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Ethanolamine Signaling Promotes Salmonella Niche Recognition and Adaptation during Infection.

Anderson CJ, Clark DE, Adli M, Kendall MM - PLoS Pathog. (2015)

Bottom Line: Our findings reveal that S.Typhimurium co-opts ethanolamine as a signal to coordinate metabolism and then virulence.Because the ability to sense ethanolamine is a conserved trait among pathogenic and commensal bacteria, our work indicates that ethanolamine signaling may be a key step in the localized adaptation of bacteria within their mammalian hosts.

View Article: PubMed Central - PubMed

Affiliation: Department of Microbiology, Immunology, and Cancer Biology, University of Virginia School of Medicine, Charlottesville, Virginia, United States of America.

ABSTRACT
Chemical and nutrient signaling are fundamental for all cellular processes, including interactions between the mammalian host and the microbiota, which have a significant impact on health and disease. Ethanolamine is an essential component of cell membranes and has profound signaling activity within mammalian cells by modulating inflammatory responses and intestinal physiology. Here, we describe a virulence-regulating pathway in which the foodborne pathogen Salmonella enterica serovar Typhimurium (S. Typhimurium) exploits ethanolamine signaling to recognize and adapt to distinct niches within the host. The bacterial transcription factor EutR promotes ethanolamine metabolism in the intestine, which enables S. Typhimurium to establish infection. Subsequently, EutR directly activates expression of the Salmonella pathogenicity island 2 in the intramacrophage environment, and thus augments intramacrophage survival. Moreover, EutR is critical for robust dissemination during mammalian infection. Our findings reveal that S. Typhimurium co-opts ethanolamine as a signal to coordinate metabolism and then virulence. Because the ability to sense ethanolamine is a conserved trait among pathogenic and commensal bacteria, our work indicates that ethanolamine signaling may be a key step in the localized adaptation of bacteria within their mammalian hosts.

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Related in: MedlinePlus

The impact of ethanolamine on SPI-2 expression in vitro.(A) qRT-PCR of ssrB from RNA isolated from the S. Typhimurium (SL1344) grown in SPI-2 inducing medium with ethanolamine (EA) supplementation as indicated. Statistical significance is shown relative to cells grown without EA supplementation. (B) qRT-PCR of ssrB from RNA isolated from the S. Typhimurium (SL1344) grown in DMEM with EA supplementation as indicated. Statistical significance is shown relative to cells grown without EA supplementation. (C) qRT-PCR of eutR from RNA isolated from S. Typhimurium (AJK61) grown in DMEM with supplementation as indicated or after phagocytosis in RAW macrophages. Statistical significance relative to cells grown in DMEM is indicated. (D) qRT-PCR of eutS from RNA isolated from S. Typhimurium (AJK61) grown in DMEM with supplementation as indicated or after phagocytosis in RAW macrophages. Statistical significance relative to cells grown in DMEM is indicated. (E) qRT-PCR of ssrB from RNA isolated from the S. Typhimurium strain (AJK61) grown in DMEM with supplementation as indicated or after phagocytosis in RAW macrophages. Statistical significance relative to cells grown in DMEM is indicated. For all, n = 3; error bars represent the geometric mean ± SD; strB was used as the endogenous control. *, P ≤ 0.05; **, P ≤ 0.005; ***, P ≤0.0005; P > 0.05 = ns.
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ppat.1005278.g003: The impact of ethanolamine on SPI-2 expression in vitro.(A) qRT-PCR of ssrB from RNA isolated from the S. Typhimurium (SL1344) grown in SPI-2 inducing medium with ethanolamine (EA) supplementation as indicated. Statistical significance is shown relative to cells grown without EA supplementation. (B) qRT-PCR of ssrB from RNA isolated from the S. Typhimurium (SL1344) grown in DMEM with EA supplementation as indicated. Statistical significance is shown relative to cells grown without EA supplementation. (C) qRT-PCR of eutR from RNA isolated from S. Typhimurium (AJK61) grown in DMEM with supplementation as indicated or after phagocytosis in RAW macrophages. Statistical significance relative to cells grown in DMEM is indicated. (D) qRT-PCR of eutS from RNA isolated from S. Typhimurium (AJK61) grown in DMEM with supplementation as indicated or after phagocytosis in RAW macrophages. Statistical significance relative to cells grown in DMEM is indicated. (E) qRT-PCR of ssrB from RNA isolated from the S. Typhimurium strain (AJK61) grown in DMEM with supplementation as indicated or after phagocytosis in RAW macrophages. Statistical significance relative to cells grown in DMEM is indicated. For all, n = 3; error bars represent the geometric mean ± SD; strB was used as the endogenous control. *, P ≤ 0.05; **, P ≤ 0.005; ***, P ≤0.0005; P > 0.05 = ns.

Mentions: Next, we investigated whether ethanolamine impacted SPI-2 expression. SsrB is a SPI-2 encoded transcriptional regulator that is required for expression of all the SPI-2-encoded genes, as well as for expression of effectors and virulence genes encoded outside of SPI-2 [28–31]. To test the influence of ethanolamine, we measured expression of ssrB in low magnesium, minimal medium, a condition that induces SPI-2 expression [32] (S2 Fig) without supplementation or with supplementation of 250 μM or 5 mM ethanolamine. These concentrations were used because 250 μM ethanolamine was the lowest concentration with which we could readily detect EutR expression (S3 Fig), whereas 5 mM is similar to ethanolamine concentrations in the gastrointestinal tract [33]. When 250 μM ethanolamine was added to the SPI-2 inducing medium, expression of ssrB was significantly increased compared to medium without supplementation, but unchanged when 5 mM ethanolamine was added (Fig 3A). These data suggest that ethanolamine may enhance the response of S. Typhimurium in adapting to the intramacrophage environment. Expression of SPI-2 is tightly regulated and is induced specifically in the intracellular environment [34], or in conditions that mimic the intracellular environment. In accordance, ssrB expression was not induced in DMEM or LB when ethanolamine was supplemented to the medium (Fig 3B and S4 Fig), indicating that ethanolamine in and of itself does not override additional regulatory factors that direct ssrB expression. However, ssrB expression was decreased in DMEM with the addition of 5 mM ethanolamine (Fig 3B). Altogether these data raised the possibility that ethanolamine signaling enhances niche recognition.


Ethanolamine Signaling Promotes Salmonella Niche Recognition and Adaptation during Infection.

Anderson CJ, Clark DE, Adli M, Kendall MM - PLoS Pathog. (2015)

The impact of ethanolamine on SPI-2 expression in vitro.(A) qRT-PCR of ssrB from RNA isolated from the S. Typhimurium (SL1344) grown in SPI-2 inducing medium with ethanolamine (EA) supplementation as indicated. Statistical significance is shown relative to cells grown without EA supplementation. (B) qRT-PCR of ssrB from RNA isolated from the S. Typhimurium (SL1344) grown in DMEM with EA supplementation as indicated. Statistical significance is shown relative to cells grown without EA supplementation. (C) qRT-PCR of eutR from RNA isolated from S. Typhimurium (AJK61) grown in DMEM with supplementation as indicated or after phagocytosis in RAW macrophages. Statistical significance relative to cells grown in DMEM is indicated. (D) qRT-PCR of eutS from RNA isolated from S. Typhimurium (AJK61) grown in DMEM with supplementation as indicated or after phagocytosis in RAW macrophages. Statistical significance relative to cells grown in DMEM is indicated. (E) qRT-PCR of ssrB from RNA isolated from the S. Typhimurium strain (AJK61) grown in DMEM with supplementation as indicated or after phagocytosis in RAW macrophages. Statistical significance relative to cells grown in DMEM is indicated. For all, n = 3; error bars represent the geometric mean ± SD; strB was used as the endogenous control. *, P ≤ 0.05; **, P ≤ 0.005; ***, P ≤0.0005; P > 0.05 = ns.
© Copyright Policy
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC4643982&req=5

ppat.1005278.g003: The impact of ethanolamine on SPI-2 expression in vitro.(A) qRT-PCR of ssrB from RNA isolated from the S. Typhimurium (SL1344) grown in SPI-2 inducing medium with ethanolamine (EA) supplementation as indicated. Statistical significance is shown relative to cells grown without EA supplementation. (B) qRT-PCR of ssrB from RNA isolated from the S. Typhimurium (SL1344) grown in DMEM with EA supplementation as indicated. Statistical significance is shown relative to cells grown without EA supplementation. (C) qRT-PCR of eutR from RNA isolated from S. Typhimurium (AJK61) grown in DMEM with supplementation as indicated or after phagocytosis in RAW macrophages. Statistical significance relative to cells grown in DMEM is indicated. (D) qRT-PCR of eutS from RNA isolated from S. Typhimurium (AJK61) grown in DMEM with supplementation as indicated or after phagocytosis in RAW macrophages. Statistical significance relative to cells grown in DMEM is indicated. (E) qRT-PCR of ssrB from RNA isolated from the S. Typhimurium strain (AJK61) grown in DMEM with supplementation as indicated or after phagocytosis in RAW macrophages. Statistical significance relative to cells grown in DMEM is indicated. For all, n = 3; error bars represent the geometric mean ± SD; strB was used as the endogenous control. *, P ≤ 0.05; **, P ≤ 0.005; ***, P ≤0.0005; P > 0.05 = ns.
Mentions: Next, we investigated whether ethanolamine impacted SPI-2 expression. SsrB is a SPI-2 encoded transcriptional regulator that is required for expression of all the SPI-2-encoded genes, as well as for expression of effectors and virulence genes encoded outside of SPI-2 [28–31]. To test the influence of ethanolamine, we measured expression of ssrB in low magnesium, minimal medium, a condition that induces SPI-2 expression [32] (S2 Fig) without supplementation or with supplementation of 250 μM or 5 mM ethanolamine. These concentrations were used because 250 μM ethanolamine was the lowest concentration with which we could readily detect EutR expression (S3 Fig), whereas 5 mM is similar to ethanolamine concentrations in the gastrointestinal tract [33]. When 250 μM ethanolamine was added to the SPI-2 inducing medium, expression of ssrB was significantly increased compared to medium without supplementation, but unchanged when 5 mM ethanolamine was added (Fig 3A). These data suggest that ethanolamine may enhance the response of S. Typhimurium in adapting to the intramacrophage environment. Expression of SPI-2 is tightly regulated and is induced specifically in the intracellular environment [34], or in conditions that mimic the intracellular environment. In accordance, ssrB expression was not induced in DMEM or LB when ethanolamine was supplemented to the medium (Fig 3B and S4 Fig), indicating that ethanolamine in and of itself does not override additional regulatory factors that direct ssrB expression. However, ssrB expression was decreased in DMEM with the addition of 5 mM ethanolamine (Fig 3B). Altogether these data raised the possibility that ethanolamine signaling enhances niche recognition.

Bottom Line: Our findings reveal that S.Typhimurium co-opts ethanolamine as a signal to coordinate metabolism and then virulence.Because the ability to sense ethanolamine is a conserved trait among pathogenic and commensal bacteria, our work indicates that ethanolamine signaling may be a key step in the localized adaptation of bacteria within their mammalian hosts.

View Article: PubMed Central - PubMed

Affiliation: Department of Microbiology, Immunology, and Cancer Biology, University of Virginia School of Medicine, Charlottesville, Virginia, United States of America.

ABSTRACT
Chemical and nutrient signaling are fundamental for all cellular processes, including interactions between the mammalian host and the microbiota, which have a significant impact on health and disease. Ethanolamine is an essential component of cell membranes and has profound signaling activity within mammalian cells by modulating inflammatory responses and intestinal physiology. Here, we describe a virulence-regulating pathway in which the foodborne pathogen Salmonella enterica serovar Typhimurium (S. Typhimurium) exploits ethanolamine signaling to recognize and adapt to distinct niches within the host. The bacterial transcription factor EutR promotes ethanolamine metabolism in the intestine, which enables S. Typhimurium to establish infection. Subsequently, EutR directly activates expression of the Salmonella pathogenicity island 2 in the intramacrophage environment, and thus augments intramacrophage survival. Moreover, EutR is critical for robust dissemination during mammalian infection. Our findings reveal that S. Typhimurium co-opts ethanolamine as a signal to coordinate metabolism and then virulence. Because the ability to sense ethanolamine is a conserved trait among pathogenic and commensal bacteria, our work indicates that ethanolamine signaling may be a key step in the localized adaptation of bacteria within their mammalian hosts.

Show MeSH
Related in: MedlinePlus