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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

EutR in pathogen-microbiota-host interactions.(A) Schematic of the eut operon. (B) In vitro growth curve of S. Typhimurium WT (SL1344), ΔeutR (CJA009), or ΔeutB (CJA020) strains in LB without or with supplementation of 5 mM ethanolamine (EA). Each data point shows the average of three independent experiments. (C) qRT-PCR of eutR in WT or the ΔeutB (CJA020) S. Typhimurium strains grown in Dulbecco’s Modified Eagle Medium (DMEM) or DMEM supplemented with 5 mM EA. n = 3; error bars represent the geometric mean ± standard deviation (SD); strB was used as the endogenous control. (D-F) Competition assays between (D) ΔeutB::CmR (CJA018) and WT strains; (E) ΔeutR::CmR (CJA007) and WT strains; or (F) ΔeutR::CmR (CJA007) and ΔeutB (CJA020) strains. Mice were orogastrically inoculated with 1:1 mixtures of indicated strains. Colony forming units (cfu) were determined at indicated time points. Each bar represents a competition index (CI). Horizontal lines represent the geometric mean value ± standard error (SE) for each group (n = 2 litters (6–8 animals)). *, P ≤0.05; **, P ≤ 0.005; ***, P ≤0.0005; P > 0.05 = ns.
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ppat.1005278.g001: EutR in pathogen-microbiota-host interactions.(A) Schematic of the eut operon. (B) In vitro growth curve of S. Typhimurium WT (SL1344), ΔeutR (CJA009), or ΔeutB (CJA020) strains in LB without or with supplementation of 5 mM ethanolamine (EA). Each data point shows the average of three independent experiments. (C) qRT-PCR of eutR in WT or the ΔeutB (CJA020) S. Typhimurium strains grown in Dulbecco’s Modified Eagle Medium (DMEM) or DMEM supplemented with 5 mM EA. n = 3; error bars represent the geometric mean ± standard deviation (SD); strB was used as the endogenous control. (D-F) Competition assays between (D) ΔeutB::CmR (CJA018) and WT strains; (E) ΔeutR::CmR (CJA007) and WT strains; or (F) ΔeutR::CmR (CJA007) and ΔeutB (CJA020) strains. Mice were orogastrically inoculated with 1:1 mixtures of indicated strains. Colony forming units (cfu) were determined at indicated time points. Each bar represents a competition index (CI). Horizontal lines represent the geometric mean value ± standard error (SE) for each group (n = 2 litters (6–8 animals)). *, P ≤0.05; **, P ≤ 0.005; ***, P ≤0.0005; P > 0.05 = ns.

Mentions: Genes encoding for ethanolamine metabolism are clustered in the eut operon [18] (Fig 1A). In the Enterobacteriaceae, expression of this operon is regulated by the eut-encoded transcription factor EutR. EutR is constitutively expressed at low levels from its own promoter and binds to the promoter region immediately upstream of eutS. In the presence of ethanolamine and vitamin B12, EutR activates transcription of this operon [19,20]. In enterohemorrhagic Escherichia coli (EHEC), EutR senses ethanolamine to activate virulence gene expression in vitro, independently of ethanolamine metabolism [19,21,22]. To determine whether EutR influences S. Typhimurium disease progression during infection, we generated an eutR deletion strain (ΔeutR) that cannot sense ethanolamine as well as an eutB deletion strain (ΔeutB) that lacks the large subunit of the ethanolamine ammonia lyase, and thus is unable to catabolize ethanolamine. The eutR and eutB mutations did not result in a general loss of fitness, as the ΔeutR and ΔeutB strains exhibited no measurable growth defects in vitro (Fig 1B). Importantly, the eutB mutation is nonpolar as this mutant can respond to ethanolamine (Fig 1C). Subsequently, we performed competitive infections in which streptomycin-treated mice were orally infected with an equal mixture of wild type (WT) and ΔeutB (ΔeutB::CmR) strains or the WT and ΔeutR (ΔeutR::CmR) strains. S. Typhimurium infection presents as intestinal outgrowth, invasion of epithelial cells, and subsequent uptake by macrophages and dissemination to secondary lymphoid tissue. Therefore, to monitor the course of S. Typhimurium infection, we analyzed the number of recovered bacteria from the intestinal contents, the colon, and the spleen. At 2 and 4 days post infection (dpi), the ΔeutR and ΔeutB strains were significantly outcompeted by the WT strain in intestinal contents (Fig 1D and 1E). These data underscore the importance of ethanolamine metabolism in S. Typhimurium colonization of the intestinal tract, and these findings are consistent with previous work by Thiennimitr et al., who showed that ethanolamine metabolism provides a growth advantage to S. Typhimurium during intestinal colonization [17].


Ethanolamine Signaling Promotes Salmonella Niche Recognition and Adaptation during Infection.

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

EutR in pathogen-microbiota-host interactions.(A) Schematic of the eut operon. (B) In vitro growth curve of S. Typhimurium WT (SL1344), ΔeutR (CJA009), or ΔeutB (CJA020) strains in LB without or with supplementation of 5 mM ethanolamine (EA). Each data point shows the average of three independent experiments. (C) qRT-PCR of eutR in WT or the ΔeutB (CJA020) S. Typhimurium strains grown in Dulbecco’s Modified Eagle Medium (DMEM) or DMEM supplemented with 5 mM EA. n = 3; error bars represent the geometric mean ± standard deviation (SD); strB was used as the endogenous control. (D-F) Competition assays between (D) ΔeutB::CmR (CJA018) and WT strains; (E) ΔeutR::CmR (CJA007) and WT strains; or (F) ΔeutR::CmR (CJA007) and ΔeutB (CJA020) strains. Mice were orogastrically inoculated with 1:1 mixtures of indicated strains. Colony forming units (cfu) were determined at indicated time points. Each bar represents a competition index (CI). Horizontal lines represent the geometric mean value ± standard error (SE) for each group (n = 2 litters (6–8 animals)). *, P ≤0.05; **, P ≤ 0.005; ***, P ≤0.0005; P > 0.05 = ns.
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Related In: Results  -  Collection

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ppat.1005278.g001: EutR in pathogen-microbiota-host interactions.(A) Schematic of the eut operon. (B) In vitro growth curve of S. Typhimurium WT (SL1344), ΔeutR (CJA009), or ΔeutB (CJA020) strains in LB without or with supplementation of 5 mM ethanolamine (EA). Each data point shows the average of three independent experiments. (C) qRT-PCR of eutR in WT or the ΔeutB (CJA020) S. Typhimurium strains grown in Dulbecco’s Modified Eagle Medium (DMEM) or DMEM supplemented with 5 mM EA. n = 3; error bars represent the geometric mean ± standard deviation (SD); strB was used as the endogenous control. (D-F) Competition assays between (D) ΔeutB::CmR (CJA018) and WT strains; (E) ΔeutR::CmR (CJA007) and WT strains; or (F) ΔeutR::CmR (CJA007) and ΔeutB (CJA020) strains. Mice were orogastrically inoculated with 1:1 mixtures of indicated strains. Colony forming units (cfu) were determined at indicated time points. Each bar represents a competition index (CI). Horizontal lines represent the geometric mean value ± standard error (SE) for each group (n = 2 litters (6–8 animals)). *, P ≤0.05; **, P ≤ 0.005; ***, P ≤0.0005; P > 0.05 = ns.
Mentions: Genes encoding for ethanolamine metabolism are clustered in the eut operon [18] (Fig 1A). In the Enterobacteriaceae, expression of this operon is regulated by the eut-encoded transcription factor EutR. EutR is constitutively expressed at low levels from its own promoter and binds to the promoter region immediately upstream of eutS. In the presence of ethanolamine and vitamin B12, EutR activates transcription of this operon [19,20]. In enterohemorrhagic Escherichia coli (EHEC), EutR senses ethanolamine to activate virulence gene expression in vitro, independently of ethanolamine metabolism [19,21,22]. To determine whether EutR influences S. Typhimurium disease progression during infection, we generated an eutR deletion strain (ΔeutR) that cannot sense ethanolamine as well as an eutB deletion strain (ΔeutB) that lacks the large subunit of the ethanolamine ammonia lyase, and thus is unable to catabolize ethanolamine. The eutR and eutB mutations did not result in a general loss of fitness, as the ΔeutR and ΔeutB strains exhibited no measurable growth defects in vitro (Fig 1B). Importantly, the eutB mutation is nonpolar as this mutant can respond to ethanolamine (Fig 1C). Subsequently, we performed competitive infections in which streptomycin-treated mice were orally infected with an equal mixture of wild type (WT) and ΔeutB (ΔeutB::CmR) strains or the WT and ΔeutR (ΔeutR::CmR) strains. S. Typhimurium infection presents as intestinal outgrowth, invasion of epithelial cells, and subsequent uptake by macrophages and dissemination to secondary lymphoid tissue. Therefore, to monitor the course of S. Typhimurium infection, we analyzed the number of recovered bacteria from the intestinal contents, the colon, and the spleen. At 2 and 4 days post infection (dpi), the ΔeutR and ΔeutB strains were significantly outcompeted by the WT strain in intestinal contents (Fig 1D and 1E). These data underscore the importance of ethanolamine metabolism in S. Typhimurium colonization of the intestinal tract, and these findings are consistent with previous work by Thiennimitr et al., who showed that ethanolamine metabolism provides a growth advantage to S. Typhimurium during intestinal colonization [17].

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