Stress induced evolution of non-genotypic heterogeneity

Moreton, Katy V. (2017) Stress induced evolution of non-genotypic heterogeneity. MRes thesis, University of Nottingham.

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Genetically identical populations can exhibit a range of behaviours within a phenotype, despite sharing a genetic background. This is referred to as non- genotypic heterogeneity (NGH). NGH can be conferred by a heritable change in DNA that affects the noise surrounding expression of a protein product. Copper and zinc are trace metals that are essential for normal growth and development, but are toxic in surplus amounts. NGH in response to copper stress has previously been identified in wild yeast isolates, but this was not produced under standardised conditions. Can we reproduce the conditions from the environment to produce high NGH through a controlled experimental evolution?

Batch style evolution at 18°C occurred for ≥ 600 generations under three conditions (no stress, 6 mM copper nitrate stress, or 1 mM zinc chloride stress). Evolution under metal stress produced strains with increased metal resistance. Increased NGH is suggested to evolve in response to copper nitrate exposure, but not in response to zinc chloride exposure, though this change is not reproducable after a further 20 generations in the absense of stress. Flow cytometric determination of variation in Phloxine B staining under stress (a measure of cell vitality), revealed a) an increase in variation in absorbance among cells in cells evolved with copper stress compared to those that were not, and b) cell size variation showed no change. Colony size variation increased when cells were evolved with copper nitrate, driven by the appearance of large and small colony subpopulations. This change is not indefinitely stable, only remaining for around 30 generations. Small colonies may provide a fitness benefit to the population as a whole. Whole genome sequencing will reveal any SNP changes responsible for the phenotypes observed.

Item Type: Thesis (University of Nottingham only) (MRes)
Supervisors: Avery, Simon V.
MacColl, Andrew
Subjects: Q Science > QK Botany > QK504 Cryprogams
Faculties/Schools: UK Campuses > Faculty of Medicine and Health Sciences > School of Life Sciences
Item ID: 43753
Depositing User: Moreton, Katy
Date Deposited: 01 Nov 2017 14:59
Last Modified: 13 Dec 2017 05:56

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