Ancient microbes that thrive in some of the world's most extreme environments have unveiled how humans adjusted to a changing atmosphere over billions of years, according to a study.
The findings, published in the journal Cell, have detailed the structure of MBH, a molecular complex involved in microbial respiration.
The near-atomic resolution images are the first ever of MBH and show that its structure is remarkably similar to its counterpart in humans, Complex I.
"Nature is really good at finding molecules that work and then modifying them and using them over and over again. This is a prime example," said Michael W W Adams, a professor at University of Georgia (UGA) in the US.
"Knowing the structure of MBH provides us with new insights into how Complex I evolved and how it might work," said Adams.
Almost all life on Earth relies on respiration, which converts electrical energy into a usable, chemical form.
MBH and Complex I are important parts of this process; however, until now, the evolutionary connection between them was unclear.
MBH's structure also illustrates a mechanism for transducing electrical energy into chemical energy that is simpler than that in Complex I.
"The determination of MBH's structure fills in some important missing pieces that reveal how life adjusted to sweeping changes in the environment throughout the millennia," said Huilin Li, a professor at Van Andel Research Institute (VARI) in the US.
"This solves a fundamental, longstanding mystery in biology," said Li.
MBH is regarded as an ancient respiratory system because it was isolated from Pyrococcus furiosus, a microbe that grows best in boiling water and that for billions of years has made its home in volcanic marine vents.
This inhospitable environment, with its noxious mix of gases and extreme temperatures, is akin to the atmospheric conditions present on a much younger, much more volatile planet, researchers said.
Although many aspects of the two complexes are similar, Complex I boasts several extra loops that allow it to interact with more molecules than MBH, an adaptation that likely arose along with a shift in the Earth's atmospheric makeup, they said.
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