Difference between revisions of "Part:BBa J45995"

Revision as of 19:18, 8 October 2022

Stationary phase dependent GFP generator

BBa_J45995 is a composite part consisting of an Escherichia coli osmY stationary phase promoter (BBa_J45992) and a GFP generator (BBa_E0840). Thus, BBa_J45995 produces fluorescence in stationary phase cultures.

Usage and Biology

See BBa_J45992 for details on the osmY stationary phase promoter.

Sequence and Features

William and Mary iGEM 2022

The 2022 William and Mary iGEM team created two composite parts to improve part BBa_J45995. One of our parts is BBa_K4174001 and the other is BBa_K417002. Like BBa_J45995, these parts use an osmY promoter, which is induced by the host cell's entry into stationary phase. In typical E. coli cells, osmY, which helps cells transition into stationary phase when under osmotic or metabolic stress, is not produced during exponential growth phase but is produced during stationary phase. Specifically, the osmY promoter is induced by the rpoS (ribosome polymerase sigma S) at the onset of stationary phase (Chang 2002). In part BBa_K4174001, this promoter is partnered with a mRFP1 coding region, and this construct fluoresces red once the host cell has entered stationary phase. In part BBa_K417002, this promoter is partnered with a sfGFP coding region, and this construct fluoresces green once the host cell has entered stationary phase. More information about the design of each of these parts can be found below.

BBa_K417001 Design & Testing
• This composite part is an improvement of the 2006 MIT iGEM team's composite part BBa_J45995, which is a stationary phase detector utilizing osmY. We have replaced GFP with mRFP1 from Mutalik et al. 2013 and added UNS1 and UNS10 sequences to the ends.
• We elected to use monomeric red fluorescent protein 1 (mRFP1) as opposed to the original GFP, as it allows for the construction of an alternative fluorescent reporter.
• We added UNS1 and UNS10 sequences to make this part compatible with Gibson Assembly with our pSB1C3 backbone, as we also added UNS1 and UNS10 to our backbone.
• We also designed a similar green fluorescence system using sfGFP. For more information about this, visit parts page BBa_K4174002.

To test the effectiveness of our improved parts, our team grew the original MIT 2006 construct, our improved sfGFP construct, and our improved RFP construct in E. coli NEB5α in a plate reader. They were grown at 37°C using continuous shaking. For green fluorescence, we used an excitation value of 485 and an emission value of 528. For red fluorescence, we used an excitation value of 584 and an emission value of 610. The values for green fluorescence are reported below. For information about red fluorescence, see parts page BBa_K4174001.

As seen in the graph above, both the sfGFP and MIT GFP constructs enter stationary phase right before 14 hours, but our improved sfGFP circuit is much more fluorescent. The other constructs are our RFP construct and untransformed E. coli cells, both of which serve as negative controls for green fluorescence.

As seen in the image above, qualitative results reveal that our improved constructs are more fluorescent than the original construct. Here, sfGFP is on the far right, and is visibly more brightly green that the original GFP construct.