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

Louise Crozier, Jacqueline Marshall, Ashleigh Holmes, Kathryn Mary Wright, Yannick Rossez, Bernhard Merget, Sonia Humphris, Ian Toth, Robert Wilson Jackson, Nicola Jean Holden (Lead / Corresponding author)

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Abstract

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.

Original languageEnglish
Article number001070
Number of pages12
JournalMicrobiology
Volume167
Issue number7
Early online date28 Jul 2021
DOIs
Publication statusPublished - 2021

Keywords

  • Bacterial pathogens
  • Food safety
  • Plant cell wall degrading enzymes
  • Plant-microbe interactions
  • Vegetables

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