Spatial arrangement of several flagellins within bacterial flagella improves motility in different environments

Bruno Eckhardt,Felix K Schmidt,Bina Helm,Laurence G Wilson,Nicola E Farthing,Florian M Rossmann,Kai M Thormann,Marco J Kühn

doi:10.1038/s41467-018-07802-w

Bruno Eckhardt, Felix K Schmidt + Show 6 more

Open Access

https://doi.org/10.1038/s41467-018-07802-w

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Abstract

Bacterial flagella are helical proteinaceous fibers, composed of the protein flagellin, that confer motility to many bacterial species. The genomes of about half of all flagellated species include more than one flagellin gene, for reasons mostly unknown. Here we show that two flagellins (FlaA and FlaB) are spatially arranged in the polar flagellum of Shewanella putrefaciens, with FlaA being more abundant close to the motor and FlaB in the remainder of the flagellar filament. Observations of swimming trajectories and numerical simulations demonstrate that this segmentation improves motility in a range of environmental conditions, compared to mutants with single-flagellin filaments. In particular, it facilitates screw-like motility, which enhances cellular spreading through obstructed environments. Similar mechanisms may apply to other bacterial species and may explain the maintenance of multiple flagellins to form the flagellar filament.

Highlights

Bacterial flagella are helical proteinaceous fibers, composed of the protein flagellin, that confer motility to many bacterial species
Many bacterial species, such as Escherichia coli, harbor a single flagellin gene so that the resulting flagellar filament consists of only one type of subunit
About half of all flagellated bacteria possess more than a single flagellin-encoding gene, and it was demonstrated for several species that their flagellar filament is, assembled from more than one building block

Summary

Introduction

Bacterial flagella are helical proteinaceous fibers, composed of the protein flagellin, that confer motility to many bacterial species. Observations of swimming trajectories and numerical simulations demonstrate that this segmentation improves motility in a range of environmental conditions, compared to mutants with single-flagellin filaments. It facilitates screw-like motility, which enhances cellular spreading through obstructed environments. The flagellins are transported through the filament and assembled at the tip of the growing flagellum[5,6,7] Many bacterial species, such as Escherichia coli, harbor a single flagellin gene so that the resulting flagellar filament consists of only one type of subunit. With the switch to FlaB in the remainder of the flagellin, the cells maintain the ability to wrap the filament around the cell body and execute a screw-like movement[23], which is highly beneficial for spreading through complex environments

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