4 research outputs found
Multiflagellarity leads to the size-independent swimming speed of bacteria
Flagella are essential organelles of bacteria enabling their swimming
motility. While monotrichous or uniflagellar bacteria possess a single
flagellum at one pole of their body, peritrichous bacteria grow multiple
flagella over the body surface, which form a rotating helical bundle propelling
the bacteria forward. Although the adaptation of bacterial cellular features is
under strong evolutionary pressure, existing evidence suggests that
multiflagellarity confers no noticeable benefit to the swimming of peritrichous
bacteria in bulk fluids compared with uniflagellar bacteria. This puzzling
result poses a long-standing question: why does multiflagellarity emerge given
the high metabolic cost of flagellar synthesis? Contrary to the prevailing
wisdom that its benefit lies beyond the basic function of flagella in steady
swimming, here we show that multiflagellarity provides a significant selective
advantage to bacteria in terms of their swimming ability, allowing bacteria to
maintain a constant swimming speed over a wide range of body size. By
synergizing experiments of immense sample sizes with quantitative hydrodynamic
modeling and simulations, we reveal how bacteria utilize the increasing number
of flagella to regulate the flagellar motor load, which leads to faster
flagellar rotation neutralizing the higher fluid drag on their larger bodies.
Without such a precise balancing mechanism, the swimming speed of uniflagellar
bacteria generically decreases with increasing body size. Our study sheds light
on the origin of multiflagellarity, a ubiquitous cellular feature of bacteria.
The uncovered difference between uniflagellar and multiflagellar swimming is
important for understanding environmental influence on bacterial morphology and
useful for designing artificial flagellated microswimmers.Comment: 23 pages, 4 figure