After an organism is dead its DNA can stick around for hundreds, even thousands of years. But this DNA doesn't always just simply decay - bacteria are capable of recycling it into their own genomes. This does have implications in the evolution of bacteria and the development of antibiotics. Recent research has revealed that bacteria can even use the DNA of organisms that are long dead, and even these ancient snippets pass by the bacterium’s normal DNA proofreading mechanism. Lead author Søren Overballe-Petersen from the Centre for GeoGenetics at the Natural History Museum of Denmark published these results this week in the Proceedings of the National Academy of Sciences.
The bacteria aren’t just taking up the fragments of DNA - they're putting it to use. Because they are able to alter genomes based on found genetic material researchers may have to account for that when developing antibiotics. The study showed that the bacteria can pick up DNA from dead organisms, as even modern bacteria picked up genetic fragments from a woolly mammoth that has been dead for over 40,000 years, which is much older than was previously believed to be possible. This study also helps us understand the earliest stages of evolution on Earth. While scientists have speculated that this was a driving factor in early life, the researchers have now backed up computer modeling to show how DNA recombination could have happened without recA, a protein involved in DNA replication.
As far as the bacteria is concerned, the process is not perfect. While there is the chance that they will find some DNA that will help code for some evolutionary advantage, they could just as easily snag something that could kill them. There is also the possibility for the bacteria to pick up a pathogenic sequence which could pose considerable risks if it enters a water supply or spreads around a hospital. Because the consequences of the new DNA are unknown until it gets translated into protein, the bacteria have the potential to take considerable jumps in its evolution.
The bacteria take up the DNA in a process known as transformation in horizontal gene transfer. As the bacteria replicate their DNA, any loose fragments in the environment are integrated into the new genome. This is the most common way for bacteria to introduce new genetic material, as they do not reproduce sexually and do not have the option to mix with another. This process is being described as a "secondary evolution" for the DNA.