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<p><i>Bacillus thuringiesis</i> infects and kills insect larvae via its spores and associated entomotoxin-containing parasporal bodies (PSBs). We show that endospores and PSBs of <i>B. thuringiensis</i> Sv. Israëlensis are covered in a ‘sporesilk’ matrix that consist of 8 nm wide fibers with a double helical symmetry, formed by protofilaments of stacked alphahelical hairpins. These alpha endospore appendages (‘A-ENA’) are stabilized by up to ten autocatalytic and proximity-induced intermolecular isopeptide bonds per subunit, forming a continuous covalent polymer with remarkable chemical and physical robustness. We show A-ENA functions as <i>B. thuringiensis</i> virulence factor, increasing insecticidal activity by clustering spores and PSBs into an infectious clumps. Moreover, we demonstrate the recombinant production and self-assembly of A-ENA nanofibers, and show that the exogenic addition of A-ENA fibers to <i>B. thuringiensis</i> strains natively lacking sporesilks results in spore-PSB clustering and gain of virulence, enabling the rational, non-GMO functionalization of these biological pest control agents.</p>

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Auto-crosslinking sporesilk fibers promote endospore and Cry toxin clustering

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年3月11日

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  • Mike Sleutel,
  • Adrià Sogues,
  • Han Remaut

摘要

Bacillus thuringiesis infects and kills insect larvae via its spores and associated entomotoxin-containing parasporal bodies (PSBs). We show that endospores and PSBs of B. thuringiensis Sv. Israëlensis are covered in a ‘sporesilk’ matrix that consist of 8 nm wide fibers with a double helical symmetry, formed by protofilaments of stacked alphahelical hairpins. These alpha endospore appendages (‘A-ENA’) are stabilized by up to ten autocatalytic and proximity-induced intermolecular isopeptide bonds per subunit, forming a continuous covalent polymer with remarkable chemical and physical robustness. We show A-ENA functions as B. thuringiensis virulence factor, increasing insecticidal activity by clustering spores and PSBs into an infectious clumps. Moreover, we demonstrate the recombinant production and self-assembly of A-ENA nanofibers, and show that the exogenic addition of A-ENA fibers to B. thuringiensis strains natively lacking sporesilks results in spore-PSB clustering and gain of virulence, enabling the rational, non-GMO functionalization of these biological pest control agents.