The role of l-arabinose metabolism for Escherichia coli O157:H7 in edible plants.

Arabinose is a major plant aldopentose in the form of arabinans complexed in cell wall polysaccharides or glycoproteins (AGP), but comparatively rare as a monosaccharide. l-arabinose is an important bacterial metabolite, accessed by pectolytic micro-organisms such as Pectobacterium atrosepticum via pectin and hemicellulose degrading enzymes. However, not all plant-associated microbes encode cell-wall-degrading enzymes, yet can metabolize l-arabinose, raising questions about their use of and access to the glycan in plants. Therefore, we examined l-arabinose metabolism in the food-borne pathogen Escherichia coli O157:H7 (isolate Sakai) during its colonization of plants. l-arabinose metabolism (araBA) and transport (araF) genes were activated at 18 °C in vitro by l-arabinose and expressed over prolonged periods in planta. Although deletion of araBAD did not impact the colonization ability of E. coli O157:H7 (Sakai) on spinach and lettuce plants (both associated with STEC outbreaks), araA was induced on exposure to spinach cell-wall polysaccharides. Furthermore, debranched and arabinan oligosaccharides induced ara metabolism gene expression in vitro, and stimulated modest proliferation, while immobilized pectin did not. Thus, E. coli O157:H7 (Sakai) can utilize pectin/AGP-derived l-arabinose as a metabolite. Furthermore, it differs fundamentally in ara gene organization, transport and regulation from the related pectinolytic species P. atrosepticum, reflective of distinct plant-associated lifestyles.

Escherichia coli O157:H7 transcriptome datasets for comparison of RNA-seq and microarray platforms.

Whole transcriptome analysis to investigate differential gene expression and regulatory adaption can be carried out on two different technological platforms: by probe hybridisation to microarrays or by RNAseq for deep sequencing. Since there are difference in terms of their genome coverage, sensitivity and cost, there is a requirement for robust comparisons to determine the platform of choice. Here, we present datasets for the whole transcriptional response verocytoxigenic Escherichia coli (VTEC) obtained from RNA-seq and microarray platforms in response to spinach, together with a comparison between the datasets (available at Array Express: E-MTAB-3249, E-MTAB-4120, E-MTAB-7441).

Differences in internalization and growth of Escherichia coli O157:H7 within the apoplast of edible plants, spinach and lettuce, compared with the model species Nicotiana benthamiana.

Internalization of food-borne bacteria into edible parts of fresh produce plants represents a serious health risk. Therefore, internalization of verocytotoxigenic E. coli O157:H7 isolate Sakai was assessed in two species associated with outbreaks, spinach (Spinacia oleracea) and lettuce (Lactuca sativa) and compared to the model species Nicotiana benthamiana. Internalization occurred in the leaves and roots of spinach and lettuce throughout a 10 day time-course. The plant species, tissue type and inoculum dose all impacted the outcome. A combination of low inoculum dose (~102 CFU) together with light microscopy imaging highlighted marked differences in the fate of endophytic E. coli O157:H7 Sakai. In the fresh produce species, bacterial growth was restricted but viable cells persisted over 20 days, whereas there was > 400-fold (~2.5 Log10 ) increase in growth in N. benthamiana. Colony formation occurred adjacent to epidermal cells and mesophyll cells or close to vascular bundles of N. benthamiana and contained components of a biofilm matrix, including curli expression and elicitation, extracellular DNA and a limited presence of cellulose. Together the data show that internalization is a relevant issue in crop production and that crop species and tissue need to be considered as food safety risk parameters.

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

[This corrects the article on p. 1088 in vol. 7, PMID: 27462311.].

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

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.

Diabetic foot-related problems: improving outcomes in the dialysis population using a foot assessment screening tri-algorithm (FAST).

A comprehensive literature review was conducted to determine the effect of diabetic foot checks on patient awareness, satisfaction, and outcomes. An algorithm was developed based on evidence-based practice, best practice guidelines, and current literature that can be used by nurses and medical staff in the management of foot-related problems in patients with diabetes on dialysis. An educational resource guide was also developed for use when education is required for foot-related problems.