SigA forms amyloid fibrils that associate with the colicin ColE1 to support the antibacterial activity of Shigella sonnei before colonization
Abstract
Shigella sonnei is an enteropathogen that causes bacillary dysentery. During the first step of its virulence cycle, it must outcompete the resident microbiota to establish its own niche.
Here we report that SigA, the sole SPATE (Serine Protease Autotransporter of Enterobacteriaceae) family member in S. sonnei, plays an indirect but central role in this process. A genome-wide analysis showed that the SPATE family includes SigA, Pic, SepA, and Sat. We demonstrated that SigA self-assembles into amyloid fibrils (F-SigA) independently of its protease activity. F-SigA remains associated with the S. sonnei surface in vitro and in vivo. Purified F-SigA fibrils have a diameter of 17.7 ± 3.2 nm, and their amyloid organization was confirmed using specific markers and biochemical methods. F-SigA is secreted into the lumen in vivo and localizes to the surface of the colonic epithelium. We found that colicin E1 (ColE1) interacts with F-SigA amyloid fibrils, and that F-SigA-ColE1 complexes display antimicrobial activity that promotes S. sonnei competition with other bacteria. Because Pic, another Shigella SPATE, also forms amyloid fibrils, we anticipate that this virulence mechanism may be relevant across a wide range of Shigella strains and enterobacteria and may serve additional roles during the Shigella virulence cycle.
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BibTeX
@misc{sabbah2026siga,
title = {{SigA forms amyloid fibrils that associate with the colicin ColE1 to support the antibacterial activity of Shigella sonnei before colonization}},
author = {Ahmad Sabbah and Julie Maucotel and Béatrice Roche and Mathieu Erhardt and Lorine Debande and Charlotte E Chong and Antoine Schramm and Jérémy Fraering and Johana Chicher and Eric Ennifar and Kate S Baker and Benoit S Marteyn},
howpublished = {HAL},
year = {2026},
month = jul,
doi = {10.64898/2026.07.10.736312},
url = {https://hal.science/hal-05762654v1},
note = {CC BY-NC-ND 4.0},
}
RIS
TY - UNPB
TI - SigA forms amyloid fibrils that associate with the colicin ColE1 to support the antibacterial activity of Shigella sonnei before colonization
AU - Ahmad Sabbah
AU - Julie Maucotel
AU - Béatrice Roche
AU - Mathieu Erhardt
AU - Lorine Debande
AU - Charlotte E Chong
AU - Antoine Schramm
AU - Jérémy Fraering
AU - Johana Chicher
AU - Eric Ennifar
AU - Kate S Baker
AU - Benoit S Marteyn
PY - 2026
DA - 2026/07/10
PB - HAL
DO - 10.64898/2026.07.10.736312
UR - https://hal.science/hal-05762654v1
AB - Shigella sonnei is an enteropathogen that causes bacillary dysentery. During the first step of its virulence cycle, it must outcompete the resident microbiota to establish its own niche. Here we report that SigA, the sole SPATE (Serine Protease Autotransporter of Enterobacteriaceae) family member in S. sonnei, plays an indirect but central role in this process. A genome-wide analysis showed that the SPATE family includes SigA, Pic, SepA, and Sat. We demonstrated that SigA self-assembles into amyloid fibrils (F-SigA) independently of its protease activity. F-SigA remains associated with the S. sonnei surface in vitro and in vivo. Purified F-SigA fibrils have a diameter of 17.7 ± 3.2 nm, and their amyloid organization was confirmed using specific markers and biochemical methods. F-SigA is secreted into the lumen in vivo and localizes to the surface of the colonic epithelium. We found that colicin E1 (ColE1) interacts with F-SigA amyloid fibrils, and that F-SigA-ColE1 complexes display antimicrobial activity that promotes S. sonnei competition with other bacteria. Because Pic, another Shigella SPATE, also forms amyloid fibrils, we anticipate that this virulence mechanism may be relevant across a wide range of Shigella strains and enterobacteria and may serve additional roles during the Shigella virulence cycle.
ER -