhance colonization of the mouse stomach.

microbiology↗

bioRxiv2024

Children Who Develop Celiac Disease Exhibit Distinct Metabolic Pathways Among Their Gut Microbiota Years Before Diagnosis

Celiac disease (CD) is an autoimmune condition caused by a loss of tolerance to gluten in genetically predisposed individuals. While 30-40% of people possess the predisposing alleles, only 1-2% of the population is diagnosed with CD. This indicates environmental factors play a role in the pathogenesis of the disease, however the trigger of gluten tolerance loss is unknown. The gut microbiome composition of CD patients differs in comparison to their healthy counterparts; however, a causal link has not been established. In this study, we examined the alterations in the composition of the gut microbiota in a retrospective, longitudinal cohort of 10 children at age 1, matched for sex, human leukocyte antigen (HLA) genotype and breastfeeding duration. All samples were obtained from the pediatric donors prior to diagnosis (CD progressors). We used Ig-A sequencing combined with 16S sequencing for samples obtained at age 1. We also identified the functional metabolic pathways enriched in CD progressors compared to the healthy controls at ages 1, 2.5 (n=15-16) and 5 (n=9-13) using data from a similar study that we previously completed. Our findings demonstrate that CD progressors have ASV-level alterations in their gut microbiome as early as the first year of life, including the increased presence of some taxa that have been previously been reported to be enriched in CD. Using PICRUSt analysis, we also showed that inflammatory- and pathogenicity-related functions are enriched in CD progressors gut microbiome years before diagnosis. These pathways include glycine, serine and threonine metabolism, N-glycan biosynthesis and fatty acid biosynthesis and beta-lactam resistance, which are potentially contributing to chronic inflammation in CD. Overall, our results indicate distinct metabolic pathways enriched in the gut microbiome of CD progressors years before diagnosis. Understanding these pathways could advance our understanding of CD pathogenesis and its link to the gut microbiome.

microbiology↗

bioRxiv2018

IgA-deficient humans exhibit gut microbiota dysbiosis despite production of compensatory IgM

Immunoglobulin A is the dominant antibody isotype found in mucosal secretions and enforces host-microbiota symbiosis in mice, yet selective IgA-deficiency (sIgAd) is the most common primary immunodeficiency in humans and is often described as asymptomatic. Here, we determined the effects of IgA deficiency on human gut microbiota composition and evaluated the possibility that secretion of IgM can compensate for a lack of secretory IgA. We used 16S rRNA gene sequencing and bacterial cell sorting to evaluate gut microbiota composition and IgA or IgM coating of the gut microbiota in 15 sIgAd subjects and 15 matched controls. Although sIgAd subjects secreted a significant amount of IgM into the intestinal lumen, this was insufficient to fully compensate for the lack of secretory IgA. Indeed, sIgAd subjects displayed an altered gut microbiota composition as compared to healthy controls, which was characterized by a trend towards decreased overall microbial diversity and significant shifts in the relative abundances of specific microbial taxa. While IgA targets a defined subset of the microbiota via high-level coating, compensatory IgM binds a broader subset of the microbiota in a less targeted manner. We conclude that IgA plays a critical and non-redundant role in controlling gut microbiota composition in humans and that secretory IgA has evolved to maintain a diverse and stable gut microbial community that promotes human health, enhances resistance to infection, and is resilient to perturbation.

immunology↗