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Chemical inactivation of a bacterial immune system de-domesticates a temperate phage and promotes its spread

Yanyao Cai1, Jaka Jakin Lazar2, Yun Shi3

  • 1Department of Chemistry, Indiana University, Bloomington, IN 47405, USA.

Biorxiv : the Preprint Server for Biology
|May 25, 2026
PubMed

Insights

Researchers identified chemical inhibitors for SpbK, an antiphage defense system in Bacillus subtilis. Inhibiting SpbK releases phages, revealing new insights into mobile genetic element competition and immune signaling.

Area of Science:

  • Microbiology
  • Molecular Biology
  • Genetics

Background:

  • Mobile genetic elements (MGEs) control microbial community behaviors and compete with each other.
  • Anti-phage immune systems, often encoded by MGEs like integrative and conjugative elements (ICEs), regulate MGE spread.
  • The significance of different MGE interference mechanisms remains largely unknown.

Purpose of the Study:

  • To investigate the role of SpbK, an antiphage defense system in Bacillus subtilis ICEs, in controlling phage dissemination.
  • To develop chemical inhibitors to probe inter-MGE competition mechanisms.
  • To explore the broader implications of SpbK inhibition for TIR-domain enzyme function.

Main Methods:

  • Discovery and application of chemical inhibitors targeting the SpbK protein.
  • Experimental analysis of SPβ phage escape and lysogenization dynamics in Bacillus subtilis.
  • Characterization of SpbK's inhibition mechanisms and its relation to TIR-domain enzymes.

Main Results:

  • Chemical inhibition of SpbK significantly enhanced the escape and dissemination of SPβ phages.
  • SpbK's inhibition by chemical compounds revealed two distinct mechanisms.
  • SpbK was identified as a Toll/interleukin-1 receptor (TIR)-domain containing enzyme.

Conclusions:

  • Inhibiting SpbK releases temperate phages, demonstrating its role in phage domestication.
  • The developed inhibitors provide a tool to study inter-MGE competition and phage-host dynamics.
  • Understanding TIR-domain enzyme inhibition may have broad applications in phage therapy, plant immunity, and animal signaling.

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