Meet LUCA: Our Complex Ancestor

The relative of all living things, dubbed the Last Universal Common Ancestor (LUCA), was a sophisticated organism with a complex structure recognizable as a cell, according to a new paper in the journal Biology Direct.

Prior theories have held that this great-grandparent of all living things was little more than a crude assemblage of molecular parts, a chemical soup out of which evolution gradually constructed more complex forms. This latest research suggests that was not the case, although LUCA was not a multi-celled creature.

“LUCA was probably a single celled organism because the extracellular machinery needed for multicellularity was developed in eukaryotes (organisms whose cells contain microstructures) very late in evolution,” lead author Manfredo Seufferheld told Discovery News.

“We do not know its appearance, but we hypothesize it looked very much like an archaeum,” added Seufferheld, who is a professor of crop sciences at the University of Illinois.

The archaea are a group of microorganisms that are somewhat similar to, but genetically distinct from, bacteria. The study builds on research into a once-overlooked feature of microbial cells, a region with a high concentration of polyphosphate.Seufferheld and colleagues Kyung Kim, James Whitfield, Alejandro Valerio and Gustavo Caetano-Anollés made the determinations after studying this region of cells which is a type of energy currency.

Through genetic analysis, including the construction of “family trees,” the researchers demonstrated how this polyphosphate storage site actually represents the first known universal organelle. Such specialized subunits, organelles, were once thought to be absent from bacteria and their distantly related microbial cousins, the archaea.

The evidence now indicates the organelle dates back to LUCA, before the three main branches of the tree of life appeared. It is therefore likely present in the three primary domains of today’s Earthly life. These are bacteria, archaea and eukaryotes (plants, animals, fungi, algae and everything else).

via Meet LUCA: Our Complex Ancestor

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