A broad study of the extremophile Chlamydomonas acidophila, isolated from an abandoned copper mine in Parys Mountain.

  • Owen Mcintosh

Student thesis: Phd


Anthropogenic activities have caused environmental damage for thousands of years, which has been exacerbated since the industrial revolution. Mining is one such activity that has caused damage to the environment, primarily through the creation of acid-mine drainage (AMD) waters. These are created when pyrite in rocks is exposed to oxygen and water, through mining, causing the formation of sulphuric acid. As the waters become more acidic, metals disassociate from the rocks leading to acidic and metal polluted waters. One such AMD system is Parys Mountain, Wales, where our lab has isolated an acidophilic microalga, Chlamydomonas acidophila – strain PM01. It exhibits higher tolerance levels of copper than other strains of the same species. Whilst tolerance ranges and physiological responses of eukaryotic extremophiles have been well studied, many of their mechanisms of adaptation have yet to be elucidated. PM01 provides a fantastic model to begin to understand some of these tolerance mechanisms. In order to tolerate the harsh conditions of AMD it is likely that C. acidophila has evolved differential responses to both pH differences and metal toxicity to non-adapted organisms, such as Chlamydomonas reinhardtii which is mesophilic in both its pH tolerance and its ability to survive metal toxicity. Firstly, in this thesis the physiological and biochemical responses of PM01 compared to the model organism Chlamydomonas reinhardtii (strain 11/32c) as well as other strains of C. acidophila (strains CCAP 11/136 and CCAP 11/137) were analysed in response to copper. Here it was found that PM01 is capable of growing at much higher copper concentrations than the other strains tested. Also, PM01 shuts down photosystem II after being exposed to copper for 3 hours, without the photosynthetic machinery appearing stressed. Additionally, a 2-stage non-photochemical quenching (NPQ) process was observed, where PM01 has different types of NPQ, depending on the actinic light intensity. The antioxidant capability of PM01 and C. reinhardtii was also measured. PM01 exhibited higher catalase activity, whilst the two isoforms of iron superoxide dismutase show different isoelectric points (pI). It was found that PM01 exhibits high levels of lipid oxidation in both short- and long-term copper stress, whereas C. reinhardtii only exhibited high lipid oxidation under a short-term copper stress. Finally, low lipid oxidation levels were shown in the other C. acidophila species, CCAP strains 11/136 and 11/137. Secondly, fast, high-throughput fingerprinting techniques were used to examine the metabolic and proteomic changes of PM01 and C. reinhardtii in response to copper stress. FT-IR spectroscopy revealed an increase in protein content upon copper exposure in PM01, but a decrease in lipids and carbohydrates. Whilst a similar response was seen in C. reinhardtii it was not to the same extent as PM01. MALDI-TOF mass spectroscopy provided a rapid overview of the proteome. Here protein peaks with a high m/z arising in the long-term copper-stress treated for both PM01 and C. reinhardtii. These protein peaks also suggested that a protein can “switch” between a single charge and double charge and could play an important role in either metal binding or reactive oxygen species quenching. An in-depth metabolomic analysis using LC-MS techniques reveal greater insights into PM01’s adaption to copper through the identification of several key metabolic changes between PM01 and C. reinhardtii. Thiol groups in metabolites such as cysteine and glutathione play a central role in copper adaptation. Additionally, amino acids such as proline, a known osmolyte, was found at elevated levels in PM01. Finally, I conducted a transcriptomic experiment was conducted to observe the global response of PM01 and C. reinhardtii to a long- and short-term copper stress. A whole host of transcripts were differentially expressed under copper stress, however, we managed to find 3 main processe
Date of Award1 Aug 2022
Original languageEnglish
Awarding Institution
  • The University of Manchester
SupervisorGiles Johnson (Supervisor), Jonathan Lloyd (Supervisor) & Jon Pittman (Supervisor)


  • metabolomics
  • LC-MS
  • transcriptomics
  • FT-IR
  • photosynthesis
  • algae
  • microalgae
  • copper
  • extremophile
  • acid mine drainage

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