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The Sciences

Bacteria Survive & Reproduce in Gravity 400,000X Stronger Than Earth's

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E. coli

What's the News: Some bacteria can live in extreme "hypergravity," found a new study

published in the Proceedings of the National Academy of Sciences, surviving and reproducing in forces 400,000 times greater than what's felt on Earth. These findings fit with the idea that microbes carried on meteorites or other debris---a ride that would have subjected them to hypergravity-strength forces---may be the ancestors of life on Earth. How the Heck:

  • While measuring the density of the common intestinal bacteria Escherichia coli, the researchers noticed that the bacteria seemed undeterred by spinning around at the equivalent of 7,500 G's---so they decided to see how much pressure these microbes could handle.

  • The researchers spun samples of E. coli and three other types of bacteria in an ultracentrifuge, to generate hypergravity conditions.

  • E. coli and one other bacteria, Paracoccus denitrificans, could not only survive but continue to reproduce at 403,627 G's, the scientists found, though its proliferation was stunted compared to what it is at Earth-level gravity. The other two species couldn't endure such extreme gravitational forces, but all four could reproduce at least somewhat at 20,000 G's.

What's the Context:

  • Extremophile microbes have been observed going about their business under all kinds of seemingly inhospitable conditions, from sub-glacial lakes in Antarctica to anaerobic crevices deep in the Earth's crust. These species, scientists think, suggest how life may survive the extreme temperatures or lack of oxygen elsewhere in the universe.

  • Finding that bacteria do so well in hypergravity, the researchers wrote, likewise suggests that "the habitability of extraterrestrial environments must not be limited by gravity."

  • Long-ago asteroids and comets that may have carried alien microbes to Earth were likely accelerated to around 300,000 G's, which this study suggests microbes could have survived. These findings also open up more places to search for life today, such as brown dwarf stars, with surface gravity of 10 to 100 G's and, in some cases, temperatures that may be cool enough to support life.

  • Humans can't come close to surviving, let alone making more humans, under these conditions; we tend to lose consciousness at about five times Earth's gravity.

Reference: Shigeru Deguchi, Hirokazu Shimoshige, Mikiko Tsudome, Sada-atsu Mukai, Robert W. Corkery, Susumu Ito, and Koki Horikoshi. "Microbial growth at hyperaccelerations up to 403,627 × g." Proceedings of the National Academy of Sciences online, April 25, 2011. DOI:10.1073/pnas.1018027108

Image: Lawrence Berkeley National Laboratory

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