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Investigation of potential reasons for bacterial survival on ‘ready-to-eat’ leafy produce during exposure to gaseous ozone

Wani, Shreya; Barnes, Jeremy; Singleton, Ian


Shreya Wani

Jeremy Barnes


Fresh leafy produce, such as lettuce and coriander, are subject to post-harvest microbial contamination and decay. Because of increasing pesticide resistance and consumer pressures, alternative residue-free treatments, such as ozone, are being actively explored and encouraged to reduce microbial loads and curb spoilage of crops in storage/transit. However, several researchers have reported that a component of the bacterial population on leaf surfaces is resistant to ozone treatment. To investigate the potential reasons for this bacterial survival, confocal microscopy was used to visualise microbes on leaf surfaces before and after ozone treatment. Direct observation (live/dead cell staining) of cells after ozone exposure showed that some cells were still alive; this included cells in small colonies as well as individual cells. We hypothesised that cell (colony) age and prior stress (cold) contributes to, or is responsible for, the ozone resistance observed. Interestingly, cells derived from older agar-grown colonies (7–12-day-old) and cold stressed cells of a Pseudomonas sp. (isolated from coriander) showed higher ozone resistance than that of control cells (4-day-old colonies). These findings suggest that a range of factors are responsible for ozone resistance and further work to improve our understanding of the mechanisms of ozone resistance may lead to improved methods to reduce microbial spoilage of fresh produce.


Wani, S., Barnes, J., & Singleton, I. (2016). Investigation of potential reasons for bacterial survival on ‘ready-to-eat’ leafy produce during exposure to gaseous ozone. Postharvest Biology and Technology, 111, 185-190.

Journal Article Type Article
Acceptance Date Aug 13, 2015
Online Publication Date Aug 30, 2015
Publication Date 2016-01
Deposit Date Jan 13, 2016
Publicly Available Date Mar 1, 2017
Journal Postharvest Biology and Technology
Print ISSN 0925-5214
Publisher Elsevier
Peer Reviewed Peer Reviewed
Volume 111
Pages 185-190
Keywords Fresh produce; Ozone resistance; Confocal microscopy;
Pseudomonas sp.; Spoilage; ozone gas;
Public URL
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