IGEM:IMPERIAL/2008/Bioprinter/MotilityModel

Modelling Bacteria Motility

The key question here is, how can we quantify bacteria motility? We know that we should be able to vary light intensity and wavelength along the visible spectrum, and with these, we can turn on and off the clutch mechanism described in the previous section.

The following paper describes the quantification of random motility using individual cell and population scale assays [1]. In a homogenous solution, the random motility coefficient is given by: [math]\displaystyle{ \mu_o\, = \frac {\nu^2\,tau\,}{3(1-cos\theta\,)} }[/math] [1] where [math]\displaystyle{ \mu_o\, }[/math] is the random motility coefficient, [math]\displaystyle{ \nu\, }[/math] is the mean cell swimming speed, [math]\displaystyle{ \tau\, }[/math] is the mean run time and [math]\displaystyle{ \theta\, }[/math] is the turn angle.

Flagellum development

During growth of B subtilis, in the mid exponential phase there exist 2 types of cells. One population with sigma factor D being turned ON, allowing the expression of the flagellum and permitting motility and undergoing cell division. The other population has sigma factor D switched OFF, the cells grow as long non-motile chains. The gene SwrA causes the sigma factor D to turn ON, and so expression of flagellum biosynthesis. Another gene SwrB downstream of SwrA, favours sigmaD directed expression as well. [2]

B subtilis swarms on a solid surface and swims in liquid. However, lab strains are not able to swarm due to their inability to produce surfactant.

References

1. Lewus P and Ford RM. Quantification of random motility and chemotaxis bacterial transport coefficients using individual-cell and population-scale assays. Biotechnol Bioeng. 2001 Nov 5;75(3):292-304. DOI:10.1002/bit.10021 |
2. Kearns DB and Losick R. Cell population heterogeneity during growth of Bacillus subtilis. Genes Dev. 2005 Dec 15;19(24):3083-94. DOI:10.1101/gad.1373905 |