Vitamin B12-mediated physiology, mutualisms, and gene regulation studies in Chlamydomonas reinhardtii and Phaeodactylum tricornutum
type: CreativeWork
description: Many organisms engage in symbiotic relationships that govern, to varying degrees, the function of ecosystems and their evolutionary history. It is important to understand the origins and dynamics of these systems. Especially important is the aquatic ecosystem, which is essential for approximately 50% of global primary production, and where many photosynthetic algae participate in symbiosis with bacteria where the latter provide vitamins such as cobalamin (vitamin B12) in exchange for fixed carbon from the algae. Vitamin B12 is used as a cofactor by methionine synthase (METH), but many algae such as the freshwater chlorophyte, Chlamydomonas reinhardtii, and the marine diatom, Phaeodactylum tricornutum, also have a B12-independent form of methionine synthase (METE). This means that they can utilize METH if B12 is available, but when it is absent or in limited supply, they use METE. To study the influence of vitamin exchange, CRISPR (clustered regularly interspaced short palindromic repeats) was used to make gene-edited metE mutants of both species. This enabled the study of the physiology of newly B12 dependent algae and mutualisms with B12-producing bacteria. As well as the role of B12 as a cofactor, it also acts to repress gene expression. Most notably, METE shows rapid and robust repression in the presence of B12 in both C. reinhardtii and P. tricornutum. This has been previously shown to occur through the promoter regions in both organisms. This dissertation has three main parts which are i) physiological and genetic consequences of acquired vitamin auxtrophy in C. reinhardtii and P. tricornutum; ii) bacterial mutualisms underpinned with B12 in C. reinhardtii and P. tricornutum; and iii) a comparative study of the regulation of C. reinhardtii and P. tricornutum METE using fluorescent reporters. To understand the physiological consequences of vitamin auxotrophy, the B12 requirement and response characteristics were determined for growth, growth rate, cell size chan…
abstract: Many organisms engage in symbiotic relationships that govern, to varying degrees, the function of ecosystems and their evolutionary history. It is important to understand the origins and dynamics of these systems. Especially important is the aquatic ecosystem, which is essential for approximately 50% of global primary production, and where many photosynthetic algae participate in symbiosis with bacteria where the latter provide vitamins such as cobalamin (vitamin B12) in exchange for fixed carbon from the algae. Vitamin B12 is used as a cofactor by methionine synthase (METH), but many algae such as the freshwater chlorophyte, Chlamydomonas reinhardtii, and the marine diatom, Phaeodactylum tricornutum, also have a B12-independent form of methionine synthase (METE). This means that they can utilize METH if B12 is available, but when it is absent or in limited supply, they use METE. To study the influence of vitamin exchange, CRISPR (clustered regularly interspaced short palindromic repeats) was used to make gene-edited metE mutants of both species. This enabled the study of the physiology of newly B12 dependent algae and mutualisms with B12-producing bacteria. As well as the role of B12 as a cofactor, it also acts to repress gene expression. Most notably, METE shows rapid and robust repression in the presence of B12 in both C. reinhardtii and P. tricornutum. This has been previously shown to occur through the promoter regions in both organisms. This dissertation has three main parts which are i) physiological and genetic consequences of acquired vitamin auxtrophy in C. reinhardtii and P. tricornutum; ii) bacterial mutualisms underpinned with B12 in C. reinhardtii and P. tricornutum; and iii) a comparative study of the regulation of C. reinhardtii and P. tricornutum METE using fluorescent reporters. To understand the physiological consequences of vitamin auxotrophy, the B12 requirement and response characteristics were determined for growth, growth rate, cell size chan…
author: Newsad, Shelby
language: eng
keywords: Mutualisms, B12 regulation, Chlamydomonas reinhardtii, Phaeodactylum tricornutum
license: https://www.rioxx.net/licenses/all-rights-reserved/
date published: 2022-07-31
date modified: 2026-07-22T22:24:04Z
provider: Cambridge University
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: University of Cambridge

PropertyValue
property ID: DOI
value: 10.17863/CAM.94427