Team:SDU-Denmark/project-r

Results

Photosensor
The results of the motility assay are just in. In this experiment we shone blue light on one half of the plate, while the other half was in the dark. We then placed one colony in each half and observed their motility pattern after 24 hours. We did this for three different strains of E.Coli - DH5alpha, Wildtype Mg1655 and Mg1655 containing a plasmid with our photosensor constitutively on. See the results for yourself:
Light shone on the right half of the plates, the left half was in the dark.

Mg1655 (Wildtype):

Photosensor (Modified Mg1655)

DH5alpha (Reduced motility):

As you can see, both colonies on the photosensor plate moved towards the darker end of their plate, trying to get awaz from the light. Because of the increased tumbling the colony in the light did not move very far, but the little movement that happened was away from the light. On the dark half, the colony moved alot more, because of the decreased tumbling frequency. This is confirmed by the movement towards the darker edge of the plate.

Video microscopy results: Bacteria containing the photosensor will exhibit a lowered tumbling rate when exposed to blue light (wavelengths around 350nm - 450nm). This was analysed with the help of video microscopy and the open source software "CellTrack". The individual cells trajectory was tracked and their speed measured. The tracking results are as follows:

From left to right, trajectory of: E.Coli with photosensor exposed to blue light, E.Coli with photosensor exposed to red light and E.Coli Mg1655 Wildtype exposed to blue light: (Blue dots show the location of the cell in the given frame, so the number of dots equals the number of frames from the sample.)

The phototaxic bacteria move more in a straight line when exposed to bluelight, as can be seen when comparing the trajectories of the thee bacteria given earlier. These were taken from a batch of 10 cells tracked per sample.

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