Team:Reading/Results
The competition assay yielded bittersweet results. Although the Triple mutant did not outcompete the wild type, and we have plenty of evidence supporting that the wild type Synechocystis will outcompete the Howe triple mutant; see the data section for details. But neither the triple mutant nor the wild type grew on the LB BG-11 plate. This can be put to the fact that Synechocystis are incredibly hard to grow. This can be deemed a success as we aimed for the wildtype to outcompete the Howe mutant, and since neither grew it shows that the Howe mutant poses no serious threat to the environment.
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Fig.1 and Fig.2 compare the absorbance of our Ferricyanide assays at 420nm. At this optical density it allows us to calculate the actual concentration of Potassium Ferricyanide reduced by the electrons produced by the two strains.
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Fig.3 and Fig.4 show the absorbance of the Potassium Ferricyanide at 680nm. These 2 absorbance graphs again show the desired results of that the triple mutant has a greater absorbance than the wildtype in all 3 conditions.
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Fig.5 and Fig.6 show the absorbance of the Potassium Ferricyanide at 750nm. Again these graphs show that the Howe triple mutant has a greater level of reduced Potassium Ferricyanide. The reason why it was aimed for the Triple mutant to have a greater absorbance than the wild type is because Potassium Ferricyanide allows the measurement of activity of the Synechocystis membrane reductases, and as the triple mutant has 3 terminal oxidases deactivated there will be more available electrons to reduce Potassium Ferricyanide. So the higher the absorbance, the more reduced the Ferricyanide ion from the greater levels of free electrons. So this experiment gave us fabulous results!
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Once we had grown enough culture it was time to take out the fuel cell for a test drive. We compared results from the wild type bacteria cultured and the triple mutant (See Fig.7). The results reinforced our initial predictions that the removal of terminal oxidases would help increase the electron output of the cell. Problems encountered here included a lack of a sufficient triple mutant synechocystis resulting in a half full cell. The wild type on the other hand had a full cell although it was still beaten in terms of voltage output by the triple mutant. Both wild type and mutant filled fuel cells were tested under the same conditions. The results generated by the mutant are around equal to the power of a third of a regular battery (see Fig.7 once more).
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