A Specific Ancestral Sequence Reconstruction of Flagellin Can Drive Motility in Salmonella enterica but not Escherichia coli
- 1University of New South Wales
Abstract
The bacterial flagellar filament, built from thousands of flagellin subunits, is essential for flagellar motility. Here, we aimed to use ancestral sequence reconstruction (ASR) to generate conservative, ancestral flagellin sequences that surround the divergency point between Escherichia and Salmonella species and tested their ability to restore motility in flagellin deleted Escherichia coli and Salmonella Typhimurium. Only one (N131) out of three candidates restored motility in S. Typhimurium but not E. coli, despite high structural similarity to native FliC/FljB. S. Typhimurium expressing N131 showed reduced motility relative to wild-type Salmonella FliC, alongside increased tumbling frequency. Serial passage across swim plates produced a derivative, N131.10, containing a single flagellin mutation (M144I), with a larger swim ring diameter but also increased tumbling frequency. Comparison of structural interaction networks among the residues of S. Typhimurium LT2 FliC with those of other filament proteins showed that non-motile candidates (N132 and N134) carried substitutions that disrupted key core-domain atomic interactions. These results demonstrate that flagellar filament assembly tolerates only limited sequence variation and that this capacity for tolerance differs between E. coli and S. Typhimurium despite their close phylogenetic relationship.
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BibTeX
@misc{scadden2026specific,
title = {{A Specific Ancestral Sequence Reconstruction of Flagellin Can Drive Motility in Salmonella enterica but not Escherichia coli}},
author = {J. Scadden and J. S. Philip and P. Ridone and Y. Sowa and M. A. Baker},
howpublished = {bioRxiv},
year = {2026},
month = oct,
doi = {10.64898/2026.10.20.760431},
url = {https://www.biorxiv.org/content/10.64898/2026.10.20.760431v1},
note = {CC BY},
}
RIS
TY - UNPB
TI - A Specific Ancestral Sequence Reconstruction of Flagellin Can Drive Motility in Salmonella enterica but not Escherichia coli
AU - J. Scadden
AU - J. S. Philip
AU - P. Ridone
AU - Y. Sowa
AU - M. A. Baker
PY - 2026
DA - 2026/10/20
PB - bioRxiv
DO - 10.64898/2026.10.20.760431
UR - https://www.biorxiv.org/content/10.64898/2026.10.20.760431v1
AB - The bacterial flagellar filament, built from thousands of flagellin subunits, is essential for flagellar motility. Here, we aimed to use ancestral sequence reconstruction (ASR) to generate conservative, ancestral flagellin sequences that surround the divergency point between Escherichia and Salmonella species and tested their ability to restore motility in flagellin deleted Escherichia coli and Salmonella Typhimurium. Only one (N131) out of three candidates restored motility in S. Typhimurium but not E. coli, despite high structural similarity to native FliC/FljB. S. Typhimurium expressing N131 showed reduced motility relative to wild-type Salmonella FliC, alongside increased tumbling frequency. Serial passage across swim plates produced a derivative, N131.10, containing a single flagellin mutation (M144I), with a larger swim ring diameter but also increased tumbling frequency. Comparison of structural interaction networks among the residues of S. Typhimurium LT2 FliC with those of other filament proteins showed that non-motile candidates (N132 and N134) carried substitutions that disrupted key core-domain atomic interactions. These results demonstrate that flagellar filament assembly tolerates only limited sequence variation and that this capacity for tolerance differs between E. coli and S. Typhimurium despite their close phylogenetic relationship.
ER -