The ‘single most phenomenal event in the history of life on the planet’, a moment which amounts to Nature’s ‘Big Bang’, has been successfully identified for the first time in ground breaking work by a team of researchers led by Maynooth University ’s Department of Biology.
Approximately two billion years ago, two single cell biological organisms – prokaryotes - neither of which had a true nucleus, fused together to create a new entity, a eukaryote which had a nucleus. The eukaryote is the basic building block which in turn gave rise to all multi-cell organisms we know today – insects, plants, animals, and of course humans.
This was a remarkable event, which appears to have happened only once.  These two primitive single cell life forms came together in an event that essentially allowed nature to grow big.  It is in the nucleus that we find the DNA of all species, and for years it had been a puzzle as to how the first nucleus was created.  Now we know”, said Dr James McInerney of the Bioinformatics and Molecular Evolution Unit of the Department of Biology at Maynooth University, who collaborated with Dr James Cotton at the world famous Sanger Institute in Cambridge.  Their work has just been published in the eminent Proceedings of the National Academy of Sciences, USA.
The Maynooth University team has been working on this research for over 10 years and the work was made possible by the sequencing of the yeast genome in 1997.  Yeast is a model system for molecular biology and the team showed that it contains one eukaryote genome, which came from two distinct, different prokaryote genomes.  “Essentially you had a chimaeric organism, like the Minotaur in ancient Greece, and   this is, in biological terms is what we hypothesised was the common ancestor of all Eukaryotic life.  Because humans are eukaryotes, we were, in essence, trying to trace the deepest human ancestor”, said Dr McInerney.
The team then took the genome sequences of hundreds of species of prokaryotes and eukaryotes and using the Maynooth University High Performance Computing System and the Irish Centre for High End Computing ran tests to see if there were parts of the eukaryote genomes with equivalent parts in the prokaryote genomes.  They found lots of communality between the two groups. 
The team found that the two prokaryotes that came together to form the eukaryote, the eubacteria and the archaebacteria, did so in a ratio of approximately 2:1.   But, while they were fewer in number, the archaebacteria are much more important to the eukaryote as they produce more protein, interact with more genes and therefore seem to be the drivers of alliance with other cells.
“We are pretty sure this profound event only happened once, as we can now analyse the DNA family trees of any Eukaryote and they seem to come back to this shared common ancestor”, said Dr McInerney, adding that it was ‘an open question’ whether the original fusing had happened by accident or was always likely to happen at some time.
Dr McInerney’s lab is currently working on developing an understanding of lateral gene transfer (LGT) – a process where DNA is transferred between species.  This occurs frequently in nature and science is trying to understand the conditions required to make it successful. 
The team’s work has many applications in biotechnology research and the understanding of cloning technology.  “The 21st Century will be known as the century of biotechnology and the use of biological entities – enzymes, genes and species – in order to make new products.  There are billions of dollars being spent every year in finding new combinations of genes that are useful.  It makes sense to learn from Nature – discover out what has already worked safely, and why”, said Dr McInerney.
This research is funded by Science Foundation Ireland (SFI) and the Irish Research Council for Science, Engineering and Technology (IRCSET), now part of the Irish Research Council.