<style draggable="fkPjs0"><noframes date-time="1dZvr3"><code dropzone="866pp"></code> Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The . gov means it’s official. Federal government websites often end in . gov or VSports app下载. mil. Before sharing sensitive information, make sure you’re on a federal government site. .

Https

The site is secure V体育官网. The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely. .

. 2020 May 3;11(3):364-380.
doi: 10.1080/19490976.2017.1421886. Epub 2018 Mar 1.

Adaptation of adherent-invasive E. coli to gut environment: Impact on flagellum expression and bacterial colonization ability

Gwladys Sevrin  1 , Sébastien Massier  1 , Benoit Chassaing  2 , Allison Agus  1 , Julien Delmas  1   3 , Jérémy Denizot  1   4 , Elisabeth Billard  1   4 , Nicolas Barnich  1   4
Affiliations

Adaptation of adherent-invasive E. coli to gut environment: Impact on flagellum expression and bacterial colonization ability

Gwladys Sevrin et al. Gut Microbes. .

"VSports在线直播" Abstract

The pathogenesis of Crohn's disease (CD) is multifactorial and involves genetic susceptibility, environmental triggers and intestinal microbiota VSports手机版. Adherent-invasive Escherichia coli (AIEC) are flagellated bacteria more prevalent in CD patients than in healthy subjects and promote chronic intestinal inflammation. We aim at deciphering the role of flagella and flagellin modulation by intestinal conditions. AIEC flagellum expression is required for optimal adhesion to and invasion of intestinal epithelial cells. Interestingly, differential flagellin regulation was observed between commensal E. coli (HS) and AIEC (LF82) strains: flagellum expression by AIEC bacteria, in contrast to that of commensal E. coli, is enhanced under intestinal conditions (the presence of bile acids and mucins). Flagella are involved in the ability of the AIEC LF82 strain to cross a mucus layer in vitro and in vivo, conferring a selective advantage in penetrating the mucus layer and reaching the epithelial surface. In a CEABAC10 mouse model, a non-motile mutant (LF82-ΔfliC) exhibits reduced colonization that is restored by a dextran sodium sulfate treatment that alters mucus layer integrity. Moreover, a mutant that continuously secretes flagellin (LF82-ΔflgM) triggers a stronger inflammatory response than the wild-type strain, and the mutant's ability to colonize the CEABAC10 mouse model is decreased. Overexpression of flagellin in bacteria in contact with epithelial cells can be detrimental to their virulence by inducing acute inflammation that enhances AIEC clearance. AIEC pathobionts must finely modulate flagellum expression during the infection process, taking advantage of their specific virulence gene regulation to improve their adaptability and flexibility within the gut environment. .

PubMed Disclaimer

Figures (VSports在线直播)

Figure 1.
Figure 1.
Deletion of fliC gene reduces AIEC ability to adhere to and invade Caco-2/TC7 cells. A: Cell-associated bacteria were quantified after a 3-h infection period. The results are expressed as the percentage of wild-type associated bacteria. B: Invasion ability was determined after gentamicin treatment for an additional hour. The results are expressed as the percentage of wild-type invasive bacteria. Each value is the mean ± standard error of mean (SEM) of at least three separate experiments. Statistical analysis were performed using one-way ANOVA with Tukey's multiple comparison test. P< 0.05 (*), P < 0.01 (**) and P < 0.001 (***).
Figure 2.
Figure 2.
AIEC LF82 strain can reach the intestinal epithelium of mono-colonized mice by flagellum expression, in contrast with the commensal E. coli strain HS. A: Confocal microscope examinations of intestinal tissues of mono-colonized mice for 2 weeks with wild-type LF82, LF82-ΔfliC or the commensal HS strain. Histological sections were immunostained for mucus (green), bacteria (red), actin (purple) and nucleic acids (blue). B: Distance between bacteria and epithelial cell monolayer was determined by using Zen 2011 version 7.1 software on immunostained sections. The data are presented as the mean ± SEM. Statistical analysis was performed using one-way ANOVA with Tukey's multiple comparison test. P < 0.01 (**) and P < 0.001 (***). C and D: Quantification of fliC and fimA expression by RT-qPCR in ileal tissue. The 16S rRNA gene was used as an internal standard to normalize the data. Bar indicates median.
Figure 3.
Figure 3.
Contact with mucus-hyperproducing HT-29-MTX cells activates fliC promoter in AIEC but not in commensal E. coli strain. The LF82 fliC gene promoter was cloned upstream of lacZ in the pRS550 plasmid, and the pRS550-pfliC construct was transformed into the LF82 and the commensal E. coli HS strains. Background β-galactosidase activity that was generated by a promoterless pRS550 construct was subtracted at each time point. A: Activation of fliC promoter by 1% cholic and deoxycholic acids (50/50) after 30 min, 3 h and 6 h in AIEC LF82 and E. coli HS strains harbouring the pRS550-pfliC plasmid. The results are expressed as the ratio of β-galactosidase activity in the presence of bile salts to those in the basal medium (20% 5x M9 broth, 20% LB and 60% Tris buffer). B: Promoter activity of LF82 or HS E. coli harbouring the pRS550-pfliC plasmid and associated with HT29 epithelial cells or mucus-hyperproducing HT29-MTX cells. The results are expressed as the ratio of β-galactosidase activity of associated bacteria to those of bacteria in the cell culture medium. The data are presented as the mean ± SEM of at least five independent experiments Statistical analysis were performed using one-way ANOVA with Tukey's multiple comparison test. P< 0.05 (*) and P< 0.005 (***). ns, not significant.
Figure 4.
Figure 4.
Flagella enhance LF82 access to intestinal epithelial cells in vitro and in vivo, A: Quantification of bacteria associated with intestinal epithelial HT29 cells or with mucus-hyperproducing intestinal epithelial HT29-MTX cells after 3 h of infection. Each value is the mean  ±  SEM of at least five independent experiments. Statistical analysis were performed using one-way ANOVA with Tukey's multiple comparison test. P< 0.05 (*). B and C: After antibiotic treatment, CEABAC10 transgenic mice were treated or not treated with 0.5% DSS. Mice were orally challenged for 3 consecutive days with 109 LF82 or LF82-ΔfliC CFUs, and (B) the number of mucosa-associated bacteria and (C) the amount of colonic pro-inflammatory keratinocyte-derived chemokine (KC) secretion were determined 4 days after the last infection. Statistical analysis were performed using Kruskal-Wallis with Dunn's multiple comparison test for B panel or one-way ANOVA with Tukey's multiple comparison test for C panel. P< 0.05 (*), P < 0.01 (**) and P < 0.001 (***). ns, not significant.
Figure 5.
Figure 5.
Deletion of flgM gene reduces LF82 adhesion to and invasion of intestinal epithelial Caco-2/TC7 cells but increases their interleukin-8 response, A: The numbers of cell-associated bacteria were quantified after a 3-h infection period. The results are expressed as the percentage of adherent wild-type LF82 bacteria. B: Invasion ability was determined after gentamicin treatment for an additional hour. The results are expressed as the percentage of invasive wild-type LF82 bacteria taken as 100%. C: Representative western blot analysis of flagellin release in the culture supernatant at 24h. Quantification of FliC band intensity standardize to total protein is shown in the top panel (representative from 4 independent experiments). D: Pro-inflammatory chemokine interleukin-8 secretion by Caco-2/TC7 cells after a 3-h infection. The data are presented as the mean ± SEM of at least four independent experiments Statistical analysis were performed using one-way ANOVA with Tukey's multiple comparison test. P <  0.05 (*),P <  0.01 (**) and P <  0.005 (***).
Figure 6.
Figure 6.
Modulation of flagellin synthesis by FlgM allows LF82 persistence and limits host inflammatory response. A and B: After antibiotic treatment, CEABAC10 transgenic mice were treated with 0.25% DSS. Their body weights were measured every day (A). Statistical analysis was performed using two-way ANOVA with Bonferroni's multiple comparison test. P< 0.05 (*),P< 0.01 (**) and P< 0.005 (***). Mice were orally challenged for two consecutive days with 109 LF82 or LF82-ΔflgM CFUs (grey arrows on graphs A and C). The colonization was assessed by quantifying bacteria in stool samples, which were counted on LB agar plates at days 4 and 6 (B). Bar indicates median. Statistical analysis was performed using Kruskal-Wallis with Dunn's multiple comparison test. P< 0.05. Mice were orally challenged again at day 6 (black arrow). C: Survival rate of mice during the experiment. D: After sacrifice, the pro-inflammatory keratinocyte-derived chemokine (KC) secretion by colonic tissue was measured. The data are presented as the mean ± SEM. Statistical analysis was performed using unpaired Student t test. P< 0.05 (*). E: Measure of serum antibodies raised against FliC in infected mice. Purified LF82 flagellin was electrophoresed in each lane of a 12% SDS-polyacrylamide gel and blotted to a nitrocellulose membrane. Diluted serum was used as the primary antibody. Quantification of band intensity was realized using the Image Lab software.
See this image and copyright information in PMC

VSports最新版本 - References

    1. Chassaing, B & Darfeuille-Michaud, A.. The commensal microbiota and enteropathogens in the pathogenesis of inflammatory bowel diseases. Gastroenterology 2011;140:1720–1728. - PubMed
    1. Kaser, A, Zeissig, S & Blumberg, RS. Inflammatory Bowel Disease. Annu. Rev. Immunol. 2010;28:573. - PMC - PubMed
    1. Xavier, RJ & Podolsky, DK. Unravelling the pathogenesis of inflammatory bowel disease. Nature 2007;448:427–434. - PubMed (V体育官网)
    1. Barnich, N & Darfeuille-Michaud, A. Role of bacteria in the etiopathogenesis of inflammatory bowel disease. World J. Gastroenterol. WJG 2007;13:5571. - V体育2025版 - PMC - PubMed
    1. Darfeuille-Michaud, A, et al. Presence of adherent Escherichia coli strains in ileal mucosa of patients with Crohn's disease. Gastroenterology 1998;115:1405–1413. - PubMed

Publication types

MeSH terms