Achilles Heel: Type VII Toxin/Antitoxin System Hha/TomB Facilitates Phage Infection by Regulating Cryptic Prophage Lytic Genes

Hha/TomB, a type VII toxin/antitoxin system in Escherichia coli, facilitates infection by 12 BASEL lytic phages, including phage 48, by activating cryptic prophage lytic genes.

• Why it matters: Toxin/antitoxin loci are usually linked to blocking phage infection, but this work addresses whether a type VII system can instead support lytic entry.
• What they did: The authors show that toxin Hha regulates cryptic prophage lytic genes, while antitoxin TomB masks Hha activity by oxidizing a conserved Hha cysteine residue.
• The result: By activating cryptic prophage lytic genes, Hha increases phage infection, suggesting an Achilles heel that lytic phages can exploit rather than a defense mechanism.

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