Bacteria's expanding antiviral arsenal

2026-04-23T14:58:26+00:00
New Capabilities, Status: ongoing

Researchers keep uncovering defense systems bacteria use to fight viruses—and each one is a candidate tool for medicine and gene editing

For billions of years bacteria have fought viruses. Until 2018, scientists could name only a handful of the tools they use—mostly restriction enzymes and CRISPR. The catalog has since grown to more than 150 defense systems, and on April 23 Nature added another: Clover, a bacterial system that starves invading viruses of DNA building blocks without poisoning the bacterium itself.

The new paper solves the control problem that makes this kind of defense workable. An enzyme called CloA destroys deoxyguanosine triphosphate—a raw material viruses need to copy their genomes—but only when it detects a viral signal. A partner enzyme, CloB, produces a small molecule that switches CloA off once the threat passes. Every bacterial defense system described in the past decade has become a candidate gene-editing tool or antibiotic lead; CRISPR began the same way.