What is Luca, the last universal common ancestor

Luca is the representation of a crucial node in the tree of life. This organism, which is identified as a bacterium belonging to the planktycetes edge, is the predecessor of the three domains we know: Archaea, Bacteria and Eukaryota. Recent research led by Damien Devos and his team has challenged the traditional vision of the evolution of life, suggesting that Luca possessed unique characteristics that are not limited to bacteria, which implies a greater complexity in their structures and functions.

Traditionally, it was thought that the tree of life was divided into three branches: eukaryotes, bacteria and arches, with Luca at the base. The differences between bacteria and arches are found in chemical and metabolic aspects, while eukaryotes represented a significant evolutionary innovation by developing cells with nuclei and organelles.

Luca’s study also has important astrobiological implications. The environments that could have housed Luca, such as hydrothermal vents, are common in places like Europe and Encela, Jupiter and Saturn moons, respectively. The existence of subsurface oceans in these moons suggests that they could provide the necessary conditions for life. This leads to the conclusion that Chemical energynot sunlight, It was fundamental for the origin of life. Luca, according to recent research, could prosper in dark and mineral environments, which opens new possibilities for the search for life in extraterrestrial environments.

We recommend reading this article about the eukaryotic cell: what is, characteristics, parts and functions.

It is approximated that Luca existed approximately 4.2 billion years agowhich represents a relatively short period after the formation of the land and our solar system. This conclusion derives from an investigation by Edmund Moody and his team at the University of Bristol, who compared the genes of various living species to track the mutations that occurred since they shared an ancestor in Luca.

Luca’s search began with the Charles Darwin ideaswho proposed that all modern life descended from a primary organism. As science advanced, especially after the decipherment of the genetic code in the twentieth century, the theory gained support. It was discovered that the genetic code is universal for all organisms on Earth, which suggests a common ancestor.

Luca studies indicate that This unicellular organism could have used RNA both to store genetic information and to catalyze chemical reactions, similar to how some modern enzymes do. In addition, it is believed that Luca was resistant to extreme conditions, possibly living near hydrothermal sources at the bottom of the ocean.

The recent analysis has also revealed that, over millions of years, Luca’s genes have redistributed between different species through a process known as Horizontal gene transfer (LGT). The researchers managed to identify 355 genes that seem to have been inherited directly from Luca and have not suffered LGT, which provides clues about their way of life.

• Structure and composition: These characteristics include a developed endomembrane system, condensed DNA and the presence of sterols in some of its membranes, aspects that bring eukaryotes more than to typical bacteria.
• Early immune system: Investigations indicate that Luca had a primitive immune system, which implies that it was already in an “arms race” with viruses, even 4.2 billion years ago.
• Interconnected ecosystem: Luca probably didn’t live in isolation. Their waste served as nutrients for other microorganisms, creating a recycling ecosystem in which different species coexisted and benefited each other.
• Anaerobic and autotrophic metabolism: This organism did not breathe oxygen, but manufactured its own food from environmental compounds, such as hydrogen, carbon dioxide and nitrogen. His metabolism allowed him to convert these elements into useful compounds, such as ammonia.
• Carbon fixing: Luca used the Acetyl-Coa road, one of the oldest and simplest routes to fix the CO₂, which allowed him to assimilate carbon efficiently in a metal rich environment.
• Extensive genome: It is estimated that Luca had a genome of at least 2.5 megabaases, encoding around 2,600 proteins. This is comparable to the genomes of many modern prokaryotes, which suggests a high level of genetic diversity.
• Adaptation to extreme environments: The presence of a gene for an enzyme called “reverse girase”, which is found in modern extremophiles, supports the idea that Luca prospered in high temperature conditions.
• Genetic redundancy: Luca possessed significant genetic redundancy, suggesting that the loss of some genes did not drastically affect their functioning. This could explain some anomalies in the phylogenetics of current organisms.
• Molecular hydrogen production: Luca probably used molecular hydrogen as a source of energy, a byproduct of chemical reactions that occurred in its surroundings. This process was fundamental for its metabolism and supported its biological activity.

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