Original title: Multiflagellarity facilitates bacterial upstream motility
Ran Tao, Nathaniel C. Esteves, Wanho Lee, Lauren Altman +7 · September 2026
Bacteria that infect organs like the lungs, intestines, and urinary tract must swim against moving fluids to spread and colonize surfaces. Scientists wanted to know how bacterial shape and flagella—the tiny, tail-like propellers cells use to move—help them swim upstream. Researchers tested different species against flowing fluid. They discovered that bacteria covered in multiple flagella easily beat species with just one flagellum. In fact, multi-tailed cells gathered upstream at densities up to five orders of magnitude higher, even though one single-tailed competitor swam three times as fast. Extra and longer flagella keep bacteria pinned close to surfaces. Once there, the flow acts like wind on a weathervane, turning the multi-flagellated cells upstream so they can push forward.
Imagine trying to walk against a strong wind. With one long stick, you can lean into it but might fall. With many short sticks, you can brace yourself from all sides. In this paper, bacteria with many flagella use them like the many sticks to stay near surfaces and turn into the flow, while bacteria with one flagellum are like the single stick, fast but easily pushed back.
Pathogens like E. coli and Salmonella use many flagella to swim upstream against fluid flows in the body, outcompeting faster but single-flagella bacteria like Vibrio. This changes how we think about bacterial infections and could lead to new strategies to prevent surface colonization and disease spread.
The study focuses on a few bacterial species and laboratory flow conditions. It does not establish whether multiflagellarity is universally advantageous across all environments or bacterial types. The mechanisms were inferred from simulations and holography but not directly observed in all cases.
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Multiflagellarity facilitates bacterial upstream motility — Ran Tao, Nathaniel C. Esteves, Wanho Lee et al.
Abstract licence: CC0
Explanation generated by Synthesis from the abstract — it is not the original paper. This is a preprint, so it hasn't necessarily been peer reviewed.