Life on Earth may have appeared twice, new study suggests on origin of bacteria and archaea

Life on Earth might have a more complex origin story than previously understood, with a new study proposing that the transition from non-living chemistry to fully autonomous metabolism occurred not once, but twice.

The research, published in Science Advances, suggests that this crucial step happened separately for the two major branches of early life: bacteria and archaea. While the study maintains a common ancestor, known as LUCA (Last Universal Common Ancestor), it posits that LUCA had not yet developed a fully autonomous metabolism. Instead, the final stages of metabolic development are thought to have occurred independently after the evolutionary split of these two lineages.

One of biology's most challenging questions is explaining the emergence of the first cell. Earth is about 4.5 billion years old, and the oldest evidence of life dates back billions of years. However, there is a significant gap between the simple chemistry of the early planet and the first self-sustaining organisms. A living cell requires energy and a complex network of chemical reactions, its metabolism, to produce the molecules necessary for growth and reproduction.

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Viața pe Pământ ar putea avea o istorie mai complicată decât sugerează imaginea clasică a unui singur început.

The study tackles the puzzle of how these initial metabolic reactions functioned before cells possessed the sophisticated enzymatic systems seen today. The researchers estimate that the core metabolic network, essential for producing fundamental molecules like amino acids, nucleotides, and cofactors, involves approximately 400 chemical reactions. They hypothesize that early on, minerals and metals present in the geological environment may have catalyzed some of these reactions. Over time, these processes could have been gradually taken over and made more efficient by enzymes, essentially transitioning from geochemical processes to biological ones.

Alkaline hydrothermal vents on the ocean floor are highlighted as a potential natural laboratory for these early metabolic processes. These systems have long been considered a leading hypothesis for the origin of metabolism, offering a rich source of hydrogen, carbon dioxide, minerals, and metals conducive to chemical reactions. The models developed in this study explore how such environments could have facilitated the complex chemical pathways necessary for life's beginnings.

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O celulă vie are nevoie de energie și de o serie întreagă de reacții chimice pentru a produce moleculele necesare creșterii și reproducerii.