New Model Proposes Metabolic Water Ejection as Alternative Mechanism for Bacterial Motility
Researchers have developed the "murburn model," which proposes that bacteria swim by ejecting metabolic water through their flagella rather than using a rotary motor driven by proton gradients, as the classical model suggests. The new model challenges decades of accepted understanding by addressing thermodynamic and structural concerns with the traditional rotary-motor explanation. The findings could fundamentally reshape understanding of how microorganisms move and may have implications for evolutionary biology and biophysics.
A preprint study on bioRxiv presents a novel mechanism for bacterial motility that diverges significantly from the widely accepted rotary-motor model. Rather than a proton-gradient-driven rotary engine, the murburn model proposes that water produced as a metabolic byproduct is ejected through the basal secretory module and channeled along the flagellar filament's spiral grooves. This ejected flow creates a shear field that induces transverse bending waves, generating thrust through viscous drag without requiring axial rotation, ion gradients, or complex motor proteins. The researchers derive governing equations from first-principles elastohydrodynamic theory and demonstrate that physiologically realistic metabolic water production rates reproduce observed swimming speeds and rotation frequencies while consuming only a small fraction of cellular energy. The model also provides a unified explanation for multiple forms of microbial motility—swimming, tumbling, gliding, spirochete undulation, and archaeal motility—without invoking rotating shafts or ion-gradient coupling mechanisms.
Limitations & open questions
The study is a preprint and has not undergone peer review. The authors acknowledge that their model makes falsifiable predictions to distinguish it from the rotary-motor model, but experimental validation of these predictions is not yet reported. Additionally, the structural analysis relies on existing cryo-EM data; direct experimental confirmation of lateral water transport through the proposed radial canals would strengthen the evidence.
What different sources said
- bioRxivCenter
A parsimonious murburn model for microbial motility connects metabolic water ejection to observable mechanical outcomes
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