Browsing by Subject "Gastrointestinal Tract"
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Item Analysis of Bacterial-Host Interactions Between Campylobacter jejuni and the Avian Host During Commensalism(2009-06-15) Bingham-Ramos, Lacey Kathleen; Hendrixson, David R.Campylobacter jejuni is a leading cause of bacterial enteritis in humans throughout the world. In contrast to the disease seen in humans upon infection, C. jejuni promotes an asymptomatic, intestinal colonization of many animals, especially avian species, to result in commensalism. The primary route of transmission to humans is through the consumption or handling of undercooked poultry meats, making C. jejuni of particular importance to the agricultural industry. The direct interplay between C. jejuni and the natural avian host was examined to better understand the interactions that contribute to commensalism. We analyzed the colonization dynamics of C. jejuni over 28 days and identified a previously uncharacterized prolonged, robust colonization of the bursa of Fabricius, a major lymphoid organ. C. jejuni localized to the mucus layer lining the epithelium of the bursal lumen, with no invasion of or damage to host tissue apparent. However, C. jejuni was detected invading the cecal epithelium of chicks but only at day 1 post-infection, which may contribute to the observed transient, infection of the spleen and liver. Additionally, certain colonization factors of C. jejuni were shown to promote persistence in specific organs. Mutants lacking catalase and the cytolethal distending toxin demonstrated a reduction in levels in the bursa but not the ceca during prolonged colonization, whereas an unencapsulated mutant showed a global colonization defect of all organs. These findings suggest that persistent colonization of the bursa and the ceca, and the ability of the avian host to largely confine C. jejuni to mucosal surfaces may be specific for the development of commensalism. Separate analyses of additional colonization factors of C. jejuni revealed the importance of two putative cytochrome c peroxidases (CCP), DocA and Cjj0382, in promoting efficient cecal colonization. Further analysis of DocA and Cjj0382 revealed that both proteins have typical characteristics of CCPs, as they are periplasmic proteins with heme-dependent peroxidase activity. Our data suggest that although DocA and Cjj0382 have characteristics of CCPs, they likely perform different physiological functions for the bacterium during colonization. Overall, this study enhances our understanding of the interactions between C. jejuni and a natural host that contribute to the development of commensalism.Item The Characterization of the Fucose Sensing Kinase (FUSK) and the Fucose Sensing Response Regulator (FUSR) and Their Role in Virulence Regulation in Enterohemorrhagic Escherichia Coli O157:H7(2013-01-17) Pacheco, Alline Roberta; Sperandio, VanessaEHEC causes outbreaks of bloody diarrhea worldwide, by colonizing the human large intestine, where it forms attaching and effacing (AE) lesions on the intestinal epithelium. AE lesion development requires the presence of the locus of enterocyte effacement (LEE) that encodes for a molecular syringe, a type three secretion system (T3SS), which translocates effectors to the host cell. Expression of the LEE is controlled by the AI-3/Epi/NE interkingdom signaling cascade. The two-component systems QseBC and QseEF are at the core of the AI-3/Epi/NE signaling, controlling expression of flagellar motility genes, the LEE and type 3 secreted effectors in response to AI-3 and the catecholamine hormones Epi and NE. The network of regulatory proteins that form the AI-3/Epi/NE continues to expand, as shown by recent studies from our laboratory. Microarray analyses indicate that a putative two-component system (TCS), herein named FusKR, is repressed by QseBC and QseEF. FusK is the histidine kinase and FusR is the response regulator. In this work, we started to unravel the role of FusKR in EHEC pathogenicity. We constructed isogenic knockouts of fusK and fusR, and investigated their participation in virulence gene regulation in EHEC. Microarray analysis shows that deletion of fusK and fusR alters transcription of virulence and metabolic genes. Phenotypic analyses show that fusK- and fusR- strains are hypervirulent in vitro, overexpress the LEE genes and produces higher amounts of the T3 secreted protein EspB. Nonetheless, the fusK mutant is attenuated for colonization of the mammalian intestine. Biochemical studies revealed that FusK senses fucose. Fucose is an important carbon source for commensal and pathogenic bacteria during intestinal colonization. Transcriptional analyses shows that FusKR signal transduction system regulates fucose utilization indirectly, through regulation of the predicted membrane transporter Z0461, involved in optimal fucose uptake. Gut commensal Bacteroides thetaiomicron (B.theta) degrades mucin, releasing free monosaccharides, including fucose, into the gut lumen. Co-culture of B.theta and EHEC on mucin indicates that this commensal supplies mucin-derived fucose to EHEC, reducing expression of the LEE. Our studies demonstrate that a novel TCS, FusKR, modulates intestinal colonization by EHEC, and it is involved in complex interactions with the microbiota during infection.Item Engineered E. Coli That Detect and Respond to Gut Inflammation Through Nitric Oxide Sensing(2014-07-25) Archer, Eric Jeffry; Tu, Benjamin; Süel, Gürol M.; Mangelsdorf, David J.; Hooper, Lora V.; Gardner, Kevin H.Within the last several years, advances in synthetic biology have allowed for the development of re-programmed microorganisms that perform useful tasks in areas like fuel production, bioremediation, and medicine. Several engineered microorganisms are in pre-clinical development for the treatment of human diseases, but may face critical limitations that decrease their utility in medicine due to adverse events like sepsis, caused by the introduction of bacteria within patients. Here I describe the design, construction, and characterization of a synthetic genetic network that is intended for use by E. coli within lumen of the intestine, which is presumed to be a safer location than other tissues, such as blood, for the introduction of engineered microbes. The synthetic gene regulatory circuit described here regulates gene expression through the activation of a permanent DNA switch in response to nitric oxide produced by inducible nitric oxide synthase. The detection of nitric oxide initiates the expression of a DNA recombinase, causing the permanent genetic rearrangement of a short DNA segment containing a gene promoter, allowing for the regulation of output gene expression upon nitric oxide sensing. Here I demonstrate that E. coli containing this synthetic genetic circuit respond to nitric oxide as designed from both chemical nitric oxide donors and from injured mouse intestinal explants. This synthetic genetic circuit could be optimized for clinical use by allowing E. coli to reliably detect and treat inflammation in patients with inflammatory bowel disease, but the circuit described herein now serves as the proof-of-concept for both bacterial sensing of mammalian inflammation and for the use of DNA recombinases to translate transient environmental signals into permanent responses in engineered bacteria.Item Factors Governing Gastrointestinal Colonization of Candida albicans(December 2021) Mishra, Animesh Anand; Hendrixson, David R.; Hooper, Lora V.; Winter, Sebastian E.; Koh, Andrew Y.Candida albicans can colonize the human gastrointestinal tract (GI) and cause disseminated infections in immunocompromised hosts. Depletion of specific gut commensal microbiota is associated with or results in increased C. albicans burden in the gut and increased likelihood of dissemination in human patients and mice, respectively. The exact mechanisms by which gut microbiota mediate C. albicans colonization resistance in the gut, however, are unknown. Here, we show that gut microbiota-derived short chain fatty acids (SCFA) directly inhibit C. albicans growth in vitro. SCFA inhibit C. albicans hexose uptake and induce intracellular acidification. In contrast, SCFA promote C. albicans GI colonization resistance in vivo but only when an intact gut microbiome is present. SCFA induce gut microbiota composition changes that promote C. albicans colonization resistance. Commensal gut microbiota unable to produce SCFA have a diminished capacity to reduce C. albicans GI colonization. Prebiotic therapy results in increased GI SCFA levels which enhance C. albicans GI clearance. This work also describes two C. albicans isolates 529L and CHN1 that can stably colonize the murine GI tract without the use of antibiotics. These clinical isolates have a higher resistance to antimicrobial peptide CRAMP compared to the most commonly studied C. albicans laboratory strain SC5314. Thus, the work sheds light on mechanisms that might be critical in governing C. albicans gastrointestinal colonization levels. It provides mechanistic insights into the importance of gut microbiota-derived metabolites in maintaining C. albicans colonization resistance and may have therapeutic implications for modulating C. albicans gastrointestinal colonization levels in order to prevent invasive candidiasis in immunocompromised patients. Further, C. albicans strain-specific difference in colonization ability appears to depend on the sensitivity to these host immune effectors. The described isolates can further serve as valuable tools to probe the mechanisms of C. albicans gastrointestinal colonization without the intervention of any antibiotics.Item Gastrointestinal toxicity with NSAIDs in 2004: a revised approach to risk reduction(2004-11-11) Cryer, ByronItem NSAIDs and the gastrointestinal tract(1995-10-12) Cryer, ByronItem Unique Aspects of Intestinal Biology That Influence Enteric Virus Infection(2021-05-01T05:00:00.000Z) Woods Acevedo, Mikal Aaron; Orchard, Robert C.; Pfeiffer, Julie K.; Schoggins, John W.; Winter, Sebastian E.Enteric viruses are human pathogens that pose a significant global health problem. In this work, I explore how unique facets of host biology influence enteric virus infection, ranging from intestinal microbiota to circadian rhythms. To examine these factors, I used coxsackievirus B3 (CVB3) and poliovirus, which serve as a powerful model viruses to understand virus-host interactions. CVB3 and poliovirus are nonenveloped single-stranded positive-sense RNA viruses, which spread through the fecal-oral route. While many enteric virus infections are mild, some can be severe or even fatal. Thus it is important to study which factors impact enteric virus infection. Throughout my dissertation I used a variety of mouse models to answer a multitude of questions related to what factors influence enteric virus infection. To study the microbiota-mediated enhancement of CVB3 infection, I used different methods of antibiotic depletion in mice. We determined that two related enteric viruses, CVB3 and poliovirus, differ in their requirements of the microbiota. Furthermore, I studied the antiviral effects of antibiotics in vitro and in vivo and found that while antibiotics are not antiviral for CVB3 in cell culture, they are antiviral for CVB3 in a mouse model. Finally, by infecting mice at different times of day, we determined that host circadian rhythms influence enteric virus susceptibility. In conclusion, using model enteric viruses, such as CVB3 and poliovirus, I elucidated multiple unique aspects of host biology, ranging from microbiota to circadian rhythms, that influence viral replication and pathogenesis.Item Update on the gastrointestinal effects of the non-steroidal anti-inflammatory drugs(1999-08-19) Cryer, Byron