The Cells That Breathe Two Ways
Arthur T Knackerbracket has processed the following story:
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.
[...] 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 metabolisms simultaneously. It breathes oxygen and sulfur at the same time.
[...] RSW1 and any other microbes that have dual metabolism make intriguing models for how microbial life may have evolved during the Great Oxygenation Event, Boyd said. That must have been a quite chaotic time for microbes on the planet," he said. As a slow drip of oxygen filtered into the atmosphere and sea, any life-form that could handle an occasional brush with the new, poisonous gas - or even use it to its energetic benefit - may have been at an advantage. In that time of transition, two metabolisms may have been better than one.
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