Biology subjects

Claesen, J.

Publications and source records attributed to Claesen, J..

12 recordsLinked to original sources

bioRxiv2026

Gut microbially produced phenolic acids have differential and sex-dependent effects on host metabolic health

Gut microbiota-derived metabolites are increasingly recognized as important regulators of host metabolism, but the specific functions of individual metabolites remain poorly understood. We therefore investigated the metabolic effects of two structurally related, phenylalanine-derived microbial metabolites phenylacetic acid (PAA) and phenylpropionic acid (PPA) in a mouse model of diet-induced obesity. Although clinical studies have linked PAA and its downstream product phenylacetylglutamine to metabolic disease, PAA did not alter body mass or adiposity in this model. Instead, it improved glucose tolerance selectively in male mice and markedly remodeled lipid metabolism in both sexes, reducing circulating triglycerides and acylcarnitines and activating hepatic PPAR--associated transcriptional programs associated with fatty acid {omega}-hydroxylation and peroxisomal lipid metabolism. Despite this extensive metabolic remodeling, PAA did not worsen hepatic steatosis, fibrosis, or markers of liver injury. By contrast, PPA had minimal effects on hepatic metabolic pathways but produced pronounced sex-dependent physiological responses, increasing adiposity in female mice and improving glucose tolerance in male mice. These findings show that structurally related microbial metabolites can have distinct, sex-dependent metabolic effects and highlight the need to define the actions of individual microbiome-derived metabolites when developing targeted therapies for metabolic disease.

systems biology↗

bioRxiv2026

Mechanistic prediction of fecal microbiota transplant engraftment and Clostridioides difficile colonization resistance with μODE

Shotgun metagenomics routinely resolves microbial community composition down to the strain level via metagenome-assembled genomes (MAGs), but translating these static catalogs into mechanistic, time-resolved understandings of ecosystem dynamics remains a critical computational bottleneck. Here, we present muODE, a fully automated framework that converts MAGs into dynamical simulations of community metabolism equipped with a composable, literature-grounded ecology layer, fundamentally designed to serve as a mechanistic hypothesis-testing engine. It employs dynamic flux balance analysis (dFBA) coupled to a shared extracellular pool and integrates a composable ecology layer capturing pH inhibition, time-varying antibiotic pharmacokinetics, bile-acid transformations, and spore dormancy. To evaluate the core engine, we cross-validated the dFBA machinery to machine precision against an independent reference implementation. We provide native export to the established COMETS engine for third-party verification. Benchmarking against two independent experimentally validated datasets confirmed that while monoculture growth is robustly captured, overflow secretion and directed community composition remain strictly bounded by the flux-routing limitations of max-biomass FBA. However, when applied to rate-modifying ecological feedback, muODE mechanistically and quantitatively reproduces bile-acid-mediated colonization resistance against Clostridioides difficile. With a single rate parameter calibrated so that baseline deoxycholate matched its measured physiological concentration, the framework reproduced the uncalibrated antibiotic-induced collapse of deoxycholate, with the calibrated inhibitor concentration coinciding with the independently set inhibitory threshold of the pathogen and driving a ~44x shift in the simulated pathogen-susceptibility ratio; bile-acid transformation is represented in the composable ecology layer rather than in the genome-scale stoichiometry. Finally, applying muODE end-to-end to a real longitudinal fecal microbiota transplant (FMT) yielding 139 de novo genome-scale metabolic models, the framework successfully recovered the clinical direction of treatment. By transparently diagnosing the structural competitive-exclusion bias that limits precise compositional prediction, muODE motivates the necessity of community-objective extensions while transitioning microbiome modeling from descriptive taxonomy toward testable, quantitatively-validated dynamic hypothesis testing, laying the essential mechanistic groundwork for the predictive engineering of safe, targeted ecological therapeutics. muODE is freely available at https://github.com/cumbof/muODE.

microbiology↗

bioRxiv2026

Oxidative stress induces E. coli aryl polyene expression, sensitizing the bacterial stress response and modulating the redox environment of innate immune cells

Aryl polyenes (APEs) are specialized polyunsaturated outer membrane lipids that protect their producers from oxidative stress and contribute to biofilm formation. APEs are produced by an abundant biosynthetic gene cluster (BGC) family conserved across Gram-negative bacterial clades. The APE biosynthesis pathway involves 11 different enzymes and cumulates in the attachment of APEs to an anchor molecule in the Gram-negative outer membrane. Unlike most other small molecule BGCs, the APE BGC does not contain a dedicated regulatory gene that controls production of its metabolically costly compounds. Building from our prior observations of APEs role in acute oxidative stress protection, we here use a uropathogenic Escherichia coli (UPEC) strain to show that APE expression conveys a potential competitive advantage characterized by increased early-stage growth, sensitization of the bacterial oxidative stress response, and dampening of the redox stress of innate immune cells after in vitro infection. Our data indicate that APEs could act as a UPEC fitness factor, and in future work we aim to study their contribution to overall bacterial pathogenicity and survival, as well as how APEs could facilitate the transition from an oxygen poor environment such as the gut to the oxygen rich environment of the urinary tract. ImportanceBacterial pathogens use various mechanisms to achieve a competitive advantage under harsh conditions such as upon interaction with their host. We studied the function of aryl polyenes (APEs), specialized polyunsaturated fatty acids in the outer membrane, in the context of a uropathogenic E. coli strain. APE expression is induced by an oxidative environment and contributes to early-stage growth and sensitization of the oxidative stress response. Furthermore, APE-expressing E. coli dampens the intracellular oxidative milieu of target host phagocytes. These findings suggest a role for APEs as a fitness factor, and create opportunities to study their in vivo function, and explore them as a potential drug target.

microbiology↗

bioRxiv2025

The antimicrobial metabolite nisin Z reduces intestinal tumorigenesis and modulates the cecal microbiome in ApcMin/+ mice

Nisin Z, an antimicrobial metabolite produced by Lactococcus lactis spp., has been safely used as a food preservative for many years. Nisin Z also showed promising activity against various cancer types in vitro, and significantly reduced tumor size in an ectopic head and neck cancer model. Here, we investigate the activity of nisin Z for colorectal cancer treatment and observed an in vitro reduction in cellular proliferation, and a moderate enhancement in cell death. We next analyzed the effect of oral nisin Z administration in the Apcmin/+ intestinal adenoma mouse model. We measured tumor burden along the gastrointestinal tract and observed a decrease in tumor burden in the middle region of the small intestine, but not in the lower region or colon. Since tumor progression in the Apcmin/+ model is exacerbated by an inflammatory environment, we next determined whether nisin Z impacts this in a direct or indirect manner. We show that nisin Z can directly reduce NF-{kappa}B activation in a dose-dependent manner. In addition, nisin Z impacted the cecal microbiome composition as well as microbiota-associated plasma metabolites, causing an overall shift towards a more health-associated profile. Interestingly, the Apcmin/+ genotype differentially impacted the nisin Z-mediated differences in cecal microbiome composition and plasma metabolites compared to wildtype animals. In summary, our data suggest that the reduction in small intestinal tumor burden could be due to nisin Zs contribution to a reduced pro-inflammatory environment. Future studies will reveal whether nisins localized effect is due to degradation of the peptidic compound in more distal regions of the gastrointestinal tract and focus on development of delivery systems to increase efficacy. ImportanceWith the increased incidence of colorectal cancer, especially among younger individuals, it is critical to study approaches that help with the prevention and treatment of this debilitating disease. Our study indicates that nisin Z, a bacterially produced peptide antibiotic, decreases the growth of colorectal cancer cells and moderately increases cell death in vitro. Oral administration of nisin Z in an intestinal adenoma mouse model revealed a reduction of tumor burden in the middle region of the small intestine. This decreased tumor burden might in part be attributed to a direct anti-inflammatory effect, as well as an indirect effect on the gut microbiota and their metabolites due to nisin Zs antibacterial activity. Overall, we demonstrate a potential activity for nisin Z in the prevention or amelioration of inflammation-associated colorectal cancer, underscoring the significance of investigating the properties of bacterial natural products in human health.

microbiology↗

bioRxiv2025

Gut microbial conversion of dietary elderberry extract to hydrocinnamic acid improves obesity-associated metabolic disorders

Obesity-associated metabolic disorders such as type 2 diabetes mellitus and metabolic dysfunction associated fatty liver disease are major global health concerns, yet current pharmacological treatments often present with major side-effects. Dietary interventions including polyphenol-rich foods offer a promising complementary option for obesity amelioration, but their efficacy is dependent on specific gut microbial metabolism and the underlying molecular mechanisms mostly remain elusive. Here, we demonstrated that dietary elderberry (Eld) extract abrogates the effects of an obesogenic diet in a gut microbiota-dependent manner, by preventing insulin resistance and reducing hepatic steatosis in mice. We developed a targeted, quantitative liquid chromatography-tandem mass spectrometry method for detection of gut bacterial polyphenol catabolites and identified hydrocinnamic acid as a key microbial metabolite, enriched in the portal vein plasma of Eld supplemented animals. Next, we showed that hydrocinnamic acid potently activates hepatic AMP-activated protein kinase , explaining its role in improved liver lipid homeostasis. Furthermore, we uncovered the metabolic pathway cumulating in hydrocinnamic acid production in the common gut commensal Clostridium sporogenes. Our characterization of hydrocinnamic acid as a diet-derived, and microbiota-dependent metabolite with insulin-sensitizing and anti-steatotic activities will contribute to microbiome-targeted dietary interventions to prevent and treat obesity-associated metabolic diseases.

microbiology↗

bioRxiv2021

A 3D printable device allowing fast and reproducible longitudinal preparation of mouse intestines

Accurate and reproducible analysis of mouse small and large intestinal lumen is key for research involving intestinal pathology in preclinical models. Currently, there is no easily accessible, standardized method that allows researchers of different skill levels to consistently dissect intestines in a time-efficient manner. Here, we describe the design and use of the 3D printed "Mouse Intestinal Slicing Tool" (MIST), which can be used to longitudinally prepare murine intestines for further analysis. We benchmarked the MIST against a commonly used procedure involving scissors to make a longitudinal cut along the intestines. Use of the MIST halved the time per mouse to prepare the intestines and outperformed alternative methods in smoothness of the cutting edge and general reproducibility. By sharing the plans for printing the MIST, we hope to contribute a uniformly applicable method for saving time and increasing consistency in studies of the mouse gastrointestinal tract.

pathology↗

bioRxiv2021

A gut microbial metabolite of dietary polyphenols reverses obesity-driven hepatic steatosis

The molecular mechanisms by which dietary fruits and vegetables confer cardiometabolic benefits remain poorly understood. Historically, these beneficial properties have been attributed to the antioxidant activity of flavonoids. Here, we reveal that the host metabolic benefits associated with flavonoid consumption actually hinge on gut microbial metabolism. We show that a single gut microbial flavonoid catabolite is sufficient to reduce diet-induced cardiometabolic disease burden in mice. Dietary supplementation with elderberry extract attenuated obesity and continuous delivery of the catabolite 4-hydroxphenylacetic acid was sufficient to reverse hepatic steatosis. Analysis of human gut metagenomes revealed that under one percent contains a flavonol catabolic pathway, underscoring the rarity of this process. Our study will impact the design of dietary and probiotic interventions to complement traditional cardiometabolic treatment strategies. One-Sentence SummarySelect gut microbes can metabolize flavonoids from a fruit and vegetable diet to monophenolic acids, which improve fatty liver disease. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=87 SRC="FIGDIR/small/460661v1_ufig1.gif" ALT="Figure 1"> View larger version (28K): org.highwire.dtl.DTLVardef@1c4f56borg.highwire.dtl.DTLVardef@1cc4be3org.highwire.dtl.DTLVardef@18a4af5org.highwire.dtl.DTLVardef@3f44a5_HPS_FORMAT_FIGEXP M_FIG C_FIG

microbiology↗

bioRxiv2021

A secondary metabolite drives intraspecies antagonism in a gut symbiont that is inhibited by peptidoglycan acetylation

The mammalian microbiome encodes numerous secondary metabolite biosynthetic gene clusters, yet their role in microbe-microbe interactions is unclear. Here, we characterized two polyketide synthase gene clusters (fun and pks) in the gut symbiont Limosilactobacillus reuteri. The pks, but not the fun cluster, encodes antimicrobial activity. Forty-one out of 51 L. reuteri strains tested are sensitive to Pks products, which was independent of strains host origin. The sensitivity to Pks was also established in intraspecies competition experiments in gnotobiotic mice. Comparative genome analyses between Pks-resistant and sensitive strains identified an acyltransferase gene (act) that is unique to Pks-resistant strains. Subsequent cell wall analysis of the wild-type and the act mutant strains showed that Act acetylates cell wall components. The pks mutants lost their competitive advantage and act mutants lost their Pks resistance in vivo. Thus, our findings provide insight into how closely related gut symbionts can compete and co- exist in the gastrointestinal tract.

microbiology↗

bioRxiv2020

A Novel Surgical Method for Continuous Intra-Portal Infusion of Gut Microbial Metabolites in Mice

Gut microbial-derived metabolites have been shown to play key roles in human physiology and disease. However, establishing mechanistic links between gut microbial metabolites and disease pathogenesis in animal models presents many challenges. The major route of absorption for microbe-derived small molecules is venous drainage via the portal vein to the liver. In the event of extensive liver first pass- or presystemic hepatic metabolism, the route of administration of these metabolites becomes critical. Here we describe a novel portal vein cannulation technique using a subcutaneously implanted osmotic pump to achieve continuous portal vein infusion in mice. First, the microbial metabolite trimethylamine (TMA) was administered over 4 weeks and compared to a vehicle control. Using a liquid chromatography-tandem mass spectrometry (LC-MS/MS), an increase in peripheral plasma levels of TMA and its host liver-derived co-metabolite trimethylamine-N-oxide (TMAO) were observed in a sexually-dimorphic manner. Next, 4-hydroxyphenylacetic acid (4-HPAA), a structurally distinct microbial metabolite that undergoes extensive hepatic first pass metabolism, was administered intraportally to examine effects on hepatic gene expression. As expected, there was no difference in peripheral plasma 4-HPAA levels yet liver tissue demonstrated higher levels of 4-HPAA when compared to the control group. More importantly, significant changes were observed in hepatic gene expression using an unbiased RNA sequencing approach. Collectively, this work describes a novel method for administering gut microbe-derived metabolites via the portal vein, mimicking their physiologic delivery in vivo. ImportanceRecent efforts have underscored the importance of the gut microbial community as a meta-endocrine organ impacting host physiology through systemic delivery of gut-microbial metabolites [Brown and Hazen, 2015]. Microbial metabolites are first delivered to the liver via the portal vein following venous drainage of the gastrointestinal tract. This route of absorption is often crucial by allowing the liver to biotransfrom these molecules prior to entering the peripheral circulation. Microbial metabolites are frequently studied in animal models by incorporation into diet or drinking water. This method falls short as inconsistent oral intake, inconsistent gastrointestinal absorption, and further modification of the metabolite by gut microbes yield imprecise levels of drug delivery. In efforts to overcome this, the physiological impact of microbial metabolites is often studied by intermittent exogenous administration of a metabolite in a non-physiologically relevant manner such as intravenous injection, intraperitoneal injection, or subcutaneous administration, all placing a relatively large proportion of the metabolite directly into the peripheral circulation. Although these approaches can effectively raise circulating metabolites levels in some cases, they do not mimic the natural delivery of gut microbial-derived small molecules through the portal circulation to the liver. Here we describe a novel surgical method to continuously deliver precise amounts of gut microbial metabolites intraportally to better recapitulate the natural systemic delivery route of microbial metabolites to the liver. This model will improve the interrogation of gut microbial metabolites and their associations to disease by providing an unmatched level of resolution when manipulating the portal blood metabolome.

microbiology↗

bioRxiv2020

Disruption of the gut microbiota attenuates epithelial ovarian cancer sensitivity to cisplatin therapy

Epithelial Ovarian Cancer (EOC) is the leading cause of gynecologic cancer death. Despite many patients achieving remission with first-line therapy, up to 80% of patients will recur and require additional treatment. Retrospective clinical analysis of OC patients indicates antibiotic use during chemotherapy treatment is associated with poor overall survival. We assessed whether antibiotic (ABX) therapy would impact growth of EOC and sensitivity to cisplatin in murine models. Immune competent or compromised mice were given control or ABX containing water (metronidazole, ampicillin, vancomycin, and neomycin) before being intraperitoneally injected with murine EOC cells. Stool was collected to confirm microbiome disruption and tumors were monitored, and cisplatin therapy was administered weekly until endpoint. EOC tumor-bearing mice demonstrate accelerated tumor growth and resistance to cisplatin therapy in ABX treated compared with nonABX treatment. Stool analysis indicated most gut microbial species were disrupted by ABX treatment except for ABX resistant bacteria. To test for role of the gut microbiome, cecal microbiome transplants (CMTs) of microbiota derived from ABX or nonABX treated mice were used to recolonize the microbiome of ABX treated mice. nonABX cecal microbiome was sufficient to ameliorate the chemoresistance and survival of ABX treated mice indicative of a gut derived tumor suppressor. Mechanistically, tumors from ABX treated compared to nonABX treated mice contained a high frequency of cancer stem cells that were augmented by cisplatin. These studies indicate an intact microbiome provides a gut derived tumor suppressor and maintains chemosensitivity that is disrupted by ABX treatment. SignificancePlatinum resistance is associated with poor prognosis and reduced therapeutic options for ovarian cancer patients. We identifed a tumor suppressive role of the gut microbiome that is disrupted upon antibiotic therapy.

cancer biology↗

bioRxiv2020

Identification of essential genes for Escherichia coli aryl polyene biosynthesis and function in biofilm formation

Aryl polyenes (APEs) are specialized polyunsaturated carboxylic acids that were identified in silico as the product of the most widespread family of bacterial biosynthetic gene clusters (BGCs). They are present in several Gram-negative host-associated bacteria, including multi-drug resistant human pathogens. Here, we characterize a biological function of APEs, focusing on the BGC from a uropathogenic Escherichia coli (UPEC) strain. We first perform a genetic deletion analysis to identify the essential genes required for APE biosynthesis. Next, we show that APEs function as fitness factors that increase protection from oxidative stress and contribute to biofilm formation. Together, our study highlights key steps in the APE biosynthesis pathway that can be explored as potential drug targets for complementary strategies to reduce fitness and prevent biofilm formation of multi-drug resistant pathogens.

microbiology↗

bioRxiv2019

Cutibacterium acnes antibiotic production shapes niche competition in the human skin microbiome

The composition of the skin microbiome varies widely among individuals sampled at the same body site. A key question is which molecular factors determine strain-level variability within sub-ecosystems of the skin. We used a genomics-guided approach to identify an antibacterial biosynthetic gene cluster in Cutibacterium acnes (formerly Propionibacterium acnes) that is widely distributed across individuals and skin sites. Experimental characterization of this cluster enabled the identification of a new thiopeptide antibiotic, cutimycin. Analysis of individual human skin hair follicles showed that cutimycin is an important factor regulating colonization resistance against Staphylococcus species.\n\nOne Sentence SummaryCutimycin, a thiopeptide antibiotic produced by a widespread skin commensal, reduces Staphylococcus colonization of human follicles.

microbiology↗