Swimming bacteria power microspin cycles

Alex E. Hamby, Dhruv K. Vig, Sasha Safonova, Charles W. Wolgemuth

Research output: Contribution to journalArticlepeer-review

16 Scopus citations


Dense suspensions of swimming bacteria are living fluids, an archetype of active matter. For example, Bacillus subtilis confined within a disc-shaped region forms a persistent stable vortex that counterrotates at the periphery. Here, we examined Escherichia coli under similar confinement and found that these bacteria, instead, form microspin cycles: a single vortex that periodically reverses direction on time scales of seconds. Using experimental perturbations of the confinement geometry, medium viscosity, bacterial length, density, and chemotaxis pathway, we show that morphological alterations of the bacteria transition a stable vortex into a periodically reversing one. We develop a mathematical model based on single-cell biophysics that quantitatively recreates the dynamics of these vortices and predicts that density gradients power the reversals. Our results define how microbial physics drives the active behavior of dense bacterial suspensions and may allow one to engineer novel micromixers for biomedical and other microfluidic applications.

Original languageEnglish (US)
Article numbereaau0125
JournalScience Advances
Issue number12
StatePublished - Dec 19 2018

ASJC Scopus subject areas

  • General


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