The Cells That Breathe Two Ways -- Quanta Magazine

[erronis]

https://www.quantamagazine.org/the-cells-that-breathe-two-ways-20250723/

In a hot spring at Yellowstone National Park, a microbe does something that life shouldn’t be able to do: It breathes oxygen and sulfur at the same time.

Grand Prismatic Spring at Yellowstone National Park has the kind of chaotic chemistry — with both oxygen-rich and oxygen-free areas — that may support dual respiration.

Take a deep breath. A flow of air has rushed into your lungs, where the oxygen moves into your bloodstream, fueling metabolic fires in cells throughout your body. You, being an aerobic organism, use oxygen as the cellular spark that frees molecular energy from the food you eat. But not all organisms on the planet live or breathe this way. Instead of using oxygen to harvest energy, many single-celled life-forms that live in environments far from oxygen’s reach, such as deep-sea hydrothermal vents or stygian crevices in the soil, wield other elements to respire and unlock energy.

This physical separation of the oxygen-rich and oxygen-free worlds is not merely a matter of life utilizing available resources; it’s a biochemical necessity. Oxygen doesn’t play nice with the metabolic pathways that make it possible to respire with the use of other elements, such as sulfur or manganese. It gives aerobes like us life, but for many anaerobes, or creatures that respire without oxygen, oxygen is a toxin that reacts with and damages their specialized molecular machinery.

. . .

For the first couple billion years of life on Earth, organisms avoided this predicament altogether. Back then, the air and oceans were mostly devoid of oxygen, so life was almost entirely anaerobic, or non-oxygen-breathing. Then, around 2.7 billion years ago, the seas filled with industrious, photosynthetic cyanobacteria. They had invented a way to turn sunlight into sugar and oxygen, and they flourished. Over hundreds of millions of years, their accumulated breathing filled the atmosphere and oceans with oxygen. This so-called Great Oxidation Event was a pivotal transformation (opens a new tab) in the biosphere and the physical chemistry of Earth’s atmosphere and oceans. In this new environment, aerobic respiration evolved to dominate the world.

An ongoing mystery for researchers is how life navigated the shift from anaerobic to aerobic respiration; so much microbial biodiversity had to adapt to a world filled with what was once a biochemical bane. Now researchers have fresh insight into what that transition could have looked like billions of years ago, gleaned from an organism living today. A bacterium that researchers collected from the cauldron of a Yellowstone National Park hot spring does something that life really shouldn’t be able to do: It runs aerobic and anaerobic metabolism (opens a new tab)s simultaneously. It breathes oxygen and sulfur at the same time.

. . .