Difference between revisions of "Part:BBa K592008:Experience"

[http://2012.igem.org/Team:Uppsala_University Uppsala University 2012]

iGEM Team Uppsala University 2012

Promoter strength

Promoter strenghts in MG1566 and DH5alpha, relative to J23101.

A promoter test was carried out to put synthetic and natural promoters on the same scale. Every promoter was assembled before B0032-SYFP2 (BBa_K864101) in the backbone BBa_K592200 (very similar to the pSB3x5 backbones). The test was performed in E coli expression strain MG1655 and cloning strain DH5alpha, by flow cytometry fluorescence measurements of single cells.

Triplicates of each strain and promoter were inoculated in 2 mL LB media with spectinomycin (50 µg/mL) and grown overnight shaking at 37° C. Samples were equilibrated in PBS solution at 1:160 dilution for one hour, and then measured by a BD Biosciences FACSaria III. 10^5 cells of each sample were individually measured and averaged, with dead and other non-flourescent cells excluded. Promoter strength is noted as fractions of the reference promoter's, J23101, strength in corresponding strain.

The variance in expression between MG1655 and DH5α may depend on the reference J23101. The maximum protein expression may be lower in DH5α, due to its lower fitness resulting in lower expression of SYFP2 in the J23101 construct. Alternatively, the clone with J23101 in DH5α may have been weaker than average, resulting in higher RPU values compared to other DH5α.

LacI repression

The possibility of repression by lacI and induction by IPTG was evaluated in the pSB4C15Iq backbone. Cells grown with IPTG (0.5 mM) had a 100-fold increase of RFP expression, when compared to those grown without. Read about pSB4C15Iq for details.