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It turns out that we all need those zombie microbes that live indefinitely and don’t really evolve


Remember those sea floor organisms that may be individually 100 million years old? They weren’t all alone down there and the group as a whole offers challenging questions:

Last week in Science Advances, researchers presented the most complete picture to date of the strange, hidden biosphere beneath the seafloor. Ocean drilling expeditions have repeatedly probed those lightless depths and uncovered cells that survive almost in suspended animation, consuming orders of magnitude less energy than their neighbors at the surface. But the model presented in the new study shows that this zombielike state probably applies to the vast majority of microbes in ocean sediments — and that they typically subsist on energy budgets approaching a theoretical minimum for life.

Jordana Cepelewicz, “‘Zombie’ Microbes Redefine Life’s Energy Limits” at Quanta

Some researchers have worked out a theoretical minimum which, Cepelewicz tells us, “They found that for individual cells, this power minimum hovers around a zeptowatt, or 10-21 watts. That is roughly the power required to lift one-thousandth of a grain of salt one nanometer once a day. (For reference, a human body uses on average about 100 watts, the power of a reading light.)” The zombie cells are only a bit above that.

So stasis rules and, in the words of one researcher, “Our concept of how cells evolve goes out the window for this incredibly large biosphere.” And yet, we are told, “these almost-but-not-quite-dead cells play an important role in the production of methane, the degradation of the planet’s largest pool of organic carbon, and other processes.”

Paper. (open access)

See also: Claim: Microbes That Are – Individually – 100 Million Years Old Come Out Of Hibernation… Evolution? If they were in suspended animation for 100 million years, it’s not likely they were evolving at all. Jurassic Park under the microscope.

Polistra, a kilocalorie is energy to heat one kg of water 1 degree Celsius centred on 15 degrees C. This makes it into 4.184 kJ. For nutrition, calorie means kg calorie, i.e. kilocalorie. A 900 Cal slice of chocolate cake, has 3.766 MJ of available energy. Often that can be measured by burning. That's what, about 1/3 the suggested calorie intake for an active man with one shot, and it is then no wonder it takes a lot of exercise to burn it off. KF PS: at 100 W, we would burn up 8.64 MJ per day, a bit high, I used to see 50 - 100 W as heating load. The 50 W is more reasonable for that calorie intake figure. kairosfocus
The 100 watt reference is interesting and useful. Most discussions of human energy are given in calories, which is hard to compare with things like engines and light bulbs. I would have guessed the number was much larger. polistra

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