Our focus is on understanding the biological processes that underlie key ecological and biogeochemical processes in the oceans, ranging from cellular signalling, membrane transport, host- virus interactions, harmful algae and the roles of marine microbes in oxidation-reduction reactions, particularly in the sea surface layer. The programme has both fundamental and strategic relevance and we work with a wide range of international collaborators with a general aim to integrate understanding at molecular, cellular, population community and ecosystem levels.
Coccolithophores are marine algae that play a major role in the global carbon cycle through their production of calcium carbonate scales (coccoliths). Coccolithophores are the most abundant calcifying organisms in the oceans and are one of the most remarkable groups, as calcification unlike in most other calcifying organisms, occurs inside the cell rather than at the cell surface. Coccolithophores have therefore developed highly specialized physiological processes to support a sustained uptake and transport of the substrates (calcium and bicarbonate ions) and products (calcium carbonate and protons) of the calcification reaction. Ocean acidification is predicted to have a signifi cant impact on calcifying organisms, as the formation and dissolution of calcium carbonate is highly sensitive to pH. We aim to understand more about the underlying mechanisms and to identify how calcifi cation may be impacted by future changes in ocean chemistry. Funding from the NERC Oceans 2025 strategic programme in marine science, the UK Ocean Acidification Research Programme, the EU Framework 7 EPOCA (European Project on Ocean Acidification) and the Marie Curie Training Network CalMarO (Calcifi cation in Marine Organisms) is allowing detailed collaborative studies of the ion transporters required for the uptake of calcium and bicarbonate in coccolithophores and the roles of other proteins that are involved in the regulation of coccolith formation. Professor Colin Brownlee and co-workers have identified a number of transport proteins that appear to be closely involved in the calcification process. This work is producing unexpected findings, including the discovery of a membrane proton-conducting channel that was previously only known in certain types of animal cells.
Signalling in algae
Cilia and flagella are responsible for many essential processesin cell biology, from the propulsion of individual sperm cells to the coordinated beating of cilia in our respiratory tracts. In addition to their well characterized roles in motility, recent evidence suggests that they play important roles as cellular sensors and even in regulating the cell cycle. The motile green alga, Chlamydomonas, has long been used as a model system to understand flagella structure and function and research in this organism has enabled the identification of ciliary defects as the underlying cause of several human genetic disorders. A BBSRC-funded project led by Professor Brownlee and Dr Glen Wheeler (Plymouth Marine Laboratory) is allowing the application of high resolution fluorescence techniques to image signalling processes in Chlamydomonas flagella in order to understand more about the cellular role of these organelles. Combining advanced microscopy with molecular genetics is allowing the functions of particular flagellar membrane ion channels in signaling and motility to be studies in depth.
Our work on signaling also focuses on the evolution of calcium signalling. We study the phyolgenetic distribution of calcium channels in a range of eukaryotes, including plants, green red and brown algae to give clues about how calcium channels evolved. This work is giving some surprising insights into the nature and origin of membrane electrical excitability.
Dr. Declan Schroeder’s team studies how cells of the coccolithophore Emiliania huxleyi are infected by viruses and the roles of viruses in regulating the biology and ecology of coccolithophores. They study how the virus EhV-86 enters its coccolithophore host cells and carry out research aimed at developing a mechanistic understanding of virus infection strategy. This group also studies the genetic diversity of virus populations in relation to changes in host population structure by applying molecular analysis to the preserved phytoplankton archive of the Continuous Plankton Recorder.
Populations of the small filamentous brown alga Ectocarpus siliculosus across the world are commonly infected by a large DNA virus (NCLDV), EsV-1, which integrates its genome into that of the host. Often, these infections are silent, since although the virus is present and can be detected by molecular genetic approaches, symptoms are rarely visible. In collaboration with co-workers at the Station Biologique, Roscoff Dr Schroeder’s group is using molecular techniques to assess the host range of these viruses, in a bid to elucidate their potential impacts on brown algal populations and how these may be affected by environmental change.
Marine microbes: uncovering novel biogeochemical processes
Carbon monoxide (CO) is produced in the oceans and is transferred into the atmosphere, where it is a potent secondary greenhouse gas. Fortunately most of the CO produced is oxidized by microorganisms and is unable to escape into the atmosphere. Genome analyses have shown that many carbon monoxide dehydrogenase (cox) genes are present in certain types of marine bacteria, particularly those of the Marine Roseobacter Clade (MRC), suggesting a role for the MRC in CO biogeochemical cycling. Dr Michael Cunliffe is studying the cox genes of these bacteria to better understand to potential for different bacterial types for oxidizing CO.