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*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

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 pectolyticmicro-organisms such as Pectobacterium atrosepticum via pectin and hemicellulose degrading enzymes. However, not all plantassociated microbes encode cell-wall-degrading enzymes, yet can metabolize l-arabinose, raising questions about their useof and access to the glycan in plants. Therefore, we examined l-arabinose metabolism in the food-borne pathogen Escherichiacoli O157:H7 (isolate Sakai) during its colonization of plants. l-arabinose metabolism (araBA) and transport (araF) genes wereactivated at 18°C in vitro by l-arabinose and expressed over prolonged periods in planta. Although deletion of araBAD did notimpact 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 oligosaccharidesinduced 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 aragene organization, transport and regulation from the related pectinolytic species P. atrosepticum, reflective of distinct plantassociated lifestyles.
Original languageEnglish
Article number001070
JournalMicrobiology
Volume167
Issue number7
DOIs
Publication statusPrint publication - 28 Jul 2021

Keywords

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

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