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Available from: Shreya Wani
[Show abstract] [Hide abstract] ABSTRACT: 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.
Available from: Zhenying Wang
[Show abstract] [Hide abstract] ABSTRACT: The full-length cDNA of four Ofapn aminopeptidases were cloned and sequenced from susceptible and resistant Ostrinia furnacalis strains. Four sequences were identified as APN because they shared the common structural features with APN from Lepidoptera, including the signal peptide, GPI anchor signal, the zinc binding/gluzincin motif HEX2HX18E and the gluzincin aminopeptidase motif GAMEN. Compared with APN sequences from the susceptible strain, there were 9, 5, 10 and 12 amino acid variations in the deduced protein sequences from the resistant strain. There were also differences in mRNA expression of the four Ofapn genes between resistant and susceptible O. furnacalis strains.
Available from: Graham C Smith
[Show abstract] [Hide abstract] ABSTRACT: American Foulbrood (AFB) caused by Paenibacillus larvae is the most damaging bacterial brood disease of the honey bee (Apis mellifera), causing colony deaths on all continents where honey bees are managed. AFB has been a persistent problem in the UK for over 70 years, with a fluctuating number of cases discovered annually. Once diseased colonies are identified, they are destroyed to reduce pathogen spread. We investigated the pattern of AFB cases recorded over the period 1994 to 2012 using spatial statistical approaches with a view to identifying the nature of spread across England and Wales. Our results indicated that AFB exhibits significant spatial aggregation at distances from 10-30 km with aggregations lasting between 1 and 5 year periods. Kernel smoothing indicated areas of elevated relative risk in different years and these were further detailed by spatial scan statistics. We identified disease clusters and successfully estimated their size, location and duration. The majority of clusters did not persist in all years indicating that management measures may lead to localised extinction of the disease. Whilst less common, persistent clusters likely indicate potential endemic or exotic risk points. The application of robust epidemiological approaches to improve the control of AFB are discussed.
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