Biology subjects

Segura Munoz, R. R.

Publications and source records attributed to Segura Munoz, R. R..

4 recordsLinked to original sources

bioRxiv2026

Western diet suppresses canonical intestinal stem cells and reprograms c-Kit+ reserve stem cells via proinflammatory dysbiosis

While colorectal cancer (CRC) is thought to originate primarily from resident stem cells, diet heavily influences intestinal stem cell homeostasis and disease onset. In this study, we demonstrate that a Western-style diet (WSD) alters intestinal homeostasis by uncoupling canonical stemness from tumorigenesis. WSD exposure suppresses canonical Lgr5 stem cells while activating an alternative pool of facultative c-Kit secretory cells. Although these reprogrammed stem-like cells exhibit genotoxic stress, they remain proliferative under prolonged dietary exposure, suggesting increased susceptibility to tumor-initiating mutations. We identify diet-induced microbial shifts and the expansion of enterotoxigenic Bacteroides fragilis (ETBF) as the upstream driver. ETBF and its toxin fragilysin autonomously trigger multipotency in c-Kit+ cells through Wnt/{beta}-catenin and YAP signaling. Importantly, these alterations are fully reversible upon dietary intervention. Together, our results highlight a targetable dietary-microbial axis that shapes epithelial stemness and underscores the role of facultative stem cells in diet-induced CRC onset.

cell biology↗

bioRxiv2024

Collective dynamics of Escherichia coli growth under near-lethal acid stress

Many neutralophilic bacteria, including Escherichia coli, can withstand acidic conditions due to the action of several protective mechanisms. While the survival of E. coli under growth-inhibitory extreme acid stress is well understood, less is known about the physiology of E. coli growth under severe but permissive acidity. Here, we observed that growth of E. coli MG1655 in a rich medium with pH of 4.1 to 4.4 exhibits a characteristic multi-phasic growth pattern, consisting of an initial exponential elongation in the absence of cell division, followed by growth arrest and subsequent resumption of exponential growth. The duration of the growth arrest phase was strongly dependent on the pH of the medium, but also on the initial cell density of the culture, suggesting the collective nature of this phenomenon. Cell-density dependent multiphasic growth at the near-lethal pH, including the initial increase in cell volume associated with either elongation or widening of the cell body, was also observed for all tested natural E. coli isolates and for Salmonella enterica serovar Typhimurium. Such transient increase in volume apparently enables bacteria to induce acid resistance systems, including the lysine-dependent Cad system, to subsequently modify pH of the medium in the density-dependent manner. Consistent with the collective recovery, even a minor fraction of acid-tolerant cells could fully cross-protect acid-sensitive cells enabling them to resume growth in coculture. Thus, collective dynamics plays a central role in bacterial growth under near-lethal acid stress. ImportanceSince many E. coli and other Enterobacteriaceae isolates are gastrointestinal pathogens for humans, it is important to understand their growth under acidic conditions imposed by the host physiology in the stomach, colon, and inside macrophages. Here we show that E. coli growth under near-lethal acidic conditions is a collective phenomenon that critically depends on cell density. This collective behavior is favored by changes in cell morphology as a response to high acidity. The observed density dependence might have implications for pathogen proliferation in the acidic environment of the human gastrointestinal tract and possibly also for their interactions with immune cells.

microbiology↗

bioRxiv2019

Establishing the phenotypic basis of adherent-invasive Escherichia coli (AIEC) pathogenicity in intestinal inflammation

Background & AimsAdherent-invasive Escherichia coli (AIEC) are enriched in ileal Crohns disease patients and implicated in disease etiology. However, AIEC pathogenesis is poorly understood, and it is unclear if the expansion of these organisms contributes to inflammatory bowel disease (IBD). Questions also remain as to what extent the various in vitro phenotypes used to classify AIEC are pathologically relevant.\n\nMethodsWe utilized a combination of in vitro phenotyping and a murine model of intestinal inflammation to systematically relate AIEC phenotypes to pathogenicity for 30 mucosa-associated human-derived E. coli strains. In vitro assays used included survival/replication in and TNF- production by J774 macrophages as well as invasion/replication in Caco2 intestinal epithelial cells.\n\nResultsAIEC do not form a phenotypic group that is clearly separated from non-AIEC. However, E. coli strains displaying in vitro AIEC phenotypes caused, on average, more severe intestinal inflammation. Survival/replication of strains in J774 and Caco2 cells were positively correlated with disease in vivo, while adherence to Caco2 cells and TNF- production by J774 cells were not. Importantly, co-colonization with adherent non-AIEC strains ameliorated AIEC-mediated disease.\n\nConclusionOur findings do not support the existence of an AIEC pathovar that can be clearly separated from commensal E. coli. However, intracellular survival/replication phenotypes do contribute to murine intestinal inflammation, suggesting that the AIEC overgrowth observed in human IBD makes a causal contribution to disease. The ability to differentiate pathologically-relevant AIEC phenotypes from those that are not provides an important foundation for developing strategies to predict, diagnose and treat human IBD through characterizing and modulating patient E. coli populations.

microbiology↗

bioRxiv2017

A gut pathobiont synergizes with the microbiota to instigate inflammatory disease marked by immunoreactivity against other symbionts but not itself

Inflammatory bowel diseases (IBD) are likely driven by aberrant immune responses directed against the resident microbiota. Although IBD is commonly associated with a dysbiotic microbiota enriched in putative pathobionts, the etiological agents of IBD remain unknown. Using a pathobiont-induced intestinal inflammation model and a defined bacterial community, we provide new insights into the immune-microbiota interactions during disease. In our model system, the pathobiont Helicobacter bilis instigates disease following sub-pathological dextran sulfate sodium treatment. We show that H. bilis causes mild inflammation in mono-associated mice, but severe disease in the presence of a microbiota, demonstrating synergy between the pathobiont and microbiota in exacerbating pathology. Remarkably, inflammation depends on the presence of H. bilis, but is marked by a predominant Th17 response against specific members of the microbiota and not the pathobiont, even upon the removal of the most immune-dominant taxa. Neither increases in pathobiont burden nor unique changes in immune-targeted microbiota member abundances are observed during disease. Collectively, our findings demonstrate that a pathobiont instigates inflammation without being the primary target of a Th17 response or by altering the microbiota community structure. Moreover, our findings point toward monitoring pathobiont-induced changes in microbiota immune targeting as a new concept in IBD diagnotics.

immunology↗