Bacterial natural transformation by highly fragmented and damaged DNA

Short and damaged DNA is ubiquitous in most environments and can survive more than half a million years. We show that naturally competent environmental bacteria can take up such degraded DNA and incorporate it into their genomes, including DNA from a 43,000-y-old woolly mammoth bone. The process occurs as part of cellular DNA replication and may resemble the earliest forms of horizontal gene transfer. Our findings suggest that natural genetic exchange of DNA from dead and even extinct organisms to contemporary bacteria can take place over hundreds of thousands of years. Hence damaged and degraded DNA may be a previous unrecognized driver of bacterial evolution with implications for evolutionary theory.