Season 17, Episode 37: Can Cyanobacteria Save the Climate? Chuck’s Fantastic Idea Explained

Hey StarTalkians! Season 17, episode 37 showcased one of the rare occasions where Chuck’s off-the-cuff questions make Neil sit back and think. In the midst of a discussion about oxygen’s role in the atmosphere, Chuck dropped this fantastic suggestion:

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(17:50)

The idea is simple: since cyanobacteria get energy from photosynthesis, taking in CO2 and releasing oxygen, couldn’t they help us mitigate climate change? I looked into the idea, and broadly, yes, Chuck is kind of right.

Cyanobacteria and RuBisCO

The science behind Chuck’s suggestion revolves around the Calvin-Benson-Bassham cycle, the most important mechanism for biological “carbon fixing.” The enzyme at the centre of this is called ribulose‐1,5‐bisphosphate carboxylase/oxygenase, or (thankfully) RuBisCO for short. This one enzyme is responsible for about 95% of carbon fixed by the biosphere, and about 30% of primary fixation comes from cyanobacteria specifically.

The Problems with RuBisCO

RuBisCO does a lot of work, globally, but it lacks in the efficiency likely needed to combat humanity’s impact on the climate. It’s quite slow generally, and it turns out that RuBisCO mistakenly acts on oxygen instead of CO2 about 20% of the time. Back when it evolved, this wasn’t a huge issue, because atmospheric oxygen was rare – it was the period Neil was talking about. But in today’s oxygen-rich environment, it’s a bigger problem.

However, attempts to improve its specificity generally slow it down. It’s like a busy employee, if there’s a tight deadline, mistakes are more common. But if you need it to be accurate, it will take longer.

Fixing the Carbon Fixer

Scientists are working on ways to improve this process, with methods ranging from enzyme engineering to AI-powered optimizations. One interesting study involved genetically engineering cyanobacteria to boost CO2 fixation. They altered the genome to boost production of a crucial chemical for carbon fixation, and deleted a gene that slows down the process. While there is still a lot of work to do, approaches like this appear to be effective.

Could it Really Work?

Although it’s not ready to implement yet, it’s estimated that approaches like this could sequester between 3.6 and 6.3 gigatons of carbon per year . For reference, human emissions are about 38 gigatons per year – about six times higher. It’s not a silver bullet, but Chuck really was onto something.