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Interactions between leaf lesions and the phyllosphere microbiota in leafy vegetables

Mulaosmanovic, Emina (2021). Interactions between leaf lesions and the phyllosphere microbiota in leafy vegetables. Diss. (sammanfattning/summary) Sveriges lantbruksuniv., Acta Universitatis Agriculturae Sueciae, 1652-6880
ISBN 978-91-7760-716-8
eISBN 978-91-7760-717-5
[Doctoral thesis]

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Abstract

Leafy vegetables (baby leaves) are considered an important source and vector for transmission of foodborne pathogens to humans. Contamination can occur from farm to fork. Although ‘rare’, contamination events have a substantial impact on public health. The shigatoxigenic bacterium, Escherichia coli O157:H7, can establish on the surface (epiphyte) and interior (endophyte) of leaves. Natural openings and leaf lesions serve as entry points, and internalised bacterial cells are shielded from rinse water and sanitisers. In this thesis, a new method for scrutinising leaf lesions in leafy vegetables was developed and used to link leaf damage to the dynamics of E. coli O157:H7gfp+ and the indigenous microbiota in the phyllosphere, and to evaluate use of calcium fortification of leafy vegetables for damage reduction. The new approach combines trypan blue dye staining of whole leaves with digital image analysis for detection and automated quantification of damage, enabling assessment of lesion size, shape and position. Number of lesions and relative lesion area were found to be crop-specific and increased along the production chain, while diversity of the leaf-associated microbial community decreased upon entry of baby leaves to the cold chain. The size of individual lesions and damaged leaf area affected the depth of invasion into plant tissue, dispersal to adjacent areas and number of culturable E. coli O157:H7gfp+ directly after inoculation. However, differences in culturable E. coli O157:H7gfp+ retrieved from leaf macerate evened out after 2 days post-inoculation (dpi). Leaf spraying with calcium decreased the number of lesions and damaged area on spinach leaves, lowering log CFU E. coli cm-2 detached at 0 and 1 dpi. Overall, the results in this thesis question the assumption that macroscopically intact leaves are free of lesions and safe. The method developed can assist in establishment of hurdles for preventing transmission of foodborne pathogens via baby leaves.

Authors/Creators:Mulaosmanovic, Emina
Title:Interactions between leaf lesions and the phyllosphere microbiota in leafy vegetables
Series Name/Journal:Acta Universitatis Agriculturae Sueciae
Year of publishing :2021
Number:2021:19
Number of Pages:100
Publisher:Department of Biosystems and Technology, Swedish University of Agricultural Sciences
ISBN for printed version:978-91-7760-716-8
ISBN for electronic version:978-91-7760-717-5
ISSN:1652-6880
Language:English
Publication Type:Doctoral thesis
Article category:Other scientific
Version:Published version
Full Text Status:Public
Subjects:(A) Swedish standard research categories 2011 > 1 Natural sciences > 106 Biological Sciences (Medical to be 3 and Agricultural to be 4) > Microbiology (Microbiology in the medical area to be 30109)
(A) Swedish standard research categories 2011 > 4 Agricultural Sciences > 401 Agricultural, Forestry and Fisheries > Horticulture
(A) Swedish standard research categories 2011 > 4 Agricultural Sciences > 401 Agricultural, Forestry and Fisheries > Food Science
Keywords:calcium chloride, damage, E. coli O157:H7, Illumina, internalisation, microbial communities, metagenomics, phyllosphere, pre-harvest, post-harvest, spinach, Swiss chard, trypan blue
URN:NBN:urn:nbn:se:slu:epsilon-p-110885
Permanent URL:
http://urn.kb.se/resolve?urn=urn:nbn:se:slu:epsilon-p-110885
ID Code:22693
Faculty:LTV - Fakulteten för landskapsarkitektur, trädgårds- och växtproduktionsvetenskap
Department:(LTJ, LTV) > Department of Biosystems and Technology (from 130101)
Deposited By: SLUpub Connector
Deposited On:03 Mar 2021 11:23
Metadata Last Modified:03 Mar 2021 12:02

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