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Whole-Transcriptome Analysis of Verocytotoxigenic Escherichia coli O157:H7 (Sakai) Suggests Plant-Species-Specific Metabolic Responses on Exposure to Spinach and Lettuce Extracts.

Crozier L, Hedley PE, Morris J, Wagstaff C, Andrews SC, Toth I, Jackson RW, Holden NJ - Front Microbiol (2016)

Bottom Line: Plant extracts were used to reduce heterogeneity inherent in plant-microbe interactions and remove the effect of plant immunity.Induction of stress-response genes reflected the apparent physiological status of the bacterial genes in each extract, as a result of glutamate-dependent acid resistance, nutrient stress, or translational stalling.A large proportion of differentially regulated genes are uncharacterized (annotated as hypothetical), which could indicate yet to be described functional roles associated with plant interaction for E. coli O157:H7 Sakai.

View Article: PubMed Central - PubMed

Affiliation: Cell and Molecular Sciences, The James Hutton Institute Dundee, UK.

ABSTRACT
Verocytotoxigenic Escherichia coli (VTEC) can contaminate crop plants, potentially using them as secondary hosts, which can lead to food-borne infection. Currently, little is known about the influence of the specific plant species on the success of bacterial colonization. As such, we compared the ability of the VTEC strain, E. coli O157:H7 'Sakai,' to colonize the roots and leaves of four leafy vegetables: spinach (Spinacia oleracea), lettuce (Lactuca sativa), vining green pea (Pisum sativum), and prickly lettuce (Lactuca serriola), a wild relative of domesticated lettuce. Also, to determine the drivers of the initial response on interaction with plant tissue, the whole transcriptome of E. coli O157:H7 Sakai was analyzed following exposure to plant extracts of varying complexity (spinach leaf lysates or root exudates, and leaf cell wall polysaccharides from spinach or lettuce). Plant extracts were used to reduce heterogeneity inherent in plant-microbe interactions and remove the effect of plant immunity. This dual approach provided information on the initial adaptive response of E. coli O157:H7 Sakai to the plant environment together with the influence of the living plant during bacterial establishment and colonization. Results showed that both the plant tissue type and the plant species strongly influence the short-term (1 h) transcriptional response to extracts as well as longer-term (10 days) plant colonization or persistence. We show that propagation temperature (37 vs. 18°C) has a major impact on the expression profile and therefore pre-adaptation of bacteria to a plant-relevant temperature is necessary to avoid misleading temperature-dependent wholescale gene-expression changes in response to plant material. For each of the plant extracts tested, the largest group of (annotated) differentially regulated genes were associated with metabolism. However, large-scale differences in the metabolic and biosynthetic pathways between treatment types indicate specificity in substrate utilization. Induction of stress-response genes reflected the apparent physiological status of the bacterial genes in each extract, as a result of glutamate-dependent acid resistance, nutrient stress, or translational stalling. A large proportion of differentially regulated genes are uncharacterized (annotated as hypothetical), which could indicate yet to be described functional roles associated with plant interaction for E. coli O157:H7 Sakai.

No MeSH data available.


Related in: MedlinePlus

Flagella-curli regulatory network gene expression profiles. Expression data for selected E. coli O157:H7 (Sakai) genes in response to different plant extracts was overlaid onto the network to generate a color code of expression: orange for induction, blue for repression, and white for no change < ± twofold. Expression is provided for selected genes that were affected in at least one of the four plant extracts. Gene names are in italics; genes associated with a phenotype are grouped together; an overall approximate change (indicated by ‘∼’) is provided for flagella genes (data in Supplementary Table S2B). The data for all four conditions is arranged in a grid, ordered as indicated in the Key: LL, leaf lysates and RE, root exudates for spinach; Spin_PS, spinach CWPSs; Lett_PS, lettuce CWPSs. Regulatory connections, both direct and indirect (Pesavento et al., 2008; Pesavento and Hengge, 2012; Guttenplan and Kearns, 2013), with either positive (black arrow) or inhibitory (red bar) effects are shown.
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Figure 5: Flagella-curli regulatory network gene expression profiles. Expression data for selected E. coli O157:H7 (Sakai) genes in response to different plant extracts was overlaid onto the network to generate a color code of expression: orange for induction, blue for repression, and white for no change < ± twofold. Expression is provided for selected genes that were affected in at least one of the four plant extracts. Gene names are in italics; genes associated with a phenotype are grouped together; an overall approximate change (indicated by ‘∼’) is provided for flagella genes (data in Supplementary Table S2B). The data for all four conditions is arranged in a grid, ordered as indicated in the Key: LL, leaf lysates and RE, root exudates for spinach; Spin_PS, spinach CWPSs; Lett_PS, lettuce CWPSs. Regulatory connections, both direct and indirect (Pesavento et al., 2008; Pesavento and Hengge, 2012; Guttenplan and Kearns, 2013), with either positive (black arrow) or inhibitory (red bar) effects are shown.

Mentions: Gene associated with motility and biofilm formation are often associated with successful colonization of plants (Cooley et al., 2003; Van Houdt and Michiels, 2010). Both groups were strongly repressed in the baseline condition of growth in minimal medium at 18°C compared to 37°C, as indicated above. However, upon exposure to spinach whole-leaf lysates or root exudates, the genes encoding the master motility regulator FlhDC were repressed 7–28-fold, but were induced 23- and 52-fold (respectively) on exposure to lettuce CWPS (Figure 5). In lettuce CWPS, this increase in motility-gene regulator expression was coupled with repression of the biofilm-related gene, ECs2085 (bdm; 50–55-fold repressed) encoding the biofilm-dependent modulation protein, and a modest effect on the genes encoding curli fibers (csgA,B: both threefold). In contrast, curli genes were induced on exposure to spinach root exudates (also by threefold; Supplementary Table S1), indicative of a switch between sessility vs. motility. Some of the genes encoding fimbriae were induced, but only to moderate levels. For example, multiple signals for loc2 were induced in response to root exudates, including ECs0142 (yadM, a putative structural subunit) and yadK (also a structural subunit), by 2- and 3-fold, respectively.


Whole-Transcriptome Analysis of Verocytotoxigenic Escherichia coli O157:H7 (Sakai) Suggests Plant-Species-Specific Metabolic Responses on Exposure to Spinach and Lettuce Extracts.

Crozier L, Hedley PE, Morris J, Wagstaff C, Andrews SC, Toth I, Jackson RW, Holden NJ - Front Microbiol (2016)

Flagella-curli regulatory network gene expression profiles. Expression data for selected E. coli O157:H7 (Sakai) genes in response to different plant extracts was overlaid onto the network to generate a color code of expression: orange for induction, blue for repression, and white for no change < ± twofold. Expression is provided for selected genes that were affected in at least one of the four plant extracts. Gene names are in italics; genes associated with a phenotype are grouped together; an overall approximate change (indicated by ‘∼’) is provided for flagella genes (data in Supplementary Table S2B). The data for all four conditions is arranged in a grid, ordered as indicated in the Key: LL, leaf lysates and RE, root exudates for spinach; Spin_PS, spinach CWPSs; Lett_PS, lettuce CWPSs. Regulatory connections, both direct and indirect (Pesavento et al., 2008; Pesavento and Hengge, 2012; Guttenplan and Kearns, 2013), with either positive (black arrow) or inhibitory (red bar) effects are shown.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4940412&req=5

Figure 5: Flagella-curli regulatory network gene expression profiles. Expression data for selected E. coli O157:H7 (Sakai) genes in response to different plant extracts was overlaid onto the network to generate a color code of expression: orange for induction, blue for repression, and white for no change < ± twofold. Expression is provided for selected genes that were affected in at least one of the four plant extracts. Gene names are in italics; genes associated with a phenotype are grouped together; an overall approximate change (indicated by ‘∼’) is provided for flagella genes (data in Supplementary Table S2B). The data for all four conditions is arranged in a grid, ordered as indicated in the Key: LL, leaf lysates and RE, root exudates for spinach; Spin_PS, spinach CWPSs; Lett_PS, lettuce CWPSs. Regulatory connections, both direct and indirect (Pesavento et al., 2008; Pesavento and Hengge, 2012; Guttenplan and Kearns, 2013), with either positive (black arrow) or inhibitory (red bar) effects are shown.
Mentions: Gene associated with motility and biofilm formation are often associated with successful colonization of plants (Cooley et al., 2003; Van Houdt and Michiels, 2010). Both groups were strongly repressed in the baseline condition of growth in minimal medium at 18°C compared to 37°C, as indicated above. However, upon exposure to spinach whole-leaf lysates or root exudates, the genes encoding the master motility regulator FlhDC were repressed 7–28-fold, but were induced 23- and 52-fold (respectively) on exposure to lettuce CWPS (Figure 5). In lettuce CWPS, this increase in motility-gene regulator expression was coupled with repression of the biofilm-related gene, ECs2085 (bdm; 50–55-fold repressed) encoding the biofilm-dependent modulation protein, and a modest effect on the genes encoding curli fibers (csgA,B: both threefold). In contrast, curli genes were induced on exposure to spinach root exudates (also by threefold; Supplementary Table S1), indicative of a switch between sessility vs. motility. Some of the genes encoding fimbriae were induced, but only to moderate levels. For example, multiple signals for loc2 were induced in response to root exudates, including ECs0142 (yadM, a putative structural subunit) and yadK (also a structural subunit), by 2- and 3-fold, respectively.

Bottom Line: Plant extracts were used to reduce heterogeneity inherent in plant-microbe interactions and remove the effect of plant immunity.Induction of stress-response genes reflected the apparent physiological status of the bacterial genes in each extract, as a result of glutamate-dependent acid resistance, nutrient stress, or translational stalling.A large proportion of differentially regulated genes are uncharacterized (annotated as hypothetical), which could indicate yet to be described functional roles associated with plant interaction for E. coli O157:H7 Sakai.

View Article: PubMed Central - PubMed

Affiliation: Cell and Molecular Sciences, The James Hutton Institute Dundee, UK.

ABSTRACT
Verocytotoxigenic Escherichia coli (VTEC) can contaminate crop plants, potentially using them as secondary hosts, which can lead to food-borne infection. Currently, little is known about the influence of the specific plant species on the success of bacterial colonization. As such, we compared the ability of the VTEC strain, E. coli O157:H7 'Sakai,' to colonize the roots and leaves of four leafy vegetables: spinach (Spinacia oleracea), lettuce (Lactuca sativa), vining green pea (Pisum sativum), and prickly lettuce (Lactuca serriola), a wild relative of domesticated lettuce. Also, to determine the drivers of the initial response on interaction with plant tissue, the whole transcriptome of E. coli O157:H7 Sakai was analyzed following exposure to plant extracts of varying complexity (spinach leaf lysates or root exudates, and leaf cell wall polysaccharides from spinach or lettuce). Plant extracts were used to reduce heterogeneity inherent in plant-microbe interactions and remove the effect of plant immunity. This dual approach provided information on the initial adaptive response of E. coli O157:H7 Sakai to the plant environment together with the influence of the living plant during bacterial establishment and colonization. Results showed that both the plant tissue type and the plant species strongly influence the short-term (1 h) transcriptional response to extracts as well as longer-term (10 days) plant colonization or persistence. We show that propagation temperature (37 vs. 18°C) has a major impact on the expression profile and therefore pre-adaptation of bacteria to a plant-relevant temperature is necessary to avoid misleading temperature-dependent wholescale gene-expression changes in response to plant material. For each of the plant extracts tested, the largest group of (annotated) differentially regulated genes were associated with metabolism. However, large-scale differences in the metabolic and biosynthetic pathways between treatment types indicate specificity in substrate utilization. Induction of stress-response genes reflected the apparent physiological status of the bacterial genes in each extract, as a result of glutamate-dependent acid resistance, nutrient stress, or translational stalling. A large proportion of differentially regulated genes are uncharacterized (annotated as hypothetical), which could indicate yet to be described functional roles associated with plant interaction for E. coli O157:H7 Sakai.

No MeSH data available.


Related in: MedlinePlus