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As part of our chasis characterisation process, we have decided to model B. subtilis motility. In order to do this, the approach illustrated below was taken. The first phase of modelling involved data collection using microscopy techniques and cell tracking. Collected data was then analysed using algorithms which enabled us to extract distributions of parameters as defined in our model.
Materials
We used the Zeiss Axiovert 200 inverted microscope and Improvision Volocity acquisition software. This system offers a full incubation chamber with temperature control and a highly sensitive 1300x1000 pixel camera for fast low-light imaging. Video images are captured into memory by the system at a basal video frame rate of 16.3Hz. This can be further increased to 27.9Hz by performing x4 binning.
Method
We manually tracked motile B. subtilis, obtaining two-dimensional coordinate data points which describes by the trajectory of the cells. The open source tracking software can be found [http://rsbweb.nih.gov/ij/plugins/track/track.html here].
The coordinate data obtained was then fed into algorithms to model cell trajectory and motility.
Motility Model
The following mechanical model was developed.
In this model, we attempt to obtain a distribution for the flagellar force, which is represented by parameter A. We assume that the medium is homogenous and the drag coefficient is constant throughout the medium, hence the distribution of flagellar force will be sufficiently be described by parameter A.
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