Tiny diatoms found in the ocean are highly effective at absorbing carbon dioxide (CO2) from their surroundings. They can utilize as much as 20 percent of the Earth’s CO2. A research group from the University of Basel in Switzerland has recently identified a protein shell within these algae that is essential for proficient CO2 fixation. This significant finding could lead to innovative bioengineering strategies aimed at mitigating atmospheric CO2.
Diatoms, although microscopic and invisible to the naked eye, are among the most prolific algae species in the ocean, playing a crucial part in the global carbon cycle. They use photosynthesis to take in substantial amounts of CO2 from the environment and transform it into nutrients that support much of marine life. However, the exact mechanisms that allow diatoms to be so effective in this process have remained largely unexplored.
A team of researchers led by Prof. Ben Engel at the University of Basel’s Biozentrum, collaborating with scientists from the University of York in the UK and Kwansei-Gakuin University in Japan, has uncovered a protein shell integral to the CO2 fixation process in diatoms. With advanced imaging technologies like cryo-electron tomography (cryo-ET), the researchers unveiled the molecular structure of this protein sheath, dubbed PyShell, and clarified its function. The findings have been published in two articles in Cell.
Importance of PyShell in CO2 fixation
Photosynthesis occurs in chloroplasts in plants and algae. Within these chloroplasts, thylakoid membranes harness energy from sunlight, subsequently assisting the enzyme Rubisco in fixing CO2.
However, algae have a distinct advantage: they concentrate all their Rubisco into small structures known as pyrenoids, which allows for more efficient CO2 capture. “We have found that diatom pyrenoids are surrounded by a lattice-like protein shell,” states Dr. Manon Demulder, a contributor to both studies. “The PyShell not only maintains the structure of the pyrenoid but also enhances CO2 concentration within this compartment. This enables Rubisco to effectively fix CO2 from the ocean and convert it into nutrients.”
When the researchers disabled the PyShell in the algae, their capacity to fix CO2 was greatly diminished. There was a noticeable decline in photosynthesis and cell growth. “This demonstrated how critical the PyShell is for effective carbon capture—a process fundamental to oceanic ecosystems and the global climate,” remarks Manon Demulder.
Advances in CO2 reduction through bioengineering?
The revelation of the PyShell could pave the way for promising biotechnological initiatives aimed at addressing climate change, one of the most urgent issues we face today. “Firstly, we must reduce our CO2 emissions to slow climate change. Immediate action is necessary,” emphasizes Ben Engel.
“The CO2 we emit today will linger in the atmosphere for millennia. We hope discoveries like the PyShell can motivate new biotechnological applications that heighten photosynthesis and enhance atmospheric CO2 capture. While these are long-term aspirations, it is crucial to engage in foundational research now to unlock future carbon-capture advancements.”
