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0Researchers have identified a bacterial immune mechanism called Metis that detects viral attacks by monitoring host genome destruction. When phages break down bacterial DNA into individual parts, they release a specific methylated mononucleotide known as m6dAMP. This molecule serves as a signal for the Metis system to trigger an abortive infection process, effectively sacrificing the host to prevent the virus from spreading to the rest of the colony. One version of this defense works by depleting NAD+ levels, while another utilizes a membrane-spanning protein to stop viral replication. To avoid accidental activation during routine DNA repair, bacteria use an enzyme called MisB to clear away low levels of these modified nucleotides. Ultimately, this discovery highlights a sophisticated way bacteria use epigenetic modifications to distinguish their own degrading genetic material from normal cellular activity.
References:
Osterman I, Hurieva B, Moses S, et al. Bacteria sense virus-induced genome degradation via methylated mononucleotides[J]. Science, 2026: eaed6782.
