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E. huxleyi, a unicellular marine alga, is a coccolithophore — it forms external calcium carbonate plates called coccoliths. Together, around 10–15 coccoliths form a coccosphere (Emiliania Huxleyi, n.d.). These intricate mineralized structures protect the cell and contribute significantly to the global carbon cycle. It also accumulates large amounts of lipids, up to 45-60% of the particulate organic carbon (POC), which serve as energy storage compounds (Fernández et al., 1996). E. huxleyi is quite a small organism; its diameter is around 4–5 μm (Emiliania Huxleyi, n.d.).
Figure I: E. Huxleyi under microscope (NCMA, n.d.)
E. huxleyi converts atmospheric CO2 into organic matter through photosynthesis, supporting marine food webs as a primary producer. It undergoes calcification, producing coccoliths made of calcium carbonate that eventually sink to the bottom of the ocean, sequestering CO2. This algae is known to form large blooms in the ocean that can extend thousands of kilometers (Emiliania Huxleyi, n.d.). These blooms can be visible from space because light reflects off the coccoliths (Summer Color in Northern Seas, n.d.). During growth, the algae synthesizes lipids such as triacylglycerols (TAGs) that accumulate in lipid droplets. This is promising for applications in sustainable energy (e.g., biofuel).
Figure II: E. Huxleyi bloom (Oceans at MIT, 2015)
This algae is special because it accumulates both calcium carbonate in the coccoliths and lipids (like TAGs, and alkenones) in lipid droplets. This allows the algae's metabolism and carbon fixation to be used for both bioconcrete and biofuel. It is widespread and abundant in oceans, and there has been extensive research on culturing E. huxleyi. These things make E. huxleyi special, so it is ideal for our project of converting CO2 into useful biomaterials.
Figure III: E. Huxleyi coccoliths under microscope (NCMA, n.d.)
What we want to answer about E. huxleyi is how its natural calcite accumulation and TAG production pathways can be engineered to enhance the yield of calcite and lipids, increasing production of biomaterials while helping mitigate global warming. We want test the effectiveness of introducing three different genes (NCE103, CA9, and DGA1) to E. huxleyi.
Figure IV: the TAG synthesis pathway in microalgal species (Sharma et.al., 2018)
Emiliania huxleyi. Bigelow NCMA. (n.d.). https://ncma.bigelow.org/CCMP371
Emiliania huxleyi. (n.d.). ScienceDirect. Retrieved October 3, 2025, from https://www.sciencedirect.com/topics/agricultural-and-biological-sciences/emiliania-huxleyi
Fernández, E., Fritz, J. J., & Balch, W. M. (1996). Chemical composition of the coccolithophorid Emilianid huxleyi under light-limited steady state growth. Journal of Experimental Marine Biology and Ecology, 207(1), 149–160. https://doi.org/10.1016/S0022-0981(96)02657-3
Sharma, P., Saharia, M., Srivastava, R., & Kumar, S. (2018, November). (PDF) tailoring microalgae for efficient biofuel production. Tailoring Microalgae for Efficient Biofuel Production. https://www.researchgate.net/publication/328092157_Tailoring_Microalgae_for_Efficient_Biofuel_Production
Summer Color in Northern Seas. (n.d.). NASA Earth Observatory. Retrieved October 3, 2025, from https://earthobservatory.nasa.gov/images/148705/summer-color-in-northern-seas
This satellite image shows a bloom of the marine algae E. Huxleyi turning the seawater off Newfoundland a milky turquoise. E. huxleyi and a related algal species, isochrysis, both produce long-chain hydrocarbons called alkenones. (courtesy of NASA Earth Observatory). Oceans at MIT. (2015, February 23). https://oceans.mit.edu/indexea5d.html?attachment_id=619126