Where did the first cell come from?
How and where did the first cells live?
How and where did the first cells live on early earth? And what did they feed on? According to a new Düsseldorf study, the common ancestor of all life (last universal common ancestor, LUCA for short) lived around 3.8 billion years ago at a hot deep-sea hydrothermal spring. It didn't need oxygen and lived on hydrogen and carbon dioxide: gases that are always abundant at deep-sea springs. He could fix nitrogen, his metabolism needed metals as catalysts. LUCA represents the link between the chemical origin of life and the first free-living cells, and the deciphering of its properties is an important step in the study of early evolution.
How and where did LUCA live?
Prof. Dr. William Martin and his colleagues from the Institute for Molecular Evolution at HHU started with the genes of modern organisms and read from them how and where LUCA lived. It was known from previous studies that LUCA could store and read genetic information. However, so far no information was available on how and where LUCA lived. The researchers analyzed the sequence information in 6.1 million protein-coding genes from around 2,000 prokaryotes - the simplest single-cell organisms, including bacteria and archaea. They wanted to find all the genes whose traces in tribal history can be traced back to LUCA. As the most important result of their work, the researchers present a list of 355 genes that LUCA possessed and that provide information about the way of life and the habitat of LUCA.
The ancestor of all life was anaerobes
From the 355 genes it can be concluded that the common ancestor of all life was an anaerobic, i.e. he did not need oxygen to live. It thrived at temperatures around 100 ° C. It operated its metabolism with the help of carbon dioxide, hydrogen and nitrogen, and met its energy needs from simple chemical reactions without the aid of light. Furthermore, in the metabolism of the common ancestor, evidence was found of an important role played by transition metals such as iron, nickel and molybdenum as well as other elements such as sulfur and selenium. LUCA's metabolism thus had similarities with that of some groups of organisms still alive today, especially with the acetate-forming clostridia (in bacteria) and the methane-forming methanogens (in the ark).
Did life arise at deep sea hydrothermal springs?
The new data support the theory that life originated in deep-sea hydrothermal springs and that the first organisms to live there were autotrophs - organisms that synthesize all of their essential nutrients, such as amino acids and vitamins, from carbon dioxide themselves. Prof. Martin points out the important implications for further investigations: "We have not only discovered a number of original genes, we have also identified the organisms in which these genes occur today." These groups still colonize the habitats today (deep-sea springs and barren Earth's crust) that the researchers found for LUCA.
“Everything speaks for it”, continues Prof. Martin, “that they never left the ecological niche in which life arose around four billion years ago.” Thus, the microbial communities at today's deep-sea sources can get direct insights into the life of the first microbes grant - as if a time machine had transported the original habitat of the first cells into the present. "
Prof. Dr. James McInerney, evolutionary biologist from the University of Manchester, writes in an accompanying comment on the Düsseldorf publication: “These insights into the metabolism of the last universal common ancestor provide insights into the way of life of the organisms that lived before the primal cleavage of the prokaryotes Bacteria and arks came. The new study gives us a fascinating insight into life four billion years ago. "
Search for extraterrestrial life
The study also has consequences for the search for traces of life elsewhere in our solar system. If our cellular ancestors originated from hydrothermal springs, the sun did not play an essential role in the origin of life. Life would have emerged from purely geochemical energy. On Enceladus, one of Saturn's moons, there is evidence of the existence of such geochemical energy in the form of hydrothermal activity. “Whether geochemistry is taking steps towards life there remains an exciting question,” says Prof. Martin. (idw, red)
M. Weiss, F. Sousa, N. Mrnjavac et al .: The physiology and habitat of the last universal common ancestor. Nature Microbiology, July 25, 2016, DOI: 10.1038 / nmicrobiol.2016.116
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