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<p>Bacteria restrict viral replication not only through dedicated defense systems but also by entering physiological states that limit cellular resources, yet how phages overcome such host-imposed barriers remains unclear. The stringent response, driven by the alarmone nucleotides ppGpp and pppGpp, can impose a growth-restrictive state that hinders phage infection in specific phage–host contexts. Here, we show that alarmone signaling constrains bacteriophage T7 infection and that the portal protein Gp8 counteracts this barrier by engaging RelA and SpoT, inhibiting their synthetase activities and suppressing alarmone accumulation. Portal mutations that disrupt this interaction sustain alarmone elevation, delay lysis and impair replication in a manner relieved in alarmone-deficient hosts. Portal proteins from representative coliphages share related stringent-response-linked features, indicating that essential virion components can moonlight as antagonists of host stress physiology and that this mechanism is not unique to T7 and may extend to additional coliphages.</p>

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Phage portal proteins counteract stringent-response–mediated restriction

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年7月11日

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  • Kristina Kronborg,
  • Luokai Wang,
  • Muriel Leandra Schicketanz,
  • Kenn Gerdes,
  • Yong Everett Zhang

摘要

Bacteria restrict viral replication not only through dedicated defense systems but also by entering physiological states that limit cellular resources, yet how phages overcome such host-imposed barriers remains unclear. The stringent response, driven by the alarmone nucleotides ppGpp and pppGpp, can impose a growth-restrictive state that hinders phage infection in specific phage–host contexts. Here, we show that alarmone signaling constrains bacteriophage T7 infection and that the portal protein Gp8 counteracts this barrier by engaging RelA and SpoT, inhibiting their synthetase activities and suppressing alarmone accumulation. Portal mutations that disrupt this interaction sustain alarmone elevation, delay lysis and impair replication in a manner relieved in alarmone-deficient hosts. Portal proteins from representative coliphages share related stringent-response-linked features, indicating that essential virion components can moonlight as antagonists of host stress physiology and that this mechanism is not unique to T7 and may extend to additional coliphages.