Researchers have discovered a form of DNA modification not previously known to occur in nature. Lab scientists often use the addition of sulfer to the DNA sugar-phosphate backbone to make the DNA resistant to nucleases (DNA-cutting enzymes) in order to use the DNA for other (i.e. theraputic) purposes. This was assumed to be something invented by scientists. IT turns out that bacteria do something like this in nature.
From an MIT press release:
... [researchers] were surprised to discover that a group of bacterial genes, known as the dnd gene cluster, gives bacteria the ability to employ the same modification on their own.
"It turns out that nature has been using phosphorothioate modifications of DNA all along, and we just didn't know about it," ...
The discovery raises many new questions.
"To find that bacteria do it naturally opens up a whole new set of issues to deal with," researcher Dedon said. "What is it doing? Why would bacteria conserve this system which requires five enzymes, each with different co-factors?"
He theorizes that the modification system might serve as either protection against foreign (unmodified) DNA, or as a "bookmark" to assist with transcription or replication of DNA.
The researchers found that the sulfur was incorporated as a phosphorothioate about every several thousand base pairs in the bacterial genome, but they are not sure why it appears in those specific locations. They found the sulfur in many different strains of bacteria, and they believe the gene cluster can be passed between bacteria, much like genes for antibiotic resistance.
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