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A novel application of non-invasive microelectrode ion flux measuring technique in food microbiology

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Shabala, SI 2002 , 'A novel application of non-invasive microelectrode ion flux measuring technique in food microbiology', PhD thesis, University of Tasmania.

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Abstract

At present, both the control of bacterial growth to ensure food safety, and the balancing of nutritional requirements and optimization of culture growth conditions for beneficial food microorganisms, are essentially empirically based. An alternative time- and money-saving approach to this implies a better understanding of the physiological processes underlying the cellular response to the applied treatment. In the present work, the non invasive microelectrode ion flux measuring technique (MIFE®) was first introduced in food microbiology, to address some of the above issues and to shed some light on adaptive responses of bacterial and fungal cells to environmental change.
Several "case studies" were undertaken to explore the utility of the MIFE technique to study of adaptive responses in a variety of microorganisms.
First, various methodological aspects of ion-flux measurements in microorganisms were addressed. These included the issue of cell immobilisation, specific details of culture growth and preparation, and potentially confounding effects of environmental "hurdles" on measuring electrodes such as ionic strength of solution, pH etc.
Second, a marine protist thraustochytrid ACEM C, proposed as a valuable single source of polyunsaturated fatty acids, was used to demonstrate the applicability of the MIFE technique to understanding the physiology of growth and adaptive responses at the single cell level. Various aspects of membrane-transport processes, associated with thraustochytrid cell growth and development, as well as its adaptive responses to osmoticurn, temperature, and nutritional status, were studied.
Third, in a pioneering application of the MIFE technique to bacterial cells, adaptive responses of immobilised bacteria of different genera were studied at the population level. The major emphasis was on Listeria monocytogenes and Escherichia coli, two physiologically contrasting organisms of great economic importance to food microbiology. The adaptive responses were studied in relation to acid stress, bacteriocin (nisin) action, and substrate availability.
Finally, an investigation was made into the feasibility and utility of combining the MIFE technique with another method and study of bacterial adaptive responses, specifically, fluorescence Ratio Imaging Microscopy (FRIM), L. monocytogenes responses to acid stress were used as a case study.
Overall, this study showed, for the first time, that the application of the MIFE technique to study membrane-transport processes in food-related rilicroorganisms might lead to significant conceptual advances in the understanding of the mechanisms underlying growth and adaptive responses of bacterial and fungal cells and could contribute to reducing food-borne infections or towards improved productions of nutritionally important compounds.

Item Type: Thesis - PhD
Authors/Creators:Shabala, SI
Keywords: Food
Copyright Information:

Copyright 2002 the author - The University is continuing to endeavour to trace the copyright owner(s) and in the meantime this item has been reproduced here in good faith. We would be pleased to hear from the copyright owner(s).

Additional Information:

Thesis (PhD)--University of Tasmania, 2002. Includes bibliographical references

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