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Characterization by British Columbia iGEM 2011

The GPD promoter (BBa_K517001) and GAL promoter (BBa_K517000) as characterized by their regulation of the expression of a GFP reporter.

FACS Analysis of GFP expression as regulated by GPD and GAL Promoters

FACS Analysis of GFP expression as regulated by GPD and GAL Promoters: S. cerevisiae yeast strains containing either the GPD-GFP or GAL-GFP construct were cultured overnight at 30 degrees Celsius in either YPD (dextrose), SC-raffinose or SC-galactose media. These were diluted 1 in 10 in their respective media and grown for 3 hours at 30 degrees Celsius into log phase. The cells were then spun down and samples were collected at 0 hours. The remaining cells were resuspended in SC-galactose media and left to grow at 30 degrees Celsius for 2 hours. The cells were spun down again and samples were collected at this 2 hour time point. The samples were fixed in paraformaldehyde and sonicated before running them through the FACS machine to determine the GFP expression profiles of each strain at each time point. Each profile was plotted with y-axis as counts of cells and x-axis as amount of GFP reading. The GPD-GFP strain's profile did not vary much over the course of the induction regardless of the media it was originally cultured in. However, the GAL-GFP strain experienced a comparably notable shift in the numbers of cells expressing higher levels of GFP when the strain was shifted into SC-galactose media. This profile shift was stronger when the strain was originally cultured in SC-raffinose instead of YPD (dextrose) media, which is expected since dextrose is known to more strongly repress the GAL promoter.

Fluorescence Analysis of GFP expression as regulated by GPD and GAL Promoters

Fluorescence Analysis of GFP expression as regulated by GPD and GAL Promoters: S. cerevisiae yeast strains containing either the GPD-GFP or GAL-GFP construct were cultured overnight at 30 degrees Celsius in either YPD (dextrose), SC-raffinose or SC-galactose media. These were diluted 1 in 10 in their respective media and grown for 3 hours at 30 degrees Celsius into log phase. The cells were then spun down and samples were collected at 0 hours. The remaining cells were resuspended in SC-galactose media and left to grow at 30 degrees Celsius for 2 hours. The cells were spun down again and samples were collected that this 2 hour time point. The samples were fixed in paraformaldehyde and visualized under a fluorescence microscope under the GFP and DIC settings. Acquired images were then color-combined with red representing DIC and green representing GFP. Microscopy images show that the GPD promoter results in constitutive high expression while the GAL promoter is induced by the shift to galactose media.