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The Quest for Characteristics Discriminating between Phaeocystis Strains

Bosma, H. (1996) The Quest for Characteristics Discriminating between Phaeocystis Strains. Master's Thesis / Essay, Biology.

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The aim of this project was to describe clonal similarities or dissimilarities of cultured Phaeocystis strains, in an attempt to clarify taxonomic confusion and methodological problems. The main obstacle in doing so was the change of composition of the sea water used during the course of the experiment which meant that obtained results could not be repeated. Three series of batch cultures were performed with five P. globosa-type strains originating from different sites in the North Sea. The strains were investigated on as many parameters as possible by performing culture-based and genetic studies. Autofluorescence of acetone extracted samples showed to be a good biomass estimation of colony forming Phaeocystis. Colony morphology had previously been used as a criterium for Phaeocystis taxonomy. In this study the shape and size of colonies varied daily and in every series of batch cultures. The strains could be distinguished visually during handling of the strains. It was demonstrated that percentage of cells in colonies was not a reliable criterium but the method was succesfully used. Cell sizes overlapped but have potential to discriminate between strains when used in combination with other taxonomic parameters. The ranges of the cell sizes fell into the ranges indicated in the literature. Growth rates of the strains differed for all the series of batch cultures of the same strain so it has not been used as a taxonomic parameter. Pigment analysis did not show high variation between the strains although pigments have previously been applied as chemotaxonomical markers for Phaeocystis taxonomy by several authors. This study indicates that on the level of strain discrimination pigment analysis is not sensitive enough. Sugar composition studies revealed that sugar patterns of strains were variable. Total sugar analysis showed an increase in amount of total sugars when nutrients were limiting. The filter method tested for the measurements of total sugar per cell was succesful. RAPD analysis allowed the strains to be grouped in two clusters corresponding with their geographical origin. The main conclusion emerged from this study is that inter-population variation is high in P. globosa strains. Cell size and sugar fingerprints have potential to discriminate between strains and the RAPD data revealed clear differences between the strains in accordance with their geographical origin.

Item Type: Thesis (Master's Thesis / Essay)
Degree programme: Biology
Thesis type: Master's Thesis / Essay
Language: English
Date Deposited: 15 Feb 2018 07:31
Last Modified: 15 Feb 2018 07:31

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