A recent study published in PNAS offers new insights into how the very first life forms on Earth utilized hydrogen gas (H2) as an energy source. The research, led by a team from the University of Düsseldorf and the Max Planck Institute for Terrestrial Microbiology, provides a simpler explanation for this crucial step in the origin of life.
Hydrogen gas, a clean fuel that burns without producing CO2, has long been recognized as a potential solution for sustainable energy needs. The new study reveals that microbes have been utilizing H2 for as long as life has existed on Earth. These early life forms thrived in deep-sea hydrothermal vents and hot rock formations, environments believed to be the cradle of life itself.
For cells to harvest energy from H2, they need to push electrons uphill, which is an energetically unfavorable process. Scientists previously discovered that cells achieve this through a complex mechanism called electron bifurcation, involving multiple enzymes.
The new study proposes a simpler explanation for how early life forms might have harnessed H2 before the evolution of enzymes. The research suggests that under the naturally alkaline conditions of hydrothermal vents, iron surfaces could directly split the H2 molecule. This process generates electrons that can be transferred to ferredoxin, an ancient biological electron carrier, without the need for complex proteins.
The study highlights the role of metals, particularly iron, in facilitating this process. Iron-rich environments like hydrothermal vents could have provided the necessary conditions for H2 utilization by early life forms. This finding aligns with the theory that life originated in these environments.
The ability to utilize H2 for energy production is a fundamental aspect of life on Earth. This research provides a simpler explanation for how this process might have occurred at the origin of life, suggesting that basic chemical reactions under the conditions found in hydrothermal vents could have played a crucial role.
While the study focuses on iron, the researchers are exploring the potential role of other metals in facilitating early life's use of H2. Further research will delve deeper into understanding the complex interplay between early life forms, their environment, and the utilization of H2 as an energy source.
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