Common ancestor of all wildlife, new research

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Scientists Reveal LUCA – Common Ancestor Of All Living Things On Earth

26 July 2016

Many scientists believe that all living entities on Earth originated from an ancient organism called Luca which stands for the Last Universal Common Ancestor. Now, a team led by William F. Martin of Heinrich Heine University has released a new study which aims to “reconstruct the microbial ecology of LUCA.”

Many scientists believe that all living entities on Earth originated from an ancient organism called Luca which stands for the Last Universal Common Ancestor. The single-celled being likely lived around 4 billion years ago and is thought to have eventually spawned two distinct groups of uni-celled life–bacteria and archaea.

Now, a team led by William F. Martin of Heinrich Heine University has released a new study which aims to “reconstruct the microbial ecology of LUCA.” For the research, they tested 286,514 protein clusters and found that 355 protein families likely descended from the organism. Based on the attributes of this select group, the scientists theorize that Luca was able to withstand hot temperatures and live on hydrogen and carbon dioxide instead of oxygen; it also needed metals to be in the surrounding environment.

These combined attributes seem to indicate that this so-called universal ancestor lived in a habitat similar to a hot and gassy deep-sea vent. Despite the team’s findings, critics point out that additional information is needed to prove where life began.

From Nature Microbiology:

The physiology and habitat of the last universal common ancestor

Published online: 25 July 2016

Abstract

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.

We investigated all clusters and phylogenetic trees for 6.1 million protein coding genes from sequenced prokaryotic genomes in order to reconstruct the microbial ecology of LUCA. Among 286,514 protein clusters, we identified 355 protein families (∼0.1%) that trace to LUCA by phylogenetic criteria. Because these proteins are not universally distributed, they can shed light on LUCA’s physiology.

Their functions, properties and prosthetic groups depict LUCA as anaerobic, CO2-fixing, H2-dependent with a Wood–Ljungdahl pathway, N2-fixing and thermophilic. LUCA’s biochemistry was replete with FeS clusters and radical reaction mechanisms. Its cofactors reveal dependence upon transition metals, flavins, S-adenosyl methionine, coenzyme A, ferredoxin, molybdopterin, corrins and selenium. Its genetic code required nucleoside modifications and S-adenosyl methionine-dependent methylations. The 355 phylogenies identify clostridia and methanogens, whose modern lifestyles resemble that of LUCA, as basal among their respective domains.

LUCA inhabited a geochemically active environment rich in H2, CO2 and iron. The data support the theory of an autotrophic origin of life involving the Wood–Ljungdahl pathway in a hydrothermal setting.