Team:Edinburgh/Results/Glycogen2

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Edinburgh iGEM 2008

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Glycogen Assay 2

Background and Aims

This assay was designed to determine qualitatively the effects of our glgC and glgC16 BioBricks^TM on glycogen synthesis. glgC encodes ADP-glucose pyrophosphorylase, which is responsible for the rate-limiting step in glycogen synthesis. Hence, we hypothesised that cells transformed with glgC or glgC16 BioBricks^TM would produce more glycogen than control cells since glgC would be overexpressed. glgC16 is a version of glgC containing a mutation which renders it resistant to feedback inhibition, so it is expected to have the highest activity. Finally, cells should produce more glycogen when grown in a glucose-rich medium.

Procedure (3~4 Oct 2008)

A lac promoter was added to the glgC and glgC16 BioBricks^TM.
JM109 E. coli cells were transformed with...
1. BBa_K118019: lac promoter + glgC BioBrick^TM.
2. BBa_K118020: lac promoter + glgC16 BioBrick^TM.
3. Control: cells containing pSB1A2 with a non-coding BioBrick^TM not expected to have any effect on glycogen production.
Cells were grown overnight in LB and LB+40mM glucose. In all cases, ampicillin (100 mg/l) and IPTG (90 mg/l) were included, and growth was at 37 C with shaking.
Cells were harvested by centrifugation from 1 ml of culture and resuspended in 0.1 ml of iodine reagent (5 mM I2 and 5 mM NaI in water) to test glycogen levels. Cells containing more glycogen would stain a darker brown than cells containing less glycogen.

Results

Results of the assay were as follows:

These results confirm that:

Overexpression of glgC and glgC16 resulted in enhanced glycogen production, especially when cells are grown in a glucose-rich medium.
It is not obvious in the photo above, but cells overexpressing glgC16 stained darker than cells overexpressing unmutated glgC, indicating that the mutation increased glycogen production.