Adaptation mechanisms of globally successful cyanobacteria

Dr Ivo Tews, Dr Phyllis Lam, Prof Eric Achterberg, Dr Martha Gledhill, Dr Thomas Browning

Cyanobacteria are the most abundant photosynthetic organisms on the planet. To adapt to the highly varied physical and chemical marine environment, cyanobacteria use diverse strategies that allows them to thrive in many aquatic habitats, including the vast nutrient-depleted gyres of the low latitude oceans.

Your project will take a molecular approach to understanding this ecological success story. You will characterise and compare molecular systems that are suited to study adaptation strategies. To understand adaptation is a highly interdisciplinary scientific challenge; this project will include fieldwork study, developing an understanding of the biogeochemistry of the oceans, and include the study of the biochemistry of specific molecular machines. A primary target of this PhD is iron homeostasis: iron uptake systems and selected key enzymes that are upregulated under iron limitation are to be studied, starting with housekeeping enzymes such as metal dependent fructose 1,6-bisphosphate aldolase.

The reward of a molecular approach is not only a better understanding of adaptation strategies but also the application of this knowledge for developing future technologies or efficient processes. This might include novel and highly efficient proteins, both in function and structure, and optimised enzymes that can be used as a molecular tool-kit.


Biochemical and structural characterization of protein targets allows us to understand adaptation on a molecular level. Iron homeostasis is a key interest of our work (1, 2). To understand the ability of cyanobacteria to tailor their physiology requires comparison between natural samples found in the ocean (3), their cultured counterparts, and heterologous cyanobacteria. An example that serves as a start point in the PhD is the enzyme fructose 1,6-bisphosphate aldolase from the marine diazotroph Trichodesmium – a physiological switch between metal-containing / metal-free enzymes occurs, depending on nutrient conditions they are growing under. The preliminary data on recombinant protein purification and crystallization, with crystals already obtained (unpublished), serve to kick-start this project.

The experimental workflow will include: (i) the study of molecular properties through biochemical and structural characterization: recombinant protein expression, protein purification, crystallization and protein structure determination (1); (ii) collection and analysis of samples for microbial metallomes on a cruise of opportunity (German GEOTRACES); metallomes will be analyzed using the high-resolution mass spectrometry facility at GEOMAR to provide cellular metal composition on a bulk particulate basi; (iii) samples will be collected from shipboard bioassay experiments that will alter individual nutrients (e.g. iron) available to microbial communities to further support interpretation of the measured metallomes and their variability between samples collected in different environmental settings.

University of Southampton

The INSPIRE DTP programme provides comprehensive personal and professional development training alongside extensive opportunities for students to expand their multi-disciplinary outlook through interactions with a wide network of academic, research and industrial/policy partners. The student will be registered at the University of Southampton and hosted at the Institute for Life Sciences. Specific training will focus on marine biogeochemistry, including participation on a cruise of opportunity with the partner GEOMAR, biochemical work including protein purification and characterisation, and lastly structural biology embedded in the training framework of the host group; you will participate at national workshops in the technique. The combination of expertise in this PhD is truly multidisciplinary, and the associated training will result in a highly marketable skill set.


Eligibility & Funding Details: 

Please check for details.  


Background Reading: 
  1. Polyviou D, Machelett MM, Hitchcock A, Baylay AJ, MacMillan F, Moore CM, Bibby TS, Tews I. Structural and functional characterisation of IdiA/FutA (Tery_3377), an iron binding protein from the ocean diazotroph Trichodesmium erythraeum. J Biol Chem. 293 (2018), 18099-18109.
  2. Browning TJ, Achterberg EP, Rapp I, Engel A, Bertrand EM, Moore CM. Nutrient co-limitation at the boundary of an oceanic gyre. Nature 551 (2017), 242–246.
  3. Reintjes G, Tegetmeyer HE, Bürgisser M, Orlić S, Tews I, Zubkov M, Voß D, Zielinski O, Quast C, Glöckner FO, Amann R, Ferdelman TG, Fuchs BM. On-Site Analysis of Bacterial Communities of the Ultraoligotrophic South Pacific Gyre. Appl Environ Microbiol. 85 (2019), e00184-19.