A deadly gas to humans may actually be what kickstarted life on Earth

MELBOURNE, Australia — Life on Earth appears to owe its existence to a gas that’s deadly to present-day humans, a new study reveals. Scientists in Australia say carbon monoxide appears to be responsible for creating the first organisms, explaining how microbes in the deep ocean survive without sunlight.

On land, however, the gas sends tens of thousands of people to the emergency room every year in the United States. The discovery reverses the idea that marine ecosystems rely on the Sun. According to the new study, many get their energy from carbon monoxide and hydrogen — an alternative to photosynthesis, which the researchers call “chemosynthesis.”

The five-year study found the gases fuel trillions of microbes in the sea, ranging from the tropics to the poles. They are dominant in areas so dark and nutrient-poor that even starlight cannot reach them.

“What about those regions so deep that light can’t penetrate or so nutrient-poor that algae can’t thrive? We showed in this study that instead chemosynthesis is dominant in these regions,” says lead author Professor Chris Greening of Monash University in a media release.

“Hydrogen and carbon monoxide in fact ‘fed’ microbes in all regions we’ve looked at: from urban bays to around tropical islands to hundreds of meters below the surface. Some can even be found beneath Antarctica’s ice shelves.”

How did the team find life that doesn’t need sunlight?

The Australian team combined molecular measurements during voyages with experiments on organisms grown in the lab. They also used a technique called metagenomic sequencing, identifying genetic blueprints of the tiny bugs.

“We found the genes that enable hydrogen consumption across eight distantly related types of microbes, known as phyla, and this survival strategy becomes more common the deeper they live,” adds co-lead author Dr. Rachael Lappan.

The researchers were inspired by bacteria found in soil. They have previously shown most exist by consuming hydrogen and carbon monoxide from the atmosphere.

“The surface layers of the world’s oceans generally contain high levels of dissolved hydrogen and carbon monoxide gases due to various geological and biological processes. So it made sense that oceanic bacteria used the same gases as their terrestrial cousins,” Dr. Lappan continues.

The findings in the journal Nature Microbiology improve our understanding of how life evolved.

“The first life probably emerged in deep-sea vents using hydrogen, not sunlight, as the energy source. It’s incredible that, 3.7 billion years later, so many microbes in the oceans are still using this high-energy gas and we’ve completely overlooked this until now,” Prof. Greening concludes.

Could the findings point to life on other planets?

Studies suggest that exoplanets outside the solar system could be even more habitable than Earth. Billions of years ago, the early universe contained only hydrogen and helium.

The gases could extend the period life has to evolve. These gases are also readily available in the planet-forming materials around young stars, such as our Sun. All planets built up atmospheres that were dominated by them. Earth eventually favored heavier elements.

South West News Service writer Mark Waghorn contributed to this report.

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