Last universal common ancestor more complex than previously thought

Oct 05, 2011

Scientists call it LUCA, the Last Universal Common Ancestor, but they don't know much about this great-grandparent of all living things. Many believe LUCA was little more than a crude assemblage of molecular parts, a chemical soup out of which evolution gradually constructed more complex forms. Some scientists still debate whether it was even a cell.

New evidence suggests that LUCA was a sophisticated organism after all, with a complex structure recognizable as a cell, researchers report. Their study appears in the journal Biology Direct.

The study builds on several years of research into a once-overlooked feature of , a region with a high concentration of , a type of energy currency in cells. Researchers report that this polyphosphate storage site actually represents the first known universal organelle, a structure once thought to be absent from and their distantly related microbial cousins, the archaea. This organelle, the evidence indicates, is present in the three domains of life: bacteria, archaea and eukaryotes (plants, animals, , algae and everything else).

The existence of an organelle in bacteria goes against the traditional definition of these organisms, said University of Illinois crop sciences professor Manfredo Seufferheld, who led the study.

"It was a dogma of microbiology that weren't present in bacteria," he said. But in 2003 in a paper in the , Seufferheld and colleagues showed that the polyphosphate storage structure in bacteria (they analyzed an ) was physically, chemically and functionally the same as an organelle called an acidocalcisome (uh-SID-oh-KAL-sih-zohm) found in many single-celled eukaryotes.

Their findings, the authors wrote, "suggest that acidocalcisomes arose before the prokaryotic (bacterial) and eukaryotic diverged." The new study suggests that the origins of the organelle are even more ancient.

The study tracks the evolutionary history of a protein enzyme (called a vacuolar proton pyrophosphatase, or V-H+PPase) that is common in the acidocalcisomes of eukaryotic and bacterial cells. (Archaea also contain the enzyme and a structure with the same physical and chemical properties as an acidocalcisome, the researchers report.)

By comparing the sequences of the V-H+PPase genes from hundreds of organisms representing the three domains of life, the team constructed a "family tree" that showed how different versions of the enzyme in different organisms were related. That tree was similar in broad detail to the universal tree of life created from an analysis of hundreds of genes. This indicates, the researchers said, that the V-H+PPase enzyme and the acidocalcisome it serves are very ancient, dating back to the LUCA, before the three main branches of the tree of life appeared.

"There are many possible scenarios that could explain this, but the best, the most parsimonious, the most likely would be that you had already the enzyme even before diversification started on Earth," said study co-author Gustavo Caetano-Anollés, a professor of and an affiliate of the Institute for Genomic Biology at Illinois. "The protein was there to begin with and was then inherited into all emerging lineages."

"This is the only organelle to our knowledge now that is common to eukaryotes, that is common to bacteria and that is most likely common to archaea," Seufferheld said. "It is the only one that is universal."

The study lends support to a hypothesis that LUCA may have been more complex even than the simplest organisms alive today, said James Whitfield, a professor of entomology at Illinois and a co-author on the study.

"You can't assume that the whole story of life is just building and assembling things," Whitfield said. "Some have argued that the reason that bacteria are so simple is because they have to live in extreme environments and they have to reproduce extremely quickly. So they may actually be reduced versions of what was there originally. According to this view, they've become streamlined genetically and structurally from what they originally were like. We may have underestimated how complex this actually was."

Explore further: Life's extremists may be an untapped source of antibacterial drugs

More information: "Evolution of Vacuolar Proton Pyrophosphatase Domains and Volutin Granules: Clues Into the Early Evolutionary Origin of the Acidocalcisomes," Biology Direct.

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User comments : 11

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BradynStanaway
5 / 5 (2) Oct 05, 2011
Amazing!!!
rubberman
2.5 / 5 (2) Oct 05, 2011
Very cool. Considerable ramifications when considering the search for life elsewhere in the solar system as far as what trace elements are present where life may have been.
Callippo
2 / 5 (2) Oct 05, 2011
Fred Hoyle and many others believed in panspermia events and maybe we are facing new indicia of it. On the other hand, we already know, many ontogenetic paradigms were developed and implemented with evolution multiple times during history. Maybe we just didn't find the very first case of organelles in phylogenetic tree.

http://www.panspermia.org

From thermodynamical model follows, the increased complexity connected with nested levels of organels correspond the fast paced changes in life conditions. But evolution is blind and when conditions don't change for sufficiently long time, many complex evolutionary features evolved will recede again. For example, the sharks or bacteria aren't influenced with life environment changes too much, so they can keep the luxury of being simple, effective and "primitive".
Peteri
4.6 / 5 (7) Oct 05, 2011
Interesting article. I suspect that early on in the evolution of life there were many "experimental" prototype cellular systems that co-evolved and, over time, mixed together and swapped components with each other. The most efficient components were then retained by process of selection.

These populations of primitive cells became once again physically isolated, evolved a bit more, re-mixed, swapped components, and so on, many times until we got the final dominant LUCA (or 3 very closely related ones) that split into the bacteria, archaea and eukaryotes.

Just sitting here counting down the minutes until the numb-skull creationalists find this article and post their usual uneducated drivel...
PinkElephant
3.8 / 5 (4) Oct 05, 2011
"This is the only organelle to our knowledge now that is common to eukaryotes, that is common to bacteria and that is most likely common to archaea," Seufferheld said. "It is the only one that is universal."
It may have been the only (known) common organelle, but statements such as
Many believe LUCA was little more than a crude assemblage of molecular parts, a chemical soup...
are overlooking the largest and most obvious common structure: the cell membrane. I think it very unlikely that the LUCA had not even a rudimentary semi-permeable cell membrane, allowing nutrients to pass in, and waste to be expelled -- that absent such a structure the LUCA could differentiate into 3 distinct domains, and that each of those then independently evolved its own cell membrane from scratch.

I'd rather place my bet on an "ancestral cell" as a LUCA, thank you very much.
Deesky
4 / 5 (9) Oct 05, 2011
Fred Hoyle and many others believed in panspermia events and maybe we are facing new indicia of it.

I fail to see how this research has anything at all to do with panspermia.

Musing about panspermia is a waste of time, IMO, as you're basically excluding any further research on the Terrestrial origin of life by moving the goalposts to somewhere (where?) else. In the end, you need to address how life first formed and there is absolutely nothing to suggest that it could not have formed here - nothing.

This is great research. I love the idea of bacterial genetic streamlining.
Deesky
3.5 / 5 (6) Oct 05, 2011
I think it very unlikely that the LUCA had not even a rudimentary semi-permeable cell membrane, allowing nutrients to pass in, and waste to be expelled

Indeed, having a barrier of some kind is surely vital. I have read that in lieu of a 'modern' cell membrane early on, other mechanisms would have substituted.

A theory gaining currency is that naturally occurring lipid-like molecules are capable of forming stable membranes. These lipid membranes have an organizing effect on other molecules that helps small molecules join together to form longer polymers similar to RNA and DNA.

This organizing effect of membranes is seen when chemical mixtures go through cycles of wetting and drying, as would occur along the margins of pools of hot water on volcanic sites.

Such sites would have been a common environment on the early Earth. Wetting and drying promotes chemical reactions and also causes lipid membranes to form compartments that encapsulate different mixtures of compounds.
Deesky
4 / 5 (4) Oct 06, 2011
Looks like I got me a downranking butt pirate - kaasinees. What a fool!
Dave Johnson
1 / 5 (1) Oct 08, 2011
"In the beginning God..."
Ethelred
3 / 5 (2) Oct 09, 2011
Dave Johnson

If you want to discuss this unsupported unfinished claim of yours perhaps you should SAY SOMETHING else.

Two exact same posts. No follow up, no interaction. And frankly no meaning of any kind under those conditions. Why no meaning?

1 Are you joking?
2 Was it satire?
3 Which god?
4 Can you manage to finish a sentence.

IF that was the god of Genesis then it still has little meaning as it could still be 1 or 2 or you you could actually think a single sentence is somehow going to make Genesis correct instead of mere myth.

Take a chance and SAY SOMETHING WITH MEANING. If you have a point MAKE IT and then SUPPORT IT.

Ethelred
As is you look like a spammer for an anonymous god to sell like some pizza franchise with an a single adherent that ran out of bus stops or Jack Chick tracts to leave at the bus stops.

Ethelred
Ethelred
3 / 5 (2) Oct 09, 2011
but the best, the most parsimonious, the most likely would be that you had already the enzyme even before diversification started
The simplest that is reasonable. IF the enzyme was a major advantage for energy manipulation in early life then it could very well have lead to the extinction of all life without the enzyme. How could the enzyme have evolved in the first place if there was only one kind of organism? UNLESS it happened at the same time or immediately after cell walls evolved. Which seems low probability.

Peteri's idea seems on firm ground to me. Certainly bacteria can swap DNA. If Archea do as well then it could even be that the two had split and then the enzyme was spread from one Kingdom to the other if only by one eating another.

PE
I'd rather place my bet on an "ancestral cell" as a LUCA, thank you very much.
LAST is the key word. The cell wall is more likely FIRST structure. I don't see how there can be an organelle without a cell to retain it.

Ethelred

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