Difference between revisions of "Team:Goettingen/Notebook/reporterSystems May"

1. The two B. subtilis strains 168 and the tryptophan prototroph strain SP1 were grown at different glyphosate concentrations. To identify upregulated protein expression in the presence of glyphosate.

For cultivation, the two strains were inoculated in 4 mL LB medium and incubated overnight at 37°C (200 rpm) The overnight cultures were transferred into 4 mL fresh LB medium and grown for 2 h at 28°C (200 rpm).

Proteins were isolated from cultures by lysing the cells with 50 µL lysis buffer and a Bradford assay was carried out to determine the protein concentration.

Materials for the Bradford assay:

• Bradford solution, 5-fold concentration
• buffer from protein elution

Procedure:

1. Prespare for each portein mixture 3 samples with different concentrations.

   Sample	Reference sample
   800 µL H2O	800 µL H2O
   0.5, 1.0 & 2.0 µL crude extract	no protein but equal volume of buffer
   200 µL Bradford Solution	200 µL Bradford Solution
   Sodium Succinate (30%)	1
   50% glucose	0.5
   (Tryptophan	0.5)
   Ad to 50 mL with sterile water	100

2. After mixing the samples with the protein solutions, the mixtures have to be incubated for 5 minutes at room temperature. Transfer the mixtures and the reference sample to 1.5 mL cuvettes and measure the absorption at a wavelength of 595 nm.

3. Calculate the amount of protein in your sample using the following formula:

                      <img class="article_formula" src="">
   

The protein expression was then further analysed by SDS-PAGE and subsequent silver staining.

The Material

• 6× SDS loading dye (98 C)
• 6× SDS loading dye (98 C)
• 10× Running (PAGE) buffer (98 S)
• 1.5 M Tris-HCl, pH 8.8 (95 B)
• 1.56 M Tris-HCl, pH 6.8 (95 B)
• TEMED/TMEDA (Tetramethylethylenediamine)
• Acrylamide:Bis-Acrylamide (37.5:1, TOXIC!!!)
• APS (Ammonium persulfate, 10 %)
• SDS (Sodium dodecyl sulfate, 10 %)
• Power supply & SDS PAGE devices
• Iso-propanol (100 %)

The procedure

1. Clean the glass plates, combs and mats with ethanol and assemble the glass plate sandwich. Be sure that the plates are well aligned. Place the plates in the casting frame and tighten them. Place the casting frames into the casting stands.
2. Wear gloves for making the gels because acrylamide is a neurotoxin in its unpolymerized form!!! Running gel for denaturing SDS PAGE (enough for 2 gels).

   Components for gel 15 %, 12 %, 10 %

   • H₂O 2.3 mL 3.3 mL 4.0 mL
   • Acryl-Bisacrylamide 30 % 5.0 mL 4.0 mL 3.3 mL
   • 1.5 M Tris-HCl, pH 8.8 2.5 mL 2.5 mL 2.5 mL
   • SDS solution 10 % 0.1 mL 0.1 mL 0.1 mL
   • APS 10 % 0.1 mL 0.1 mL 0.1 mL
   • TEMED 8 µl 8 µl 8 µl

   Stacking gel for denaturing SDS PAGE (5 %; enough for two gels)

   • H₂O 6.83 mL
   • Acryl-Bisacrylamide 30 % 1.3 mL
   • 1.5 M Tris-HCl, pH 6.8 0.87 mL
   • SDS solution 10 % 0.1 mL
   • APS 10 % 0.1 mL
   • TEMED 10 µl
3. Mix the ingredients of the running gel and pour the solution quickly (gel starts to polymerize once TEMED has been added) into the gap between the glass plates. Leave enough room for the stacking gel – appr. 1 cm below the bottom of the comb´s teeth. After a minute you can overlay the solution with iso-propanol or ethanol. This excludes the access of oxygen and plane the surface
4. After polymerization, pour off the iso-propanol and rinse with distilled water. Mix the reagents for the stacking gel and pour it on top of the running gel till the space is completely full. Then insert the comb. No alcohol overlay is needed due to the comb.
5. After polymerization clamp the gel into the electrophoresis apparatus and fill it with running buffer. Remove the comb carefully and use a pipette or syringe to wash the wells with running buffer.
6. The protein samples (up to 15 µl) are mixed with SDS loading buffer (2.5 µl) and incubated for 10 min at 95°C.
7. After heating briefly centrifuge the samples to spin down the condensed water.
8. Then you can apply the samples on a SDS PAGE with a pipette or Hamilton microliter syringe. Do not forget to add molecular weight marker in one lane.
9. Run the gel at 80 V until the front has moved into the running gel. Then you can increase the voltage to 120 V. Run the gel until the running front has reached the bottom of the running gel.
10. Pry the plates apart by using a gel spacer. The gel can then be stained (Coomassie staining, method 56 or Silver staining, method 57) to visualize the separated proteins or processed further (Western Blotting, method 58).

The material

• FA-Fixation solution (98 L)
• Developer (98 M)
• Impregnator (98 N)
• Thiosulfate solution (98 O)
• Stop solution (98 P)
• Ethanol (50 %)

The procedure

The protein bands are stained according to method of Nesterenko et al. (1994). For that purpose, the polyacrylamide gels were incubated on a shaker with the following reagents and in the stated order.

Results

           <img src="">

→ No significant difference in protein expression could be detected.

To produce a reporter system, we needed to identify promoters from genes that are induced upon glyphosate treatment. Our hypothesis is that the promoter of trpE and trpP are induced by glyphosate, as described in the design section (TO DO, link hier einfügen!!!). Therefore, PtrpE as well as two variants of the EPSP-synthase (encoded by aroE were amplified by PCR using primers iGEM2018_25/26 and iGEM2018_27/28, respectively.

Results

In the following figure are the results of the PCR shown.

           <img src="">

The PCR amplification was repeated including PtrpP. The following primer combinations were used.

The following figure shows the results of the PCR.

           <img src="">

Samples from today in addition to the samples on 18.05.18 were purified using the QIAquick PCR Purification Kit. The DNA was eluted in 35 µL H₂O.
Concentration of the purified DNA was measured at the Nanodrop device.

Preparation of competent E. coli strains DH5α and XL1-Blue

The preparation was carried out over the following days.

The Material

• TB buffer (ice-cold)
• liquid LB medium
• SOB medium
• 1 M MgCl₂
• 1 M MgSO₄
• DMSO (100%)

The Procedure

1. Inoculate 20 mL LB medium either with a single colony or from a cryo stock of the desired E. coli strain and incubate the culture with agitation for 20 h at 28°C.
2. Inoculate 250 mL SOB medium supplemented with 10 mM MgCl₂ and 10 mM MgSO₄ in a 2 L shake flask and grow the cells to an OD₆₀₀ of 0.5–0.9 (20–24 h) at 18°C and 200–250 rpm.
3. Incubate the whole flask for 10 min on ice. Collect the cells by centrifugation for 10 min at 4°C and 5,000 rpm. Re-suspend the cell in 80 mL of ice-cold TB buffer and incubate them for 10 min on ice. Collect the cells by centrifugation for 5 min at 5,000 rpm.
4. Re-suspend the cells in 20 mL of ice-cold TB buffer. Add DMSO to a final concentration of 7% (1.4 mL) by gently shaking the falcon tube.
5. Transfer 0.2 mL aliquots into labelled Eppendorf reaction tubes and freeze the cells in liquid nitrogen. Store the cells at -80°C. The volume of the pre-culture strongly depends on the E. coli strain. Using DH5α, it is recommended to use 4 mL pre-culture and inoculate at 8 a.m. Nex day around 10 a.m. this strain should have reached an OD₆₀₀ between 0.5 and 0.6. If you use the strain XL1-Blue, you will need less cells and it is sufficient to inoculate the SOB medium around lunchtime.

We performed a test transformation to prove that the cells were actually competent. The following plasmids were used.

• pBQ200
• pGP172
• pAC7
• pAC5

           <img src="">

The transformed cells were incubated over night at 37°C and the colonies were colony forming units were counted.

4 mL LB medium were supplemented with the appropriate antibiotics and inoculated with the transformed strains (25.05.18). The cultures were incubated over night with agitation at 37°C.

The isolation of the plasmids was performed with the NucleoSpin® kit from Macherey and Nagel.

The Material

• Liquid LB medium
• NucleoSpin® plasmid kit

The Procedure

1. Use single colonies from your transformation plates to inoculate 4 mL (15–20 mL for low-copy plasmids) liquid LB medium supplemented with the appropriate antibiotic and grow the culture overnight at 37°C with agitation.
2. Collect the cells from 1.5 mL (15 mL for low-copy plasmids) of the overnight cultures by centrifugation (1 min, 13,000 rpm). Re-suspend the pellet in 250 mL of buffer A1, add 250 mL of buffer A2, mix gently 6–8 times and incubate the suspension for 5 min at room temperature. For the isolation of low-copy plasmids add 500 mL of buffers A1 and A2 to the cells.
3. Add 300 mL (0.6 mL for low-copy plasmids) of buffer A3, mix gently 6–8 times and centrifuge the lysate for 5–10 min at 13,000 rpm.
4. Transfer the supernatant into NucleoSpin® plasmid column, centrifuge for 1 min at 13,000 rpm and discard the flow-through.
5. OPTIONAL: For sequencing of low-copy plasmid DNA add 500 mL buffer AW to the column, centrifuge for 1 min at 13000 rpm and discard the flow-through.
6. Add 600 mL of buffer A4, centrifuge (1 min, 13,000 rpm) and discard the flow-through.
7. To dry the silica membrane, centrifuge again for 2 min at 13,000 rpm.
8. Add 50 mL of sterile and deionized water on top of the silica membrane of the column incubate the column for 1–5 min at room temperature and elute the DNA by centrifugation for 1 min at 13,000 rpm.
9. The plasmid DNA is highly pure and can be stored at -20°C.

The concentration of the isolated plasmids was determined with the Nanodrop device.

For the cloning procedure, a restriction digest was carried out with aroE_1, aroE_2, PtrpP, and PtrpE fragments (from 18.05.18 and 22.05.18).

Reaction mixtures to digest the fragments

The samples were then purified with the PCR purification clean up Kit and eluted in 25 µL sterile H₂O. The concentrations of the digested fragments were determined using the Nanodrop device.

Reaction mixtures to digest the plasmids

pGP172

The digest was tested on an agarose gel.
Afterwards, the following mixture was prepared.

The digest was finally incubated with 1 µL "Fast AP" for 10 min at 37°C and eluted in 25 µL H₂O.

pBQ200

The digest was tested on an agarose gel.
Afterwards, the following mixture was prepared.

The digest was finally incubated with 1 µL "Fast AP" for 10 min at 37°C and eluted in 25 µL H₂O.

pAC7

The digest was tested on an agarose gel.
Afterwards, the following mixture was prepared.

The digest was finally incubated with 1 µL "Fast AP" for 10 min at 37°C and eluted in 30 µL H₂O.

Concentration of the purified plasmids was analyzed with the Nanodrop device.

In the next step, the fragments and vectors were ligated using 100 ng of the vector and calculating the concentration of the insert dependent on its length.

• pAC7 (10573 bp) → 0.5 µL insert
• pGP172 (4600 bp) → 1.5 µL insert
• pBQ200 (6700 bp) → 1.5 µL insert

Ligation of PtrpP into pAC7

Ligation of PtrpE into pAC7

Ligation of aroE_1 into pGP172

Ligation of aroE_2 into pBQ200

Ligation of Ptrp into pAC7

Re-Ligation of vector pAC7

Re-Ligation of vector pGP172

Re-Ligation of vector pBQ200

All samples were incubated at 16°C over night.

Competent E. coli cells from the strain DH5α were transformed with the ligation samples. Also, a negative controll without DNA was prepared, were the cells received only water. The transformed cells were plated on LB medium agar containing ampicillin and X-Gal in the following manner: on one plate 50 µL and on the second palte 100 µL. The cell were incubated over night at 37°C.