The role of bacteria in paralytic shellfish poisoning

Hold, Georgina Louise (1999) The role of bacteria in paralytic shellfish poisoning. PhD thesis, University of Glasgow.

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Abstract

Historically the production of paralytic shellfish toxins (PST), has been attributed to dinoflagellates. However, in the last decade, increasing evidence has been presented to indicate the involvement of a wide range of bacterial species including cyanobacteria and heterotrophic bacteria (Gallacher et al., 1997). Several studies investigating bacteria capable of PST production, have identified bacteria associated with dinoflagellates are capable of autonomous PST production (Gallacher et al., 1997). However, more recent research has focussed on the effects of these bacteria on toxin production by dinoflagellates, for which the production of bacterial-free (axenic) cultures is essential to identify whether dinoflagellates are capable of autonomous toxin production, in the absence of bacteria. Many different methods to produce axenic algal cultures have been published, including washing methods and the addition of bacteriolytic compounds. However, efforts to generate axenic dinoflagellate cultures, have been hampered not only by difficulties in removing associated bacteria, but also by the lack of effective methods for assessing the presence of certain bacteria. Traditionally, the absence of bacterial growth on marine media was considered acceptable proof for axenic status. However, as the numbers of bacteria determined by culture methods falls short of numbers detected using microscopy (Akagi et al., 1977), culture methods alone have been deemed inadequate to determine the axenic status of algal cultures. In this study, the production of an axenic dinoflagellate culture was vital, firstly, to assess the effect on dinoflagellate toxin production following removal of all associated bacteria, and secondly, to identify whether original toxicity was restored when the microflora was replaced. Methods to assess the axenic nature of cultures combined traditional methods of culturing, with epifluorescence microscopy, the method now frequently relied upon for axenic confirmation. However, molecular techniques were also included, which allowed the axenic status of dinoflagellate cultures to be confidently determined. The availability of molecular techniques also enabled an assessment of the bacterial diversity associated with original dinoflagellate cultures to be conducted, with culture-based and non culture-based identification systems adopted. This investigation indicated that a diverse range of bacteria were associated with cultures, although discrepancies between the two detection methods were noted. Results from the assessment of axenic dinoflagellate cultures confirmed the need for molecular methods, as bacterial DNA was identified in cultures which were considered axenic cultures using media assessment and epifluorescence microscopy. (Abstract shortened by ProQuest.).

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Additional Information: Adviser: S Gallacher
Keywords: Microbiology, Toxicology
Date of Award: 1999
Depositing User: Enlighten Team
Unique ID: glathesis:1999-71587
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 10 May 2019 14:11
Last Modified: 10 May 2019 14:11
URI: http://theses.gla.ac.uk/id/eprint/71587

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