Novel pESI-encoded autotransporter adhesin PeaP of epidemic Salmonella strains mediates adhesion, atypical biofilm formation, and poultry colonization

Elpers, L.; Scheisser, B.; Felgner, P.; Koettermann, M.; Drauch, V.; Hess, C.; Koepp, N.; Lueken, L.; Hess, M.; Gal-Mor, O.; Hensel, M.

doi:10.64898/2026.05.20.725250

bioRxiv · 10.64898/2026.05.20.725250

Novel pESI-encoded autotransporter adhesin PeaP of epidemic Salmonella strains mediates adhesion, atypical biofilm formation, and poultry colonization

Elpers, L.·Scheisser, B.·Felgner, P.·Koettermann, M.·Drauch, V.·Hess, C.·Koepp, N.·Lueken, L.·Hess, M.·Gal-Mor, O.·Hensel, M.

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Abstract

Salmonella enterica serovar Infantis (SIN) has rapidly become the dominant serovar in poultry worldwide, a success largely linked to the acquisition of the 285 kb megaplasmid pESI. While pESI-encoded antibiotic-resistance and iron-uptake systems are well characterized, pESI-mediated adhesion mechanisms remain poorly understood. Here we identify a novel pESI-encoded monomeric autotransporter adhesin, designated PeaP (pESI-encoded autotransporter protein), and demonstrate its pivotal role in atypical biofilm formation, interference with motility, and colonization of the chicken host. Biofilm assays revealed that pESI-harboring strain SIN 119944 forms robust biofilms at 37 {degrees}C and 42 {degrees}C, temperatures at which CsgD-dependent biofilm formation is negligible. Deletion of csgD did not impair this phenotype, whereas deletion of peaP abolished high-temperature biofilm development and restored motility to wild-type levels. Proteomic profiling of sessile versus planktonic cells highlighted PeaP as the most abundant pESI-derived protein in the biofilm fraction. AlphaFold-based modelling and negative-stain transmission electron microscopy showed that PeaP comprises a C-terminal {beta}-barrel and a 1,500 aa passenger domain with three tandem repeats, projecting filamentous appendages [~]37-nm from the outer membrane. Antibody blockade of PeaP reduced surface adhesion >6-fold, confirming its adhesive function. In an infection model of 2 day-old chicken, the peaP mutant displayed significantly lower colonization, indicating PeaP-mediated adhesion in vivo. Collectively, pESI-positive SIN deploys PeaP for CsgD-independent, temperature-tolerant biofilm formation and enhanced gastrointestinal colonization, providing a mechanistic basis for the epidemic spread of this multidrug-resistant pathogen in poultry.

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Elpers, L., Scheisser, B., Felgner, P., Koettermann, M., Drauch, V., Hess, C., Koepp, N., Lueken, L., Hess, M., Gal-Mor, O., Hensel, M.. 2026-05-20. Novel pESI-encoded autotransporter adhesin PeaP of epidemic Salmonella strains mediates adhesion, atypical biofilm formation, and poultry colonization. https://doi.org/10.64898/2026.05.20.725250

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