Marine bacteria team up to break down one of the ocean's toughest carbon-storing molecules

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🗞️ Driving the news: A study published in Nature, led by Andreas Sichert of ETH Zurich and Otto X
• Cordero of MIT, shows that no single marine bacterium can fully degrade fucoidan, a complex carbohydrate produced by brown algae and diatoms
• Instead, bacterial strains divide the task, some breaking down the fucose-rich backbone while others remove side branches

🔭 The context: The team enriched a fucoidan-degrading community from coastal seawater and found over 453 genes producing fucoidan-acting enzymes across eight isolated strains, none capable of complete breakdown alone
• A simplified model trained on communities of one to three strains predicted degradation in communities of up to seven, and generalised across nine structurally different fucoidans from other algae

🌍 Why it matters for the planet: Fucoidan resists decay, so it can sink into the deep ocean carrying carbon and storing it for long periods, making it potentially significant in the ocean carbon cycle
• The researchers propose "diversity-limited degradation": where the right combination of complementary bacterial specialists is absent, fucoidan persists rather than breaking down
• That may explain why some algal carbon remains sequestered, and it ties long-term ocean carbon storage to microbial community composition rather than chemistry alone

⏭️ What's next: For biotechnology, the finding suggests assembling teams of complementary microbes rather than engineering a single organism to process brown algal biomass at scale
• The approach may also apply to other biopolymers whose chemistry has resisted description

💬 One quote: "The breakdown of one of the ocean's most abundant carbon pools rests on a division of labor, not between particular strains, but between functional roles" — Otto X. Cordero, associate professor of civil and environmental engineering, MIT

📈 One stat: More than 453 distinct fucoidan-acting enzyme genes across eight bacterial strains, none able to complete the breakdown alone.

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