Spatially controlled activity of light-driven E. coli suspensions

Condensed Matter lunchtime seminar

Spatially controlled activity of light-driven E. coli suspensions

  • Event time: 1:00pm
  • Event date: 8th February 2016
  • Speaker: (School of Physics & Astronomy, University of Edinburgh)
  • Location: Room 2511,

Event details

Suspensions of swimming bacteria, such as Escherichia coli, are widely used as model active colloids. But the swimming speed of bacteria normally cannot be easily tuned. However, E. coli can be genetically modified to swim only when illuminated with green light, potentially giving biological active colloids with an externally tuneable speed v.

We studied several mutants of E. coli for which their swimming speed can be controlled by the intensity of incident green light and we specially engineered mutants which adjust their speed rapidly in response to changes in intensity. By projecting intensity patterns of light onto a suspension of such bacteria we are then able to spatially control the activity of these suspensions over large length-scales (~1 mm).

In order to characterise our active suspensions we introduce a spatially resolved version of Differential Dynamic Microscopy. This allows us to extract key parameters, e.g. swimming speed v, relative changes in local cell density ?/?0 and the fraction of non-motile cells ?. We compare our quantitative findings with theoretical predictions that the local density is inversely proportional to the swimming speed.

This is a weekly series of informal talks given primarily by members of the soft condensed matter and statistical mechanics groups, but is also open to members of other groups and external visitors. The aim of the series is to promote discussion and learning of various topics at a level suitable to the broad background of the group. Everyone is welcome to attend..

Find out more about Condensed Matter lunchtime seminars.