Beaglestana flags novel bacterial DNA
- A new bioRxiv preprint reports that a bacterial anti-phage system called DRT7 makes long, protein-primed palindromic DNA, adding a fresh mechanism to the fast-growing catalog of microbial immune defenses. - The paper says DRT7 couples a reverse transcriptase with a primase-polymerase, then builds alternating poly(A)/poly(T)-rich duplex-like DNA after phage activation, without copying a standard nucleic-acid template. - The finding extends recent work on DRT9, which makes protein-primed poly-dA during phage defense, showing bacteria can build unusual DNA products in several ways (biorxiv.org).
Bacteria can make strange DNA when viruses attack them. A preprint posted April 18 says one defense system, DRT7, builds long palindromic DNA using a protein as the starting point. (biorxiv.org) DNA usually gets copied from another DNA or RNA strand, like tracing text from an existing page. The DRT7 study says this system instead starts synthesis in a protein-guided way and then extends the product into alternating poly(A)/poly(T)-rich tracts. (biorxiv.org) The authors, led by Xin-Yi Song, Yushan Xia and Ning Jia, describe DRT7 as a two-enzyme machine inside one protein. It combines a reverse transcriptase, which usually reads RNA, with a primase-polymerase, which can start new DNA strands. (biorxiv.org) In their model, the reverse transcriptase domain first makes poly(T) without needing a complementary nucleic-acid template. That poly(T) then becomes both primer and template for the primase-polymerase domain to add poly(A), producing fold-back duplex-like DNA. (biorxiv.org) This sits inside a larger story about how bacteria fight phages, the viruses that infect them. Many known systems cut invading DNA, but defense-associated reverse transcriptases use DNA synthesis itself as part of the immune response. (nature.com) (biorxiv.org) A 2025 Nature paper from Stephen Tang, Rimantė Žedaveinytė and colleagues showed that a related system, DRT9, responds to phage infection by making polydeoxyadenylate, or poly-dA, and triggering abortive infection. In that mechanism too, the DNA appears to be protein-primed and guided by a non-coding RNA scaffold. (nature.com) An August 2025 EMBO Journal paper added structural detail for DRT9. That study found DRT9 uses a non-coding RNA, shifts from a tetramer to a hexamer, and preferentially synthesizes poly(dA) during anti-phage defense. (springer.com) The new DRT7 preprint pushes the field in a different direction. Instead of a mainly homopolymer product like DRT9’s poly-dA, it reports a palindromic poly(A)/poly(T)-rich duplex-like product assembled by iterative handoff between two catalytic domains. (biorxiv.org) (nature.com) The paper also says DRT7 provides broad-spectrum anti-phage immunity through abortive infection and can be activated by a phage-encoded putative transcriptional regulator. Because the work is a preprint, those claims have not yet been peer reviewed. (biorxiv.org) Taken together, the DRT7 and DRT9 studies suggest bacteria carry several ways to build unusual DNA as part of antiviral defense. The immediate next step is whether other labs can confirm how often these protein-primed DNA products appear across microbes. (biorxiv.org) (nature.com)
