“Dissolved carbon is relatively diluted compared to all other molecules in the ocean, which limits the growth of photosynthetic organisms that live there. We decided to study what happens when you alleviate this limiting factor by going in a carbon-rich location, where some organisms might have evolved the ability to use it to galvanize their growth,” said co-corresponding author Max Schubert, Ph.D., who was a scientist at the Wyss Institute of the Harvard University when the work was conducted and is now Principal Project Scientist at Align to Innovate. “This natural strain of cyanobacteria exhibits several characteristics that could be useful to humans, including very dense growth and a natural tendency to sink in water, making Chonkus a particularly interesting organism for future work on decarbonization and biomanufacturing. “

From the shallow sea to the laboratory bench

Schubert and fellow corresponding author Braden Tierney, Ph.D. first met as bench neighbors in the lab of Wyss faculty member George Church, Ph.D. nine years ago, but only began collaborating when both worked at Harvard Medical School (HMS) in 2016. Schubert, a microbiologist interested in building tools for the directed evolution of bacteria and their genomes, submitted a proposal to the HMS. 2019 Consortium for Space Genetics Climate Change Symposium to bring this work to cyanobacteria. He won the first prize, which funded his first forays into applying his tools to cyanobacteria to study their potential to fix and sequester carbon.

Meanwhile, Tierney, who was then a postdoctoral fellow co-supervised by Church, Schubert’s advisor, received a paper from a friend on shallow seeps – areas on the ocean floor where gases seep into water but are shallow enough to receive sunlight – and realized that there might be photosynthetic microbes living in these environments that had evolved to be able to capture dissolved CO₂ water. He established connections with Marco Milazzo, Ph.D. and Paola Quatrini, Ph.D., both professors at the University of Palermo in Sicily, who were actively studying the shallow seeps accessible nearby. Tierney secured funding for a collecting expedition from SeedLabs and contacted Schubert for help understanding and working with cyanobacteria that might be present in this environment.

Tierney and Schubert assembled a coalition that ultimately included scientists from the Wyss Institute, HMS, Weill Cornell Medical College, Colorado State University, University of Wisconsin-Madison, MIT, National Renewable Energy Laboratory in Colorado and several institutions in Palermo, Italy. The group launched a field expedition into the ocean off Vulcano where they donned diving suits and collected water samples from a CO.₂-rich shallow seepage. They then shipped tubes of seawater across the Atlantic to Boston, where scientists led by Schubert isolated and characterized the microbes living in the samples.

The bug of a microbe is a hallmark for humanity

To encourage their target cyanobacteria to grow, the researchers replicated the conditions in which a fast-growing cyanobacteria would thrive: warm temperatures, lots of light, and lots of CO.₂. After isolation from enrichment cultures, two fast-growing cyanobacteria strains were discovered: UTEX 3221 and UTEX 3222. The team chose to focus on UTEX 3222 due to its single-cell growth, making comparison easier. with existing strains of cyanobacteria.

UTEX 3222 produced larger colonies than other known fast-growing cyanobacteria strains, and its individual cells were also larger, hence the nickname Chonkus. It also achieved a higher density than existing strains, appeared to harbor carbon-containing storage granules in its cells, and had a higher overall carbon content than other strains: all potentially valuable traits for applications such as carbon sequestration and bioproduction. More interestingly, Chonkus quickly settled into a dense “green peanut butter”-like pellet at the bottom of its sample tubes, while other strains remained suspended. This behavior is particularly valuable for industrial processing, as the concentration and drying of biomass currently accounts for 15-30% of production costs.

“Many of the characteristics we observed in Chonkus are not inherently useful in their natural environment, but are very useful to humans. Aquatic organisms naturally grow at a very low density, but it is very useful to be able to grow up to high density at higher temperatures. useful in industrial environments that we use to make many goods and products, and can help sequester more carbon,” Tierney said. “There is an incredible amount of microbial diversity in the. world, and we think it’s more efficient to look for microbes that have already evolved to succeed in human-friendly environments rather than trying to create every trait we want in the lab. grew up E.coli bacteria. »

The team is excited about the many applications that could be addressed with Chonkus or modified versions of the microbe. Many organizations are studying the use of fast-growing organisms for carbon sequestration, and Chonkus may one day join their ranks. Several products are currently made from algae, such as omega-3 fatty acids, the antioxidant astaxanthin, and spirulina, and could be made more efficiently in a fast-growing, dense strain. And the fact that cyanobacteria directly harvest carbon from their environment to grow means they can couple the processes of carbon sequestration and biomanufacturing in a single organism. Samples of UTEX 3222 and UTEX 3221 are cryopreserved and publicly available for other researchers to use at the Culture Collection of Algae at the University of Texas at Austin.

Inspired by the success of their first expedition, Tierney has since co-founded a nonprofit organization with paper co-authors Krista Ryon and James Henriksen, called The Two Frontiers Project, which aims to study how life develops in extreme environments thanks to the next generation. scientific expeditions. The group has already made subsequent expeditions to hot springs in Colorado, to the steaming lands of the Tyrrhenian Sea, to the coral reefs of the Red Sea, and more. The organization focuses on microbes that have uses for three major applications: carbon capture, CO₂ recycling for sustainable products and restoration of the coral ecosystem.

“The inherent characteristics of the naturally evolved cyanobacteria strains described in this research have the potential to be used in both industry and the environment, including the biomanufacturing of useful carbon-based products or the immersion of large volumes of carbon in the seafloor Although further modifications could be made to improve the capabilities of these microbes, harnessing billions of years of evolution is a significant advance in humanity’s urgent need to mitigate. and reverse climate change,” said Church, who is also the Robert Winthrop Professor of Genetics at HMS and professor of Health Sciences and Technology at Harvard and MIT. safety before building the car” – our lab is also studying biocontainment approaches that help contain and control these types of experiments.”

“The Wyss Institute was founded on the belief that nature is the best source of innovation on the planet and that emulating its principles is the key to generating positive impact. I am proud of this team who went out of the laboratory and pursued ideas from nature. best ideas where they have already been developed. This is a wonderful example of how our new Sustainable Future Initiative is pursuing original approaches to tackling climate change – the greatest challenge of our generation,” said Don, founding director of Wyss. Ingber, MD, Ph.D., who is also the Judah Folkman Professor of Vascular Biology at HMS and Boston Children’s Hospital and at Hansjörg Wyss Professor of Biologically Inspired Engineering at Harvard’s John A. Paulson School of Engineering and Applied Sciences.

Other authors of the article include Tzu-Chieh Tang, Isabella Goodchild-Michelman, Krista Ryon, James Henriksen, Theodore Chavkin, Yanqi Wu, Teemu Miettinen, Stefanie Van Wychen, Lukas Dahlin, Davide Spatafora, Gabriele Turco, Michael Guarnieri, Scott Manalis, John Kowitz, Raja Dhir, Paola Quatrini, Christopher Mason and Marco Milazzo.

This research was supported by the U.S. Department of Energy (DOE) under grant no. DE-FG02-02ER63445 and by price no. MCB-2037995, SEED Labs, WorldQuant Foundation, Weill Cornell Medical College Scientific Computing Unit (SCU), and International CO₂ Natural Analogue Network (ICONA).