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Title: Complexity and population regulation in unicellular algal cultures of Tetraselmis : an insight into individual and social interactions
Author: Arora , Mani
ISNI:       0000 0004 2741 246X
Awarding Body: University of Newcastle Upon Tyne
Current Institution: University of Newcastle upon Tyne
Date of Award: 2011
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"I would put my money on one fundamental principle ... all life evolves by the differential survival of replicating entities" (Richard Dawkins) This study is aimed towards understanding the complexity in unicellular eukaryotic phytoplankton populations. For my research work I have chosen Tetraselmis (Prasinophyceae) as the test organism. Prasinophycean algae are considered as ancestors of all green algae and embryophytic land plants. Tetraselmis is a key transition organism in the phylogeny of green algae. The taxonomy and phylogeny of the genus was investigated using morphological, ultrastructural, flow cytometry and molecular cladistics analysis. Partial 18s rDNA sequences from fresh material and from gene bank were analysed. In this process a new species of Tetraselmis (T. indica) from salt pans of Goa, India has been reported. The high structural and molecular divergence observed in this species pointed towards the evolution in function, hence, T. indica was chosen as the test organism. T. indica inhabits the highly dynamic salt pan ecosystem and survives in wide fluctuations of salinity and environmental parameters. Studies at cellular level, where changes in cell physiology, biochemistry and optical properties were studied as a means of evaluating their function and response to alteration in the environment were carried out. Experiments suggested the existence of structural, physiological and metabolic differentiation in Tetraselmis as indicated by flow cytometric studies, differential absorption spectras and staining patterns. Further it was observed that an incipient differentiation exists in otherwise identical cells giving rise to a heterogenous population whose components exhibit differential survival and behaviour, which work in association for the existence of population. Investigation of the biology of a single cell and its lineage helped in deciphering the consequences and implications of heterogeneity and complexity in this unicellular eukaryote. To study how component cells of a heterogenous population achieve their own behaviour, the hierarchy of subcomponents within these component cells was explored. Studies suggested that the fate of different components is set at a very early stage of cell division and hence the division products of a single cell exhibit ultrastructural and metabolic differences. To consider the social interactions, naturally associated bacteria were inoculated with the axenic cultures of cells and the differential and marked influence of each bacterium on its growth dynamics was observed. This study highlights that interrogating the complete web of individual and social interactions is of importance in understanding the functionality and regulation of unicellular life.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available