Swimming of bacterium \textit{Bacillus subtilis} with multiple bundles of flagella

TL;DR

This study investigates how the number and configuration of flagella in Bacillus subtilis bacteria influence their swimming behavior, revealing that bundle formation is consistent across strains and affects motility.

Contribution

The paper provides new insights into the relationship between flagellar bundle properties and bacterial swimming, showing independence of bundle number from flagella count and linking geometry to motility.

Findings

Number of bundles is independent of flagella count

Most bacteria form three bundles regardless of strain

Swimming speed is anti-correlated with bundle angle

Abstract

We characterize the bundle properties for three different strains of \textit{B. subtilis} bacteria with various numbers of flagella. Our study reveals that, surprisingly, the number of bundles is independent of the number of flagella, and the formation of three bundles is always the most frequent case. We assume that this relates to the fact that different mutants have the same body length. There is no significant difference between the bundle width and length for distinct strains, but the projected angle between the bundles increases with the flagellar number. Furthermore, we find that the swimming speed is anti-correlated with the projected angle between the bundles, and the wobbling angle between the swimming direction and cell body increases with the number of flagella. Our findings highlight the impact of geometrical properties of bacteria such as body length and bundle configuration on their motility.