On the expansion of bacteria through soft agar

Condensed Matter lunchtime seminar

On the expansion of bacteria through soft agar

  • Event time: 1:00pm
  • Event date: 30th April 2007
  • Speaker: Ottavio Croze (University of Edinburgh)
  • Location: Room 2511,

Event details

Agar is a polysaccharide gel derived from seaweed which is routinely used for the culture of bacteria. Growth plates consist of a nutrient broth mixed with high concentrations of agar (10-20 g/litre) resulting in a 'hard' gel on which bacterial colonies grow. When investigating the swimming and chemotactic** behaviour of bacteria it is however customary to use 'soft' low concentration (1-3.5 g/litre) agar gels. In such 'motility assays' the centre of soft agar Petri dishes is seeded with a drop of bacterial culture and incubated at constant temperature. The initial bacterial colony then expands across the plate producing stunning patterns. Biologically, the spreading is an easy way to assess motile dysfunction; further, the spatial separation afforded by the spreading allows to select for more or less motile/chemotactic bacteria. Physically, however, one would like to find out how the spreading occurs in the first place. In particular, given that the bacteria have to make their way through a gelatinous network, what is the influence of the agar concentration on the colony expansion speed? I will discuss possible answers suggested by the results of macroscopic experiments I have performed, as well as some very preliminary microscopic investigations.

**chemotaxis: the ability of bacteria to direct their motion towards chemically favourable environments (and away from toxic ones!).

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.