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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

Differentially expressed gene comparison by plant species and tissue. Overview of common and specific E. coli O157:H7 (Sakai) genes differentially expressed in plant extracts. The number of genes was compared in a Venn diagram of all four treatments (A) and for the spinach extracts only (B). Key: ‘Spin,’ spinach (S. olercera); ‘Lett,’ lettuce (L. sativa); ‘LL,’ leaf lysates; ‘RE,’ root exudates; ‘PS,’ cell wall polysaccharides (CWPSs). Images were generated using the Venny program (Oliveros, 2007).
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Figure 2: Differentially expressed gene comparison by plant species and tissue. Overview of common and specific E. coli O157:H7 (Sakai) genes differentially expressed in plant extracts. The number of genes was compared in a Venn diagram of all four treatments (A) and for the spinach extracts only (B). Key: ‘Spin,’ spinach (S. olercera); ‘Lett,’ lettuce (L. sativa); ‘LL,’ leaf lysates; ‘RE,’ root exudates; ‘PS,’ cell wall polysaccharides (CWPSs). Images were generated using the Venny program (Oliveros, 2007).

Mentions: Wholescale changes in E. coli O157:H7 (Sakai) gene expression occurred following 1 h of exposure to the different extracts at 18°C (Figure 1). Exposure to spinach leaf lysate resulted in differential expression of 27% of the Sakai genome, 745 genes were induced and 738 were repressed, while 35% of the Sakai genome was differentially expressed on exposure to spinach root exudates: 981 induced and 972 repressed. In general, there appeared to be an inverse correlation in differential gene expression between exposure to spinach root exudates and spinach leaf lysates (Figure 1). The response to leaf CWPSs was examined to exclude the effects of other leaf components (e.g., apoplastic fluid and intracellular contents). Gene expression for E. coli O157:H7 (Sakai) exposed to spinach and lettuce CWPS for 1 h showed marked differences between species, with 460 and 97 genes displaying differential expression in response to lettuce and spinach CWPS, respectively, when compared to the response to the negative, no-plant control (an extract prepared from vermiculite, the inert plant growth substrate; Figure 1). Thus, the extent of expression change was far less with the CWPS (average of 3.2%) than with the leaf and root samples (average of 13%), as anticipated. Comparison between the species or tissue types showed little commonality in differentially expressed genes (Figure 2). This is well-illustrated by the observations that only 13 genes were subject to regulation by all three spinach extracts, and only 23 of the 586 CWPS-regulated genes were also regulated by both the spinach and lettuce extracts.


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)

Differentially expressed gene comparison by plant species and tissue. Overview of common and specific E. coli O157:H7 (Sakai) genes differentially expressed in plant extracts. The number of genes was compared in a Venn diagram of all four treatments (A) and for the spinach extracts only (B). Key: ‘Spin,’ spinach (S. olercera); ‘Lett,’ lettuce (L. sativa); ‘LL,’ leaf lysates; ‘RE,’ root exudates; ‘PS,’ cell wall polysaccharides (CWPSs). Images were generated using the Venny program (Oliveros, 2007).
© Copyright Policy
Related In: Results  -  Collection

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

Figure 2: Differentially expressed gene comparison by plant species and tissue. Overview of common and specific E. coli O157:H7 (Sakai) genes differentially expressed in plant extracts. The number of genes was compared in a Venn diagram of all four treatments (A) and for the spinach extracts only (B). Key: ‘Spin,’ spinach (S. olercera); ‘Lett,’ lettuce (L. sativa); ‘LL,’ leaf lysates; ‘RE,’ root exudates; ‘PS,’ cell wall polysaccharides (CWPSs). Images were generated using the Venny program (Oliveros, 2007).
Mentions: Wholescale changes in E. coli O157:H7 (Sakai) gene expression occurred following 1 h of exposure to the different extracts at 18°C (Figure 1). Exposure to spinach leaf lysate resulted in differential expression of 27% of the Sakai genome, 745 genes were induced and 738 were repressed, while 35% of the Sakai genome was differentially expressed on exposure to spinach root exudates: 981 induced and 972 repressed. In general, there appeared to be an inverse correlation in differential gene expression between exposure to spinach root exudates and spinach leaf lysates (Figure 1). The response to leaf CWPSs was examined to exclude the effects of other leaf components (e.g., apoplastic fluid and intracellular contents). Gene expression for E. coli O157:H7 (Sakai) exposed to spinach and lettuce CWPS for 1 h showed marked differences between species, with 460 and 97 genes displaying differential expression in response to lettuce and spinach CWPS, respectively, when compared to the response to the negative, no-plant control (an extract prepared from vermiculite, the inert plant growth substrate; Figure 1). Thus, the extent of expression change was far less with the CWPS (average of 3.2%) than with the leaf and root samples (average of 13%), as anticipated. Comparison between the species or tissue types showed little commonality in differentially expressed genes (Figure 2). This is well-illustrated by the observations that only 13 genes were subject to regulation by all three spinach extracts, and only 23 of the 586 CWPS-regulated genes were also regulated by both the spinach and lettuce extracts.

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