Science Daily carries this story,  http://www.sciencedaily.com/releases/2013/11/131103140259.htm, from University of Nottingham (http://www.nottingham.ac.uk/news/pressreleases/2013/october/life,-but-not-as-we-know-it.aspx), and they reference their paper in Nature, which is of course way too expensive, http://www.nature.com/nature/journal/vaop/ncurrent/full/nature12650.html.

And now for something completely unexpected…

“in some organisms, the replication origins — genetic switches that control DNA replication — are not only unnecessary…”. In other words, they pulled out the chemical switches (machinery) that accomplish DNA duplication, and the things replicated anyway, by an uncontrolled method.

This is basic, but still cool: “Archaea were originally discovered in extreme environments and can survive at very high or very low temperatures, or in highly salty, acidic or alkaline water. They form one of the three distinct branches of life along with bacteria and eukaryotes, which are multi-celled organisms including humans, other animals, plants and fungi. At a genetic level, archaea have been found to be more closely related to eukaryotes, and therefore humans, than to bacteria. The salt-loving Haloferax volcanii being studied by the Nottingham scientists originates from the Dead Sea.” {It seems to me the only thing absolutely essential for life as we have been able to find it so far is liquid water.}

They say, ““The way [these] cells initiate this replication process is to use a form of DNA repair that exists in all of us, but they just hijack this process for a different purpose. By using this mechanism, they kick-start replication at multiple sites around the chromosome at the same time.”” I’m not sure kickstart is the right word. Spontaneous and unhindered (unregulated or without a governing mechanism) seems more in line with what they explain.

From the abstract of the published article, I find this more informative:

DNA replication initiates at defined sites called origins, which serve as binding sites for initiator proteins that recruit the replicative machinery. Origins differ in number and structure across the three domains of life1 and their properties determine the dynamics of chromosome replication. Bacteria and some archaea replicate from single origins, whereas most archaea and all eukaryotes replicate using multiple origins. Initiation mechanisms that rely on homologous recombination operate in some viruses. Here we show that such mechanisms also operate in archaea. We use deep sequencing to study replication in Haloferax volcanii and identify four chromosomal origins of differing activity. Deletion of individual origins results in perturbed replication dynamics and reduced growth. However, a strain lacking all origins has no apparent defects and grows significantly faster than wild type. Origin-less cells initiate replication at dispersed sites rather than at discrete origins and have an absolute requirement for the recombinase RadA, unlike strains lacking individual origins. Our results demonstrate that homologous recombination alone can efficiently initiate the replication of an entire cellular genome. This raises the question of what purpose replication origins serve and why they have evolved. [end quote]

The Nature page includes thumbnails of the figures and a 5MB supplemental data file (Excel spreadsheet).

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