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Blue Light Receptor: Planning

Goal

Purifying the promoter region of the blue light receptor from E. Coli. This promotor region than has to be ligated in test-plasmids with GFP or RFP to see how well our promotor responds to blue light.

Required

• E.Coli strain ( MC4100)
• Primers (1) for PCR: already ordered (nummers: 2171 (FP) - 2172 (RP))
• GFP with RBS and Terminator sequence
• Reference plasmids so we can check the strength of the promotor.

Where from

• Strain: from lab
• Primers: self made and ordered
  • For PCR
    • Forward: CATCAT GAATTCGCGGCCGCTTCTAGAG TTT GAC AGG TTC GTC GTC
    • Reverse: CTGCAGCGGCCGCTACTAGTA CCT CTG TTA AAA ATG TTA ATC AAT GTT AAG
• The GFP () came from the freezer (-80) at the lab

Steps

1. PCR reaction to purify suspected promoter region. Probably includes a promoter, RBS and SpeI restriction site.
2. Partial digestion with SpeI. Afterwards, run an agarose gel to identify the correctly cut sequence and then perform a gel extraction. Cut with EcoRI.
3. Cut GFP with EcoRI and XbaI. Couple PCR fragment to GFP. Measure reactivity of the promoter.
4. Cut vector with SpeI and use klenow to create blunt ends. Then ligate the fragments together. Use initial primers to recreate restriction sites and to select correctly ligated sequences. Link to GFP to check the activity of the sequence.
5. “Cleaning” region to strictly promoter. Cutting in different pieces and measuring the GFP activity:

   a.	Same reverse primer, shortening through forward primer.
   b.	Once activity with forward primer ceased, keep it constant and shorten reverse 
   c.	Once promoter found: update those primers with a pre en suffix to make a biobrick out of the promoter

standard promotor test

Important

Following conditions need to be taken into account:

• For growth of the bacteria: 37°C
• For expression of the genes regulated by ycgF/E system: 16°C
• At 16°C: expression will start after 50h and a very slow reversion to the ground state of ycgF
• Working with a colony in the dark and one in light so that the effects of cold temperature on the gene expression pattern can be calculated out.
• Blue light does NOT induce stress and cell death in E. Coli
• To monitor growth of the cells, measurement at OD 578 can be used