Dataset Information

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

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.

SUBMITTER: Crozier L

PROVIDER: S-EPMC4940412 | biostudies-literature | 2016

REPOSITORIES: biostudies-literature

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Publications

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

Crozier Louise L Hedley Pete E PE Morris Jenny J Wagstaff Carol C Andrews Simon C SC Toth Ian I Jackson Robert W RW Holden Nicola J NJ

Frontiers in microbiology 20160712

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), a ...[more]

PMID: 27462311

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Project description:Food-borne illness arising for Shiga-toxigenic Escherichia coli is often linked to consumption of fruit and vegetables as the bacteria have the ability to interact with plants and use them as alternative or secondary hosts. Attachment of the bacteria to host tissue is one of the first steps in the interaction, and, as with mammalian hosts, has shown to be mediated by a combination of non-specific and specific adhesin-mediated interactions. We took a high-throughput positive-selection approach to investigate adherence mechanisms for E. coli O157:H7 isolate Sakai by inoculating a BAC clone library onto spinach, which was quantified by microarray hybridisation and gene loci enrichment measured using a Bayesian hierarchical model. The screen involved four successive rounds of adherence to spinach roots, resulting in 115 CDS credible candidates, covered by seven contiguous genomic regions. Two candidates regions selected for functional assessment included a chaperone-usher fimbrial gene cluster (loc6) and the type two secretion system (T2SS). The TS22 was found to significantly enhance binding to spinach roots and leaves, demonstrated with a BAC-T2SS clone and by mutagenesis of the secretin protein, EtpD. Both etpD and the inner membrane anchor protein gene etpC were expressed at 18 degree celsius, and expression of etpD was demonstrated for STEC (Sakai) resident in the apoplastic spaces in spinach leaf tissue. Together, these data indicate a novel function for STEC T2SS in adherence to plant tissue. Experiment 1: screening E coli O157:H7 Sakai genes for adherence to spinach roots. A BAC library of Sakai clones in an E coli DH10B background (which has poor root adherence) defined as the 'Input pool', was incubated with spinach roots for 4 rounds of enrichment, defined as the 'Output pool'. Control samples (defined as 'Input control' & 'Output control') were cultures of pV41 vector only. DNA extractions from test pools were labelled with Cy3 throughout. DH10B DNA was used for grid alignment and labelled with Cy5 throughout.

Dataset Information

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

Publications

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

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