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Differential gene expression and adherence of Escherichia coli O157:H7 in vitro and in ligated pig intestines.

Yin X, Zhu J, Feng Y, Chambers JR, Gong J, Gyles CL - PLoS ONE (2011)

Bottom Line: It was found that decreased adherence in vitro by bacteria grown in MB was mainly due to lactose, possibly implicating the involvement of carbon catabolite repression (CCR).When bacteria were grown in MB and Brain Heart Infusion with NaHCO(3) (BHIN) plus lactose, pH was reduced to 5.5-5.9 and there was a significant decrease in expression of the locus of enterocyte effacement (LEE) genes eae, tir, espD, grlA/R and ler, and an increase in cya (cAMP), and two negative regulators of the LEE, gadE and hfq.Presence of lactose resulted in decreased expression of LEE genes and the failure of EHEC O157:H7 to adhere to epithelial cells in vitro but this repression was overcome in vivo.

View Article: PubMed Central - PubMed

Affiliation: Guelph Food Research Center, Agriculture and Agri-Food Canada, Guelph, Ontario, Canada.

ABSTRACT

Background: Escherichia coli O157:H7 strain 86-24 grown in MacConkey broth (MB) shows almost no adherence to cultured epithelial cells but adheres well in pig ligated intestines. This study investigated the mechanisms associated with the difference between in-vitro and in-vivo adherence of the MB culture.

Methodology/principal findings: It was found that decreased adherence in vitro by bacteria grown in MB was mainly due to lactose, possibly implicating the involvement of carbon catabolite repression (CCR). Expression of selected virulence-related genes associated with adherence and CCR was then examined by quantitative PCR. When bacteria were grown in MB and Brain Heart Infusion with NaHCO(3) (BHIN) plus lactose, pH was reduced to 5.5-5.9 and there was a significant decrease in expression of the locus of enterocyte effacement (LEE) genes eae, tir, espD, grlA/R and ler, and an increase in cya (cAMP), and two negative regulators of the LEE, gadE and hfq. Putative virulence genes stcE, hlyA, ent and nleA were also decreased in vitro. Reversal of these changes was noted for bacteria recovered from the intestine, where transcripts for qseF and fis and putative virulence factors AidA(15), TerC and Ent/EspL2 were significantly increased, and transcripts for AIDA(48), Iha, UreC, Efa1A, Efa1B, ToxB, EhxA, StcE, NleA and NleB were expressed at high levels.

Conclusions/significance: Presence of lactose resulted in decreased expression of LEE genes and the failure of EHEC O157:H7 to adhere to epithelial cells in vitro but this repression was overcome in vivo. CCR and/or acidic pH may have played a role in repression of the LEE genes. Bacterial pathogens need to integrate their nutritional metabolism with expression of virulence genes but little is known of how this is done in E. coli O157:H7. This study indicates one aspect of the subject that should be investigated further.

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Schematic model of LEE gene regulation.Actions via cAMP-CRP, hfq and gadE in EHEC O157:H7 grown in lactose/bile salts, low pH and MacConkey in vitro (A), actions and the signalling cascade leading to AE and pathogenesis by the pathogen in the intestinal environment (B). The lines that end with arrowheads indicate positive effects; lines that end with crossbars indicate negative effects. Dashed lines indicate hypothetical interactions. The up- and down- arrows indicate up-regulated or down-regulated genes found in this study.
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pone-0017424-g007: Schematic model of LEE gene regulation.Actions via cAMP-CRP, hfq and gadE in EHEC O157:H7 grown in lactose/bile salts, low pH and MacConkey in vitro (A), actions and the signalling cascade leading to AE and pathogenesis by the pathogen in the intestinal environment (B). The lines that end with arrowheads indicate positive effects; lines that end with crossbars indicate negative effects. Dashed lines indicate hypothetical interactions. The up- and down- arrows indicate up-regulated or down-regulated genes found in this study.

Mentions: A model of the lactose effect via cAMP, GadE and Hfq in the repression of LEE genes and other adherence related genes is presented in Fig. 7, in which cAMP, GadE and Hfq may be major control factors in LEE gene expression. Obviously, prior culture conditions determined the adherence phenotypes, due to the underlying transcriptomic profiles as determined by the culture conditions. It seemed that, even during the 6 h of the in vitro adherence assay, these transcriptomic profiles were not restored by the assay medium and by contact with the cultured cells.


Differential gene expression and adherence of Escherichia coli O157:H7 in vitro and in ligated pig intestines.

Yin X, Zhu J, Feng Y, Chambers JR, Gong J, Gyles CL - PLoS ONE (2011)

Schematic model of LEE gene regulation.Actions via cAMP-CRP, hfq and gadE in EHEC O157:H7 grown in lactose/bile salts, low pH and MacConkey in vitro (A), actions and the signalling cascade leading to AE and pathogenesis by the pathogen in the intestinal environment (B). The lines that end with arrowheads indicate positive effects; lines that end with crossbars indicate negative effects. Dashed lines indicate hypothetical interactions. The up- and down- arrows indicate up-regulated or down-regulated genes found in this study.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3046156&req=5

pone-0017424-g007: Schematic model of LEE gene regulation.Actions via cAMP-CRP, hfq and gadE in EHEC O157:H7 grown in lactose/bile salts, low pH and MacConkey in vitro (A), actions and the signalling cascade leading to AE and pathogenesis by the pathogen in the intestinal environment (B). The lines that end with arrowheads indicate positive effects; lines that end with crossbars indicate negative effects. Dashed lines indicate hypothetical interactions. The up- and down- arrows indicate up-regulated or down-regulated genes found in this study.
Mentions: A model of the lactose effect via cAMP, GadE and Hfq in the repression of LEE genes and other adherence related genes is presented in Fig. 7, in which cAMP, GadE and Hfq may be major control factors in LEE gene expression. Obviously, prior culture conditions determined the adherence phenotypes, due to the underlying transcriptomic profiles as determined by the culture conditions. It seemed that, even during the 6 h of the in vitro adherence assay, these transcriptomic profiles were not restored by the assay medium and by contact with the cultured cells.

Bottom Line: It was found that decreased adherence in vitro by bacteria grown in MB was mainly due to lactose, possibly implicating the involvement of carbon catabolite repression (CCR).When bacteria were grown in MB and Brain Heart Infusion with NaHCO(3) (BHIN) plus lactose, pH was reduced to 5.5-5.9 and there was a significant decrease in expression of the locus of enterocyte effacement (LEE) genes eae, tir, espD, grlA/R and ler, and an increase in cya (cAMP), and two negative regulators of the LEE, gadE and hfq.Presence of lactose resulted in decreased expression of LEE genes and the failure of EHEC O157:H7 to adhere to epithelial cells in vitro but this repression was overcome in vivo.

View Article: PubMed Central - PubMed

Affiliation: Guelph Food Research Center, Agriculture and Agri-Food Canada, Guelph, Ontario, Canada.

ABSTRACT

Background: Escherichia coli O157:H7 strain 86-24 grown in MacConkey broth (MB) shows almost no adherence to cultured epithelial cells but adheres well in pig ligated intestines. This study investigated the mechanisms associated with the difference between in-vitro and in-vivo adherence of the MB culture.

Methodology/principal findings: It was found that decreased adherence in vitro by bacteria grown in MB was mainly due to lactose, possibly implicating the involvement of carbon catabolite repression (CCR). Expression of selected virulence-related genes associated with adherence and CCR was then examined by quantitative PCR. When bacteria were grown in MB and Brain Heart Infusion with NaHCO(3) (BHIN) plus lactose, pH was reduced to 5.5-5.9 and there was a significant decrease in expression of the locus of enterocyte effacement (LEE) genes eae, tir, espD, grlA/R and ler, and an increase in cya (cAMP), and two negative regulators of the LEE, gadE and hfq. Putative virulence genes stcE, hlyA, ent and nleA were also decreased in vitro. Reversal of these changes was noted for bacteria recovered from the intestine, where transcripts for qseF and fis and putative virulence factors AidA(15), TerC and Ent/EspL2 were significantly increased, and transcripts for AIDA(48), Iha, UreC, Efa1A, Efa1B, ToxB, EhxA, StcE, NleA and NleB were expressed at high levels.

Conclusions/significance: Presence of lactose resulted in decreased expression of LEE genes and the failure of EHEC O157:H7 to adhere to epithelial cells in vitro but this repression was overcome in vivo. CCR and/or acidic pH may have played a role in repression of the LEE genes. Bacterial pathogens need to integrate their nutritional metabolism with expression of virulence genes but little is known of how this is done in E. coli O157:H7. This study indicates one aspect of the subject that should be investigated further.

Show MeSH
Related in: MedlinePlus