LUCA, the Last Universal Common Ancestor

LUCA hydrothermal vent

LUCA might have lived in the hydrothermal vents existing on Earth 4 billion years ago.

The scientists from Heinrich Heine University in Dusseldorf, Germany found what they called the Last Universal Common Ancestor.

Up until now, there had been no evidence to support the identity of our common ancestor.

The research team took into consideration almost 6.1 million genes coming from unicellular species. After creating a family tree for each gene, they used computer analysis to find connections between the domains.

The two forms of unicellular organisms are bacteria and archaea. The first doesn’t have a nucleus, and the second has a different cellular structure.

The results of the research showed that LUCA might have been an anaerobic organism that was capable of obtaining nutrients from its surroundings. The organism should have been capable of ATP synthesis and carbon and nitrogen metabolism.

LUCA is also supposed to have contained enzymes such as nitrogenases and hydrogenases, which made it able to live off carbon dioxide, nitrogen gas or hydrogen gas. These chemical substances are often found in the underwater hot vets and hydrothermal environments.

„The concept of a last universal common ancestor of all cells (LUCA, or the progenote) is central to the study of early evolution and life’s origin, yet information about how and where LUCA lived is lacking,” said the authors in the abstract of the study.

The research ended up with 355 family trees, which helped the scientists map the evolution of life on Earth.

The nitrogen gas dependent bacteria were the closest to LUCA, as being one of the most common organisms on our planet. These include Clostridia, which produces tetanus, colitis and gangrene, and the Methanogens class. They can survive through the assimilation of methyl compounds.

Nitrogen gas occurs naturally from serpentinization, a process where the iron from the Earth’s mantle oxidizes and creates the gas.

LUCA is estimated to have appeared 4 billion years ago when our planet underwent the last phase of heavy bombardment from asteroids coming from Mars, Venus, or Mercury. The scientists presumed that the heat from the explosions caused the oceans to boil, leaving the atmosphere without oxygen, and therefore creating an ideal environment for a bacterium such as LUCA.

The first efforts to find LUCA took place in 1977, when researchers pointed out that life could have evolved in conditions that until then seemed inhospitable, such as hydrothermal vents, submarine caves or Antarctic ice.

Even if LUCA is the oldest known ancestor, the scientists believe it is possible that the bacteria were not the first living thing that appeared on Earth. It may be that there had been previous attempts at creating life, most of which failed because of the environment.

The origin of life is a question that had long intrigued the scientists, and maybe the present discovery may shed some light on how Earth managed to become the host of a miracle.

Image Source: Wikipedia

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