Team:SDU-Denmark/project-p

From 2010.igem.org

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(Experiment 1)
(Experiment 1)
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Since exposure to blue light should decrease the phototaxic bacterias tumbling frequency, the expected result was that the colony which was placed between the light and dark half of the plate would spread out in the darkness and would not move further when it reached the light. This is counter-intuitive, since decreased tumbling should lead to a longer distance traveled. What happens at the microscopic scale in semisolid agar is that the agar creates a matrix like structure where there are channels through the agar, which the bacteria can swim through. The decrease in tumbling frequency of the bacteria will make it harder for them to find the channels in the agar to swim through, which leads to them being trapped where they were placed. The result is that a colony which shows an increased run time, will look as if it it was non-motile on these plates [[https://2010.igem.org/Team:SDU-Denmark/project-p#References 1]]. Our results showed exactly this; the bacterial culture had spread out to on the dark half of the plate and did not get nearly as far on the half exposed to light. This experiment was done with a normal wildtype MG1655 and a non-motile strain of ''E.coli'', DH5alpha, as controls. As expected these cells did not show anything like the behavior described above, which indicates that the effect stems from the modification to our photosensor bacteria.
Since exposure to blue light should decrease the phototaxic bacterias tumbling frequency, the expected result was that the colony which was placed between the light and dark half of the plate would spread out in the darkness and would not move further when it reached the light. This is counter-intuitive, since decreased tumbling should lead to a longer distance traveled. What happens at the microscopic scale in semisolid agar is that the agar creates a matrix like structure where there are channels through the agar, which the bacteria can swim through. The decrease in tumbling frequency of the bacteria will make it harder for them to find the channels in the agar to swim through, which leads to them being trapped where they were placed. The result is that a colony which shows an increased run time, will look as if it it was non-motile on these plates [[https://2010.igem.org/Team:SDU-Denmark/project-p#References 1]]. Our results showed exactly this; the bacterial culture had spread out to on the dark half of the plate and did not get nearly as far on the half exposed to light. This experiment was done with a normal wildtype MG1655 and a non-motile strain of ''E.coli'', DH5alpha, as controls. As expected these cells did not show anything like the behavior described above, which indicates that the effect stems from the modification to our photosensor bacteria.
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[[Image:Ingeniør1.JPG|200px|Wildtype bacteria (Left half exposed to light, right half exposed to darkness)|thumb|]] [[Image:Ingeniør4.JPG|200px|Phototactic bacteria (Left half exposed to light, right half exposed to darkness)]]
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[[Image:Ingeniør1.JPG|200px|Wildtype bacteria (Left half exposed to light, right half exposed to darkness)|thumb|'''Figure 1''': ''E. coli'' MG1655 exposed to blue light on the left half and to darkness on the right half]] [[Image:Ingeniør4.JPG|200px|Phototactic bacteria (Left half exposed to light, right half exposed to darkness)|thumb|'''Figure 2''': ''E. coli'' MG1655-pSB exposed to blue light on the left half and to darkness on the right half]]
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These results were useable, but not fully conclusive, since there were some non-optimal conditions present in this experiment. We used ambient light instead of pure blue light, and the exposure to light for the multiple samples was not exactly even. Therefore we had to improve our experimental setup and see if we could reproduce these results with a more reliable setup.<br>
These results were useable, but not fully conclusive, since there were some non-optimal conditions present in this experiment. We used ambient light instead of pure blue light, and the exposure to light for the multiple samples was not exactly even. Therefore we had to improve our experimental setup and see if we could reproduce these results with a more reliable setup.<br>

Revision as of 20:33, 26 October 2010