Deinococcus radiodurans are deep branching bacteria that may retain some remnants of the originally designed cells. The most unusual feature of these bacteria is their incredible ability to survive exposure to massive amounts of ionizing radiation and other extreme physical challenges, something that would have been quite useful for seeding this planet billions of years ago.

The ionizing radiation is typically lethal because it blasts the DNA into fragments and it is extremely difficult for the DNA repair machinery to paste the DNA fragments back together in the correct order. Among humans, exposure to less than 500 rads of ionizing radiation is usually lethal. E. coli are much more resistant, as it usually takes anywhere from 100-200 kilorads to kill them. In comparison, Deinococcus can withstand exposure to more than 1500 kilorads without suffering any deleterious effects. How does Deinococcus do it?

These bacteria do not have a mechanism that prevents their DNA from being damged. On the contrary, the radiation breaks the DNA into 1000s of pieces. Yet within 12-24 hours of this exposure, the DNA is fully repaired. Recent research has clarified the mechanism these bacteria use to put their DNA back together:

Unlike most bacteria, however, D. radiodurans contains multiple copies of its genetic material, which can act as backups for each other, Radman says.

Imagine that a cell’s DNA holds the message “Humpty Dumpty sat on a wall, Humpty Dumpty had a great fall.”

Since the spots where DNA breaks because of radiation or damage are random, each copy of the genetic material will likely have breaks in unique locations.

So if one DNA strand breaks into the split messages “Humpty Dumpty sat on a wall” and “Humpty Dumpty had a great fall,” there’s likely another chunk of material floating around that can bridge the gap.

The material might read “sat on a wall, Humpty Dumpty,” for example.

The bacteria then chemically glue matching pieces together. Once they’re bound, the cells fill in the missing parts of each of the two stuck-together copies, the study shows.

Using such clues, D. radiodurans can piece together all of its DNA in about three hours, even if it was split into hundreds of pieces.

There are two features to this mechanism that echo design. First, the process of bridging the gap to restore the original sequence is essentially the same process that intelligent designers use today when they determine the sequence of genomes. That process is called shotgun sequencing. This is not an example of scientists mimicking the natural world; this is an example of convergence, where intelligent designers came up with a method to determine the sequence of DNA that Deinococcus has been using for billions of years. The difference is that while scientists use computers to string together a representation of the genome, Deinococcus connects real-world DNA fragments together using a battery of sophisticated molecular machines in order to survive.

At this point, some might argue that a designer would have endowed bacteria with an elaborate mechanism that simply protects the DNA from the radiation. But this is where the second echo of design comes into play: this repair process depends, as Radman noted, on “multiple copies of its genetic material.” Deinococcus typically contain 8 to 10 copies of their genome during exponential growth and four copies during stationary phase. It’s these copies that make it possible to “bridge the gap” after they have all been blasted into fragments (since no copy is likely to be split at exactly the same place). However, the multiple copies also speak to front-loading. In essence, the stage is set for evolution through gene duplication and, as I explain in The Design Matrix, gene-duplication is indeed one mechanism a front-loading designer would choose. In other words, a mechanism that endows these bacteria with the ability to survive the harsh reality of the pre-biotic earth would also poise them to evolve and unpack buried designs for the future.