Experiments Overview
See a composite list of the iGEM Guelph 2025 protocols and workflows.
Protocols Overview
Protocols
Molecular Biology Techniques
Golden Gate Assembly
Materials
- PCR Tubes
- Desired Plasmid/DNA
- Desired Type IIS Restriction Enzyme
- HI-T4 DNA Ligase
- T4 Ligase Buffer
- Nuclease Free H2O
- In a PCR tube, add the following reagants in the order listed:
Reagent Amount Nuclease Free Water Up to 20 µL T4 DNA Ligase Buffer 2 µL DNA/Plasmid 1 µL per DNA/Plasmid HI-T4 DNA Ligase 1 µL Type IIS Restriction Enzyme 1 µL - Label PCR tubes with a number and in the lab notebook, create a legend for the contents of each PCR tube
-
Complete the reaction within a thermocycler at the following conditions:
- 42°C for 2 min → 16°C for 5 min (cycle 35X)
- 80°C for 20 min
- Store at -20° C in freezer
For the creation of entry vectors using the MoClo Kit the digestion and heat inactivation steps are omitted, ending the reaction on a ligation as recommended in the supplementary material1.
References- Lee, M.E., DeLoache, W.C., Cervantes, B., and Dueber, J.E. (2015). A Highly Characterized Yeast Toolkit for Modular, Multipart Assembly. ACS Synth. Biol. 4, 975–986. https://doi.org/10.1021/sb500366v.
Digestion Reaction
Materials
- 1.5 mL Microfuge Tube
- P10 Pipette & Tips
- Desired DNA/Plasmid
- Desired Restriction Enzyme
- Restriction Enzyme Buffer
- HPLC H2O
- Label 1.5 mL microfuge tubes accordingly and record in lab notebook
- Add reagents/materials in the amount and order as listed:
Reagent/Material Amount HPLC H2O 4 µL Restriction Enzyme Buffer 1 µL DNA/Plasmid 4 µL Restriction Enzyme 1 µL - Spin down at short/pulse cycle to ensure all contents are at the bottom of the tube
- Incubate at 37°C at one hour on a heat block
- Heat inactivate at 80°C for 10 min
- Store at -20°C
Gel Electrophoresis
Materials
- Gel Electrophoresis Cassette & Lid
- Power Supply
- Casting Tray & Comb
- Red Safe
- Agarose Powder
- 1X TAE Buffer
- DNA Sample
- DNA Ladder
- Loading Dye
(A) Casting 30mL 0.8% Agarose Gel:
- Using a graduated cylinder, measure 30 mL of 1X TAE buffer and pour into a flask
- Using a weighing boat, measure 0.24 g of agarose and add to the flask
-
Dissolve agarose
- Swirl the solution gently to mix
- Microwave in 30-second intervals, swirling between each heating, until the agarose is fully dissolved and no visible crystals remain
- Watch closely to prevent overflow, as the solution can boil over quickly
- Cool Solution
- Allow the flask to cool until it is warm to the touch, but not too hot
- If the gel solidifies prematurely, you can reheat it only if RedSafe has not been added
- Once cooled slightly, add 0.5 µL of RedSafe and swirl gently to mix
- Prepare casting tray
- Use green tape to seal both open ends of the casting tray. Ensure a tight seal by pressing the edges of the cassette against the lab bench
- Insert the comb into the cassette
- Slowly pour the agarose solution into the cassette, avoiding bubbles
- Allow the gel to solidify for about 30 minutes. Once fully set, remove the tape and proceed with gel electrophoresis
- Place the gel tray into the electrophoresis chamber and fill the chamber with 1X TAE buffer until it reaches the "max" line, or the gel is fully submerged
- Ensure the side with the comb is facing the black (negative) electrode
- Gently pull the comb straight up to avoid damaging the wells
- Check that the wells are intact and filled with TAE buffer
- Gel is now ready for sample loading
- Cut a small piece of parafilm. Dispense 2 µL of loading dye for each sample (except the ladder) onto the parafilm
- Add 8 µL of DNA sample to each droplet of loading dye. Pipette up and down gently to mix, avoiding bubbles
- Change tips between each sample
- If the DNA sample being used has a high concentration, use less than 8uL, or the band will appear too bright when imaged
- Pipette 5 µL of DNA ladder into the first well of the gel
- Before loading, map out your sample order to keep track of what is in each well
- Take up 10 µL of your PCR + dye mixture and carefully load it into the wells (be careful not to puncture the gel while loading)
- Change tips between each sample
- Place the lid on the electrophoresis apparatus (black to black, red to red). Turn on the power supply and set it to 120V
- If you see tiny bubbles forming at both ends of the chamber, the run is working
- Wait 30 minutes, then check if the dye has migrated ⅔ of the way down the gel
- The run typically takes ~45 minutes but check at 30 minutes to be sure
- Once done, turn off the power supply and unplug the lid
- Your gel is now ready to be imaged
When microwaving the agarose and TAE, the content and the flask may be hot, ensure proper protection is used such as heat-resistant gloves.
Polymerase Chain Reaction (PCR)
Materials
- PCR Tubes
- Nuclease Free H2O
- 5X Phusion HF Buffer
- 10nM dNTPs
- Forward and Reverse Primers
- Template DNA
- Phusion DNA Polymerase
- Label the PCR tube accordingly and record the materials within the tube in the lab notebook
-
Add the following reagents/components into the PCR tube in the order stated:
Component 50 µL Reaction Final Concentrations H2O Fill to Amount 50 µL 5X Phusion HF Buffer 10 µL 1X 10 mM dNTPs 1 µL 200 µM Forward and Reverse Primer 2.5 µL 0.5 µM Template DNA* Variable 5 ng Phusion DNA Polymerase 0.5 µL 0.02 U/µL -
In the thermocycler complete the following cycling conditions:
Cycle Steps Parameters Amount of Cycles Initial Denaturation 98 °C for 30 sec 1 Denature 98 °C for 10 sec 35 Anneal + Extension 72 °C for 30 sec 35 Final Extension 72 °C for 5 min 1 Hold 4 °C ∞ - For long-term storage keep PCR tubes at -20°C
- Thermo Fisher Scientific. (2016). Phusion™ High-Fidelity PCR Kit User Guide (MAN0013363). https://assets.thermofisher.com/TFSAssets/LSG/manuals/MAN0013363_Phusion_HiFi_PCR_Kit_UG.pdf.
Colony Polymerase Chain Reaction (PCR)
Materials
- PCR Tubes
- Nuclease Free H2O
- Q5 5X buffer
- 10nM dNTPs
- Forward and Reverse Primers
- Template DNA
- Select a microbial colony of interest and set plate aside for collection with pipette tip
- Label the PCR tube accordingly and record the materials within the tube in the lab notebook
-
Add the following reagents/components into the PCR tube in the order stated:
Component 50 µL Reaction DreamTaq Green PCR Master Mix 2X 25 µL Forward and Reverse Primers 2.0 µM Template DNA 1 µg Nuclease Free H2O Fill to Amount 50 µL -
In the thermocycler complete the following cycling conditions:
Cycle Steps Parameters Amount of Cycles Initial Denaturation 95 °C for 3 min 1 Denature 95 °C for 30 sec 35 Anneal 64 °C for 30 sec 35 Extension 72 °C for 1 min 35 Final Extension* 72 °C for 15 min 1 - For long-term storage keep PCR tubes at -20°C
- Thermo Fisher Scientific. (2016). DreamTaq Green PCR Master Mix Product Information (MAN0012704). https://documents.thermofisher.com/TFS-Assets/LSG/manuals/MAN0012704_DreamTaq_Green_PCR_MasterMix_K1081_UG.pdf.
Site Directed Mutagenesis - Polymerase Chain Reaction (SDM-PCR) with Dpn1 Digest
Courtesy of Dr. George van der Merwe.
(A) SDM-PCR:
Materials
- PCR Tubes
- Nuclease Free H2O
- Q5 Polymerase
- Forward and Reverse Primers
- Template DNA
- dNTPs
- Q5 buffer
- Design SDM primers to partially overlap, with the desired mutation located in the middle of each primer
- Label the PCR tube accordingly and record the materials within the tube in the lab notebook
-
Add the following reagents/components into the PCR tube in the order stated:
Component 50 µL Reaction Final Concentration H2O To 50 µL 5X Q5 Buffer 10 µL 1X 10 mM dNTPs 1 µL 1 mM Template DNA Variable 10 ng 25 mM Forward Primer 0.5 µL 0.5 mM 25 mM Reverse Primer 0.5 µL 0.5 mM 2U Q5 Polymerase 1 µL 1 U -
In the thermocycler complete the following cycling conditions:
Cycle Steps Parameters Amount of Cycles Initial Denaturation 95 °C for 3 min 1 Denature 95 °C for 30 sec 20 Anneal 64 °C for 30 sec 20 Extension 72 °C for 1 min 20 Final Extension* 72 °C for 15 min 1 - For long-term storage keep PCR tubes at -20°C
(B) Dpn1 Digest:
Materials
- 1.5 mL Microfuge Tube
- Nuclease Free H2O
- 10X FD buffer
- PCR product
- Dpn1
- Add the following reagents/ components into the microcentrifuge tube in the order stated:
- Spin down in centrifuge on short / pulse cycle to ensure contents are in bottom of tube
- Incubate at 37°C for a minimum of 3.5 hours
- Remove from heat and run on agarose gel, followed by sequencing. For later use, store at –20 °C. Template DNA should be destroyed and product can now be transformed into bacteria
Component | Volume |
---|---|
H2O | 13 µL |
10X FD Buffer | 5 µL |
PCR Product | 10 µL |
Dpn1 | 2 µL |
Miniprep
Materials
- ThermoScientific Miniprep Kit
- P1000 Pipette & Tips
- P200 Pipette & Tips
- 1.5 mL Microfuge Tubes
References
- Lucate, J. (2018). Plasmid DNA miniprep protocol for EZ-10 Spin Column Plasmid DNA minipreps kit (BS413), 50 preps v3. Preprint, https://doi.org/10.17504/protocols.io.n8tdhwn https://doi.org/10.17504/protocols.io.n8tdhwn.
PCR Purification
Materials
- ThermoScientific GeneJET PCR Purification Kit
- P1000 Pipette & Tips
- P200 Pipette & Tips
- 1.5 mL Microfuge Tubes
- PCR Product
References
- Thermo Fisher Scientific. GeneJET PCR Purification User Guide. (MAN0012662). https://documents.thermofisher.com/TFS-Assets/LSG/manuals/MAN0012662_GeneJET_PCR_Purification_UG.pdf.
DNA Cleanup
Materials
- BioBasic EZ-10 Spin Column DNA Cleanup Miniprep Kit
- P1000 Pipette & Tips
- P200 Pipette & Tips
- 1.5 mL Microfuge Tubes
- PCR or GGA Product
References
- BioBasic. (2018). EZ-10 Spin Column DNA Cleanup Miniprep Kit Product Information. (BS367/ BS368/ BS668). https://www.biobasic.com/us/amfilerating/file/download/file_id/28865/
Transformations
E. coli DH5α Competent Cells
- DH5α Competent Cells
- SOC media
- LB plate with desired antibiotic or selective media of choice
- DNA to be transformed
- 1.5 mL Microfuge Tubes
- Ice Bucket
- 42°C water bath
- Shaking Incubator (set to 225 rpm, 37°C)
- Sterile Spreaders (glass or disposable)
- Thaw DH5α competent cells on ice. Chill 1.5 mL microfuge tubes on ice while competent cells thaw
- Once thawed gently mix the cells – pipette up and down
- Aliquot 50 μL of competent cells into chilled 1.5 mL microfuge tubes from (1)
- Add 6 μL of DNA directly into a tube of competent cells. Mix well by gently flicking the tube several times or pipetting up and down
- Incubate cells on ice for 30 minutes
- Heat-shock the cells for exactly 30 seconds in a 42°C heat block
- Do not mix or shake the tube
- Immediately transfer back to ice and incubate on ice for 2 minutes
- Add 250 μL of room temperature SOC recovery media to each transformation tube and mix- pipette up and down
- Shake the tube at 225 rpm for 1 hour at 37°C. Use an empty P10 or P200 pipette tip box and lay microfuge tubes on their side with a piece of table holding all of them in place
- Spread plate all competent cells onto LB + antibiotic plates
- Incubate overnight at 37°C
- Any liquids which have come into contact or was used to inoculate/grow E.coli cells must have 20% bleach added to and let sit for 30 minutes before disposal down the drain and washed with dish soap or detergent
- Any disposable materials which into contact or was used to inoculate/grow E.coli cells can be safely disposed of in the appropriate biohazard waste
- Thermo Fisher Scientific. (n.d.). Thermo Scientific DH5α competent cells [Product catalog page, Catalog No. EC0112]. Thermo Fisher Scientific. https://www.thermofisher.com/order/catalog/product/EC0112
Saccharomyces cerevisiae, BY- strains
(i) Prepare Yeast Culture
Day 1:
- Inoculate 5 mL YPD broth with S. cerevisiae in a sterile 16 mm test tube. One 5 mL culture makes enough cells for 10 transformations
- Incubate overnight at 30°C, shaking at 180 rpm
Day 2:
(ii) Inoculate and Grow Yeast to Mid-Log Phase
- Prewarm 50 mL YPD in a sterile 250 mL flask to 30°C
- Dilute the overnight culture 1/10 or 1/20 in dH2O , and of YPD media, and read OD600. Multiply by dilution factor to determine the actual OD600 of the overnight culture
- Inoculate 50 mL of prewarmed YPD to a final OD600 of 0.2. Use C1V1 = C2V2 to calculate what volume is required for inoculation
- Incubate for 4-6 hours at 30°C, shaking at 180 rpm until OD600 reaches 0.8 - 1.0
- Transfer cells from previous step (5) to 50 mL falcon tubes
- Centrifuge at 3000 * g, room temperature, for 5 minutes, then discard the supernatant
- Resuspend pellet in 25 mL sterile dH2O, centrifuge at 3000 * g, room temperature, for 5 minutes, then discard the supernatant
- Repeat #3, for a total of 2 washes
- Resuspend the final pellet in 1 mL sterile dH2O
- Boil 1 mL of single-stranded carrier DNA for 5 minutes, then immediately place on ice
- Combine desired amount of 50% w/v PEG 3350 and 1.0 M Lithium acetate in a sterile falcon tube. On ice, add desired amount of single-stranded carrier DNA. Mix thoroughly with a pipette
Reagent Volume per plasmid Final Concentration 50% w/v PEG 3350 240 µL 33% 1.0 M Lithium Acetate 36 µL 0.1 M Boiled ss-Carrier DNA (10 mg/mL) 10 µL 0.28 mg/mL Total 286 µL
- Transfer resuspended cells to a 1.5 mL centrifuge tube
- Centrifuge at 8000 * g for 30 seconds, discard the supernatant
- Resuspend in 1 mL sterile dH2O
- Dispense 100 µL of the resuspended cells into separate 2 mL centrifuge tubes
- Centrifuge at 8000 * g for 30 seconds, discard supernatant
- Resuspend the pellet in 286 µL of T Mix
- Add transforming DNA + sterile water to reach a final volume of 74 µL. BY- strains use 0.5 µg of DNA
- Incubate tubes at 42°C for 20 minutes
- Centrifuge at 1000 × g (3000 rpm) for 2 minutes
- Discard the supernatant
- Add 1 mL sterile dH2O, pipette to resuspend the pellet
- Spread 200 µL on SC-URA plates, or another selection plate for desired trait being transformed. Store any remaining yeast suspension at 4°C. Non-transformed yeast cells will lose competency and can be disposed of
- Let liquid soak in, then incubate inverted at 30°C. Colonies should appear in 3-4 days (incubate for 7 days if none appear). Restreak onto the same selective media
- Gietz, R. D., & Schiestl, R. H. (2007). High-efficiency yeast transformation using the LiAc/SS carrier DNA/PEG method. Nature Protocols, 2(1), Article 1. https://doi.org/10.1038/nprot.2007.13
- Gietz, R. D., & Woods, R. A. (2002). Transformation of yeast by lithium acetate/single-stranded carrier DNA/polyethylene glycol method. Methods in Enzymology, 350, 87-96. https://doi.org/10.1016/s0076-6879(02)50957-5
Media
To make all media recipes (excluding Glycerol Stocks), the following equipment is required:
- Scale
- Weight boat
- Scoopula
- Graduated cylinder
- Stir bar
- Stir plate
- Autoclave tape
- Beaker
- Autoclave safe bottle
Luria-Bertani (LB) Media
Materials
- 1L Deionized H2O
- 10g Tryptone
- 5g Yeast Extract
- 5g NaCl
- Optional: 15g Agar or Agarose
- Add 500 mL of dH2O to a beaker with a stir bar and turn stir plate on. Adding reagents directly to water minimizes airborne loss of product
- Weigh out Tryptone and slowly add to beaker
- Weigh out Yeast extract slowly add to beaker
- Weigh out NaCl add to bottle
- Mix until dissolved (low amount of heat may be used to help with this process)
- Pour mixture into a graduated cylinder and add water to 1000 mL, then transfer to bottle
- Lightly tighten bottle lid
- If it is too tight, it will cause an explosion inside the autoclave due to pressure buildup of gases within the bottle
- Label with autoclave tape
- Autoclave at L20
FOR SOLID MEDIA: Pour 20-25ml of autoclaved medium per plate
For Selective Media
Add desired antibiotics or nutritional supplements when the temperature of solution has cooled to 50 °C or lower.
- In an aseptic field, calculate the amount of stock antibiotics needed to achieve the appropriate working concentration using C1V1 = C2V2
- Pipette antibiotics into the bottle of media and gently swirl to completely mix
Antibiotic Working Concentration Ampicillin 100 µg/mL Chloramphenicol 25 µg/mL Kanamycin 50 µg/mL
- Liquid LB Medium with NO bacteria grown can safely be poured down the drain
- Solid LB Medium with NO bacteria grown can be safely thrown away in the garbage
- Apparatus which contains LB medium that has been INOCULATED with any form of microorganism, or which has suspected CONTAMINATION must first be autoclaved before disposal
- Elbing, K. L., & Brent, R. (2019). Recipes and Tools for Culture of Escherichia coli. Current protocols in molecular biology, 125(1), e83. https://doi.org/10.1002/cpmb.83
- Tuttle, A. R., Trahan, N. D., & Son, M. S. (2021). Growth and Maintenance of Escherichia coli Laboratory Strains. Current protocols, 1(1), e20. https://doi.org/10.1002/cpz1.20
Glycerol Stocks
Materials
- Cryovials
- Sterile dH2O
- 100% Glycerol
- Overnight Culture Bacteria
- In the cryovials mix equal parts of 100% glycerol and dH2O to make a 50% glycerol solution
- 0.75 mL of 100% Glycerol
- 0.75 mL of dH2O
- Add 500 µL of the overnight culture to cryovials from (1)
- Ensure vials are adequately labeled and contain all necessary information
- Store at -80°C
- Addgene. (n.d.). Protocol - How to create a bacterial glycerol stock. Retrieved June 10, 2025, from https://www.addgene.org/protocols/create-glycerol-stock/
Overnight Cultures
Materials
- Autoclaved Culture Tubes
- Serial pipette tips and pipette gun
- Desired Antibiotic(s)
- Liquid LB Media, YPD media, or SC-URA Media
- Sterile loop
- Petri Dishes/ Plates of E. coli for Culturing, or Petri Dishes/ Plates of S. cerevisiae for Culturing
- Add 5 mL of appropriate media to culture tube
- For glycerol stocks, add 6 mL
- Add the appropriate amount of antibiotic to each culture tube to achieve the desired working concentration
- Using the formula C1V1 = C2V2
Antibiotic Working Concentration Ampicillin 100 µg/mL Chloramphenicol 25 µg/mL Kanamycin 50 µg/mL - Vortex all culture tubes to thoroughly mix antibiotics and media. Avoid vortexting aggressively to prevent the media from coming in contact with the lid or spilling over
- Using a flame-sterilized loop, pick up the colony being amplified. Tap onto the inside of the glass culture tube. Flame tip to re-sterilize
- Vortex culture tube until the colony has been picked up by the media. Avoid vortexting aggressively to prevent the media from coming in contact with the lid or spilling over
- Incubate at 37°C with shaking at 225 rpm for bacteria, and 30 °C with shaking at 180 rpm for yeast
Discarding Media
- If ANY media has come into contact with bacteria/ microorganisms, or is suspected of being contaminated, add 20% bleach and allow them to sit overnight before discarding down the drain and cleaning culture
- If media has NOT come into contact with any bacteria/ microorganisms discard down the drain and cleaning culture tube
Yeast Peptone Dextrose (YPD) Media
Materials
- 900mL Deionized H2O
- 10g Yeast Extract
- 20g Peptone
- 2% w/v Dextrose/Glucose - prepare from 20% w/v stock solution
- Optional: 15g Agar
- Add 500 mL of dH2O to a beaker with a stir bar and turn stir plate on. Adding reagents directly to water minimizes airborne loss of product
- Weigh out Yeast Extract and slowly add to beaker
- Weigh out Peptone and slowly add to beaker
- Mix until dissolved
- low amount of heat may be used to help with this process
- Pour mixture into a graduated cylinder and add water to 900 mL, then transfer to bottle
- Lightly tighten bottle lid
- If it is too tight, it will cause an explosion inside the autoclave due to pressure buildup of gases within the bottle
- Label with autoclave tape
- Autoclave at L20
- Add 100 mL of 20% w/v Dextrose/Glucose as media is and gently swirl to mix. Do not add Dextrose/ Glucose prior to autoclaving. Autoclaving sugars causes caramelization and the formation of toxic byproducts that can inhibit microbial growth and alter media composition
FOR SOLID MEDIA: Pour 20-25ml of autoclaved medium per plate
Discarding Media
- Liquid media with NO microbes grown can safely be poured down the drain
- Solid media with NO microbes grown can be safely thrown away in the garbage
- Apparatus which contains media that has been INOCULATED with any form of microorganism, or which is suspected of CONTAMINATION must first be autoclaved, before disposal
- Novoprotein. (n.d.). YPD broth preparation. NovoPro Lab Tools. https://www.novoprolabs.com/tools/buffer-preparations-and-recipes/ypd-broth
- DSMZ - German Collection of Microorganisms and Cell Cultures GmbH. (n.d.). Medium 393: YPD medium (liquid or agar) [PDF]. https://www.dsmz.de/microorganisms/medium/pdf/DSMZ_Medium393.pdf
Uracil Dropout Media
Materials
- 900mL Deionized H2O
- 6.7g Yeast Nitrogen Base without Amino Acids
- 1.92g SC-URA
- 2% w/v Dextrose/Glucose - prepare from 20% w/v stock solution
- Optional: 15g Agar
- Add 500 mL of dH2O to a beaker with a stir bar and turn stir plate on.
- Adding reagents directly to water minimizes airborne loss of product
- Weigh out Yeast Nitrogen Base without Amino Acids and slowly add to beaker
- Weigh out SC-URA and slowly add to beaker
- Mix until dissolved
- low amount of heat may be used to help with this process
- Pour mixture into a graduated cylinder and add water to 900 mL, then transfer to bottle
- Lightly tighten bottle lid
- If it is too tight, it will cause an explosion inside the autoclave due to pressure buildup of gases within the bottle
- Label with autoclave tape
- Autoclave at L20
- Add 100 mL of 20% w/v Dextrose/Glucose as media is and gently swirl to mix. Do not add Dextrose/ Glucose prior to autoclaving. Autoclaving sugars causes caramelization and the formation of toxic byproducts that can inhibit microbial growth and alter media composition
FOR SOLID MEDIA: Pour 20-25ml of autoclaved medium per plate
Discarding Media
- Liquid media with NO microbes grown can safely be poured down the drain
- Solid media with NO microbes grown can be safely thrown away in the garbage
- Apparatus which contains media that has been INOCULATED with any form of microorganism, or which is suspected of CONTAMINATION must first be autoclaved, before disposal
Buffers and Solutions
75% Ethanol
Materials
- 95% Ethanol
- MilliQ H2O or ddH2O
- Graduated Cylinder Note: When handling 95% ethanol work in the fume hood
- Using the formula C1V1 = C2V2 determine the amount of stock solution (95% ethanol) required for the desired amount of 75% ethanol
- Fill graduated cylinder with desired amount of MilliQ H2O or ddH2>O
- In the fume hood, add ~150 mL aliquots of 95% ethanol and lightly swirl graduated cylinder to mix the solution – continue adding ethanol until the appropriate volume is achieved
- Fill spray bottles in the fume hood with 75% ethanol, close, and remove. Close the fume hood after use and ensure 95% stock ethanol is stored in a flammable's cabinet Consideration i) Ensure that you are wearing a lab coat and gloves, as 95% ethanol is highly flammable and can irritate the skin upon contact
0.5M EDTA
Materials
- EDTA disodium salt (MW=372.24 g/mol)
- MilliQ H2O
- Sodium Hydroxide (NaOH)
- In a 500 mL bottle dissolve 93.05 grams of EDTA disodium salt in 400 mL MilliQ H2O
- Add stir bar and begin mixing with low-medium heat
- Slowly add ~2.5 grams of sodium hydroxide to EDTA solution until the mixture becomes clear (this is now roughly pH 8)
- When adding the sodium hydroxide allow each addition of ~2.5g to fully dissolve in solution before adding the next batch
- Once a clear solution is achieved check pH with pH stick
- Label and store at room temperature in chemical cabinet
- Behle, A., & Pawlowski, A. (2018, April 6). Recipe for 50x TAE buffer (Version gtvbwn6) [Protocol]. Protocols.io. https://doi.org/10.17504/protocols.io.gtvbwn6
50X TAE Buffer
- Tris-base (MW = 121.14 g/mol)
- Acetic Acid, Glacial
- 0.5M EDTA
- MilliQ H2O
- Graduated Cylinder (Glass 100 mL) Note: This is for 500mL of buffer
- Weigh out 121g of Tris-base and dissolve in 700 mL of MilliQ H2O
- Add 28.5 mL of Acetic Acid, Glacial
- Add 50 mL of 0.5M EDTA
- Add a stir bar and mic on low-medium heat
- Once solution is clear, properly label and store at room temperature in chemical cabinet
- Behle, A., & Pawlowski, A. (2018, April 6). Recipe for 50x TAE buffer (Version gtvbwn6) [Protocol]. Protocols.io. https://doi.org/10.17504/protocols.io.gtvbwn6
1X TAE Buffer
Materials
- 50X TAE Buffer
- MilliQ H2O
- In a 1L bottle measure and add 20mL of 50X TAE
- Add 980 mL of MilliQ H2O
- Cap the bottle tightly and mix by inverting and swirling
- Label and store in the appropriate location within the chemical cabinet
- Behle, A., & Pawlowski, A. (2018, April 6). Recipe for 50x TAE buffer (Version gtvbwn6) [Protocol]. Protocols.io. https://doi.org/10.17504/protocols.io.gtvbwn6
50% Glycerol
Materials
- 99% Glycerol
- MilliQ H2O
- In a beaker with a stir bar, add equal parts 99% glycerol and MilliQ H2O. Turn on stir function and mix till dissolved
- In a sterile field, filter sterilize 50% Glycerol into sterile 50mL falcon tubes
- Label and store in 50 mL aliquots in the appropriate location within the chemical cabinet
20% w/v D-Glucose
Materials
- 20g D-Glucose (Dextrose)
- 100mL MilliQ H2O
- Weigh out 20g D-Glucose and dissolve in 100mL MilliQ H2O
- In a sterile field, filter sterilize 20% D-Glucose into sterile 50mL falcon tubes
- Label and store in 50 mL aliquots in the appropriate location within the chemical cabinet
50% Polyethylene Glycol (PEG) 3350
Materials
- 25g Polyethylene Glycol 3350
- 50mL MilliQ H2O
- Weight out 25g PEG and dissolve in 50mL MilliQ H2O
- In a sterile field, filter sterilize 50% PEG 3350 into a sterile 50mL falcon tube
- Label and store in the appropriate location within the chemical cabinet
1M Lithium Acetate
Materials
- 10.2g Lithium Acetate
- 100mL MilliQ H2O
- Dissolve 10.2g Lithium Acetate in 100 mL MilliQ H2O
- In a sterile field, filter sterilize 1M Lithium Acetate into 2 sterile 50mL falcon tubes
- Label and store in the appropriate location within the chemical cabinet
Breaking Buffer
Courtesy of Stockinger Lab.
Materials
- 100 mM Tris-HCl (pH 8)
- 1 mM Dithiothreitol (DTT)
- 20% Glycerol
- MilliQ H2O
- Combine Tris-HCl, and glycerol in a breaker. Add stir bar and turn stir plate on
- Add to graduated cylinder and top off to final volume with MilliQ H2O
- Pour into stock bottle, invert to mix
- Before use, aliquot out required amount and add in DTT.
- DTT degrades rapidly and thus should be added immediately before using a breaking buffer
- Stebbins, J. Assay of β-Galactosidase in Yeast. Stockinger Lab. https://stockingerlab.osu.edu/sites/stockinger/files/imce/PDFs/Protocols/BetaGalAssays.pdf
Z Buffer
Courtesy of Stockinger Lab.
Materials
- 1.61g Na2HPO4 • 7H2O
- 0.55g NaH2PO2 • H2O
- 0.075g KCl
- 0.0246 MgSO4• 7H2O
- MilliQ H2O to final volume of 100 mL
- Add 50 mL of MilliQ H2O to a beaker with a stir bar and turn on stir function
- Weigh out reagents on a fine balance scale. Rinse out weigh boats after each use with 2 mL MilliQ H2O and add to beaker to get any particulate matter left over. Mix till dissolved
- Using a pH strip or pH meter to confirm pH is 7
- Add to graduated cylinder and top off with MilliQ H2O to 100 mL. Pour into stock bottle
- Store at 4 °C and add DTT to 10 mM before each use.
- DTT degrades rapidly and thus should be added immediately before using Z buffer
- Stebbins, J. Assay of β-Galactosidase in Yeast. Stockinger Lab. https://stockingerlab.osu.edu/sites/stockinger/files/imce/PDFs/Protocols/BetaGalAssays.pdf
2-Nitrophenyl-beta-D-galactopyranoside Stock Solution
Courtesy of Stockinger Lab.
Materials
- 2-Nitrophenyl-beta-D-galactopyranoside, 99% (ONPG)
- Z buffer
- Add 4mg ONPG per 1 mL Z buffer
- Dissolve with a stir bar. Cover while dissolving to protect, as ONPG is photosensitive
- Store at -20 °C
- Stebbins, J. Assay of β-Galactosidase in Yeast. Stockinger Lab. https://stockingerlab.osu.edu/sites/stockinger/files/imce/PDFs/Protocols/BetaGalAssays.pdf
Sodium Carbonate Stock Solution
Courtesy of Stockinger Lab.
Materials
- 26.5g Na2CO3 (Sodium Carbonate) • 7H2O
- 250 mL MilliQ H2O
- Add 100 mL MilliQ H2O to a beaker with a stir bar. Turn on stir function
- Add Na2CO3 and dissolve with a stir bar
- Pour into a graduated cylinder and top off volume to 250 mL
- Store in stock bottle at 4°C
- Stebbins, J. Assay of β-Galactosidase in Yeast. Stockinger Lab. https://stockingerlab.osu.edu/sites/stockinger/files/imce/PDFs/Protocols/BetaGalAssays.pdf
1M Dithiothreitol Stock Solution
Materials
- 1.54mg (Dithiothreitol) DTT
- 1 mL MilliQ H2O
- Read DTT SDS
- Add 1.54mg DTT to a microfuge tube with 1 mL MilliQ H2O. Vortex on high to dissolve
- Store at -20 °C
100 mM Phenylmethylsulphonyl fluoride stock solution
CAUTION: PMSF is ANTI-PROTEASE, is a strong hydrogen-fluoride (HF) RELEASER, is highly CORROSIVE, and is ACUTELY TOXIC. Work in fume hood with appropriate PPE. Whenever possible, use a less toxic alternative.
Materials
- 174.2mg Phenylmethylsulphonyl Fluoride (PMSF)
- 1 mL anhydrous isopropanol
- Read PMSF SDS
- Add 174.2mg PMSF to a microfuge tube with 1 mL anhydrous isopropanol. Vortex on high to dissolve
- Store at -20°C in flammables section
B-Galactosidase assay
Courtesy of Stockinger Lab.
Materials
- SC-URA Liquid Media
- SC-URA Agar Plates
- 42°C Water Bath
- Glass culture tubes
- Breaking buffer with DTT added
- 100 mM PMSF
- Z buffer
- 1M DTT
- ONPG Stock Solution
- Na2CO3 Stock Solution
- Sterile water
- Inoculation loop
- Glass or disposable spreader
- 0.5 mm Sterile Glass Beads
- Day 1
- Inoculate 5 mL SC-URA (YPD for wild-type yeast) with transformed S. cerevisiae in a sterile 16 mm test tube
- Incubate overnight at 30°C, shaking at 180 rpm
- Day 2
- Prewarm SC-URA (YPD for wild-type yeast) to 30°C. Fill a new set of sterile 16 mm test tubes with 10 mL of applicable media
- Take OD600 of 5mL cultures. Calculate how much to inoculate 10 mL fresh media with to reach an OD600 of 1.0 at the time of cell harvest on day 3 using the steps below:
- Determine the doubling time of yeast strain in media of choice. Stockinger lab reports a time of 140 minutes in minimal media.
- Determine how many “doubles” yeast will have undergone at time of cell harvest on day 3. Ex. Harvesting 20 hours later = 8.57 doubles, round down to 8.
- 2⁸ = 256. Divide OD600 final by 2 to the power of # doublings = 1.0 / 256 = 0.0039
- Use C₁V₁ = C₂V₂ to calculate starting concentration (Overnight culture OD600(V₁) = (10)(0.0039))
- Inoculate 10mL media with the correct amount of 5mL overnight culture, incubate overnight at 30 °C, shaking at 180 rpm
- Day 3
- Remove overnight culture from incubation and transfer 5mL of culture to a 15mL disposable falcon tube. Place tubes onto ice
- Spin down the 5mL at 2000xg for 5 minutes and decant supernatant
- Resuspend cells in 1mL of sterile water and transfer to a 1.5 microfuge tube, and spin down at 3000xg for 2 minutes. Decant supernatant
- Resuspend cells in 250 uL of breaking buffer. Prior to use, add DTT. Cells can now be frozen at -20°C and assayed later
- If cells were frozen, thaw them on ice. Add glass beads until the beads reach a level just below the meniscus of the liquid. Add 12.5 uL of PMSF stock solution
- Vortex 6 times at top speed in 15-second bursts. Chill on ice between bursts
- Add 250 uL of breaking buffer and mix well. Withdraw the liquid extract after plunging the tip of a P1000 into the bottom of the tube
- Clarify the extract by centrifuging 2000xg. For a chilled centrifuge, spin for 15 minutes. For a room temperature centrifuge, spin at 5-minute increments and chill at -20 °C for 10 minutes between bursts to preserve β-Galactosidase protein. Transfer the clarified supernatant to a new microfuge tube. Extract can be stored at -20 °C
- In a disposable culture tube add 0.9 mL of Z-buffer (add DTT to Z-buffer prior to use). Add 100uL of extract to Z buffer and pipette up and down to mix
- Initiate the reaction by adding 200uL of ONPG stock solution and note what time the addition is made. Incubate at 28 °C until a pale-yellow color appears
- Note: To ensure that color change is not due to ONPG auto-hydrolysis, run a negative control containing 0.9 mL of Z-buffer with DTT and 200uL of ONPG stock solution
- Terminate the reaction by adding 500uL of Na2CO3 stock solution. Measure the absorbance at 420 nm
- Store in stock bottle at 4°C
- Stebbins, J. Assay of β-Galactosidase in Yeast. Stockinger Lab. https://stockingerlab.osu.edu/sites/stockinger/files/imce/PDFs/Protocols/BetaGalAssays.pdf
GFP Fluorescence Analysis
Courtesy of Stockinger Lab.
Materials
- Black, untreated, flat bottom 96 well plates
- SC-URA liquid media, YPD liquid media
- Overnight cultures of wild-type yeast and transformed yeast
- 0.05M Lead Nitrate
- MiBS Plate Reader
- Sterile water
- Multichannel pipettor, P10 pipettor, assorted tips
- Appropriate PPE
- Read Lead Nitrate SDS
- Using a multichannel pipette, set up 96-well plate corresponding to table below. Repeat (1-4) for each technical replicate, or concentration gradient group being tested
Pb7S Test Lane PB14S Test Lane Wild-Type Control Lane Wild-Type Control Lane A 100 µL SC-URA 100 µL SC-URA 100 µL YPD 100 µL YPD B 100 µL SC-URA 100 µL SC-URA 100 µL YPD 100 µL YPD C 100 µL SC-URA 100 µL SC-URA 100 µL YPD 100 µL YPD D 100 µL SC-URA 100 µL SC-URA 100 µL YPD 100 µL YPD E 200 µL SC-URA 200 µL SC-URA 200 µL YPD 100 µL YPD - Determine volume of Lead Nitrate required for maximum concentration being tested. Use C1V1 = C2V2 to calculate. Any work with Lead Nitrate must use appropriate PPE
Example calculation: for a 0.2 ug/ uL concentration from 0.05M stock- (10.36 g/L) (V1) = (200 ug)(1 mL)
- V = 0.0193
- Depending on your volume, dilute in sterile water by an appropriate factor to ensure accurate pipetting
- Add maximum concentration lead nitrate being tested to E1, E2, and E3. Do not add to E4. Mix up and down 5-10 times slowly with pipette to ensure media and lead are thoroughly mixed
- Using multi-channel pipette, take 100 uL from E1, E2, E3 and add into D1, D2, D3. Mix up and down 5-10 times slowly with pipette to ensure media and lead are thoroughly mixed
- Repeat this serial dilution until all wells (in columns 1-3) have had lead nitrate added. After row A has been mixed, take up 100uL of volume using multi-channel pipette and discard in appropriate liquid waste
- Take OD600 of yeast overnight cultures. Normalize all to an OD600 of 0.4 by diluting with sterile water
- Add 100 uL of yeast overnight culture to applicable well, including lane 4. See table under (2) above for which overnight culture to inoculate with. Mix up and down 5-10 times with pipette. Avoid bubbles. Change tips in between
- Read on MiBS plate reader at the correct wavelength to excite GFP. Take measurements every half hour to track fluorescence
- Carefully dispose of any waste or equipment that came into contact with lead nitrate
Plasmid Design Overview
Plasmid Design
Creation and Conformation of Reusable Entry Vectors
- Golden Gate Assembly (GGA) of pYTK002 OR pYTK003 OR pYTK004, pYTK047, pYTK067 OR pYTK068 OR pYTK072, pYTK074, pYTK084, pYTK081. Exclude heat inactivation step and end cycle on ligation as per iGEM Guelph 2025 protocols
- Transformation of GGA products into competent DH5α E. coli cells. Incubation for 24-48 hours until colonies appear
- Green/white/red colony screening of transformant E. coli. If no white colonies appear, return to (1)
- Green = Entry Vector or GFP Dropout (pYTK047) in original backbone. Proceed to (4)
- White = pYTK part in original backbone. Return to (1)
- RFP in KanRColE1 original backbone (pYTK084 undigested part). Return to (1)
- Overnight culture green transformants
- Miniprep of overnight cultures
- Digest of miniprep with a single cutter restriction enzyme, followed by gel electrophoresis. If bands match expected size, proceed to (7). If bands are an incorrect size, return to (1)
- Create glycerol stocks of selected positive transformant E. coli colonies for long term storage at -80°C
Creation and Conformation of Plasmid Constructs for Integrase and Riboswitch Testing
- Golden Gate Assembly (GGA) of pre-assembled entry vector construct and corresponding parts to TU1, TU2 and TU3
- Transformation of GGA products into competent DH5α E. coli cells. Incubation for 24-48 hours until colonies appear
- Green/white colony screening of transformant E. coli. If no white colonies appear, return to (1)
- Green = Entry Vector
- White = Transcriptional Unit
-
Option A)
- Use colony PCR of white transformants using appropriate primer set(s) - the selection of 3-5 colonies is ideal
- Run gel electrophoresis. If amplicons match the expected size, proceed to (4A, iii). If amplicons are an incorrect size, return to (1), or inspect primers
- Overnight culture white transformants
- Miniprep of overnight cultures
-
Option B)
- Overnight culture white transformants
- Miniprep of overnight cultures
- Digest of TU1, TU2, and TU3 with a single cutter restriction enzyme, followed by gel electrophoresis. If bands match expected size, proceed to (6). If bands are an incorrect size, return to (1)
- Miniprep of overnight cultures
- Create glycerol stocks of selected positive transformant E.coli colonies for long term storage at -80°C
Riboswitch Testing Overview
Riboswitch Testing
Objective
Validate that Pb7S and Pb14S can bind to Pb with high affinity and undergo a conformational change strong enough to pause PIC for initiation of ATG deficient target gene. GFP used as a fluorescent reporter. Compare the efficiency of Pb7S and Pb14S to select the better aptamer and determine the minimum of lead needed to initiate translation, as well as the maximum concentration of lead in which this unit is still fully functional.
Plasmid Constructs Required
Transcriptional Unit (TU) | Purpose | Parts Required |
---|---|---|
TU1 - Pb7S Function | Tests the function of Pb7S aptamer using GFP as a reporter. |
(1) pTEF2 (2) Pb7S Aptamer (3) GFP (-ATG) |
TU2 - Pb14S Function | Tests the function of Pb14S aptamer using GFP as a reporter. |
(1) pTEF2 (2) Pb14S Aptamer (3) GFP (-ATG) |
TU3 - Positive Control | Determines 100% GFP fluorescence at GFP excitation wavelength to determine relative expression of GFP in TU1 and TU2. |
(1) pTEF2 (2) Type 2 Spacer (3) Super-fold GFP |
No Vector | Determines if yeast have background fluorescence at GFP excitation wavelength for more accurate readings of TU1 and TU2. | BY4741 Wild-Type Yeast |
All protocols listed in the steps below are found under iGEM Guelph 2025 protocols.
See Plasmid Design: Creation and Confirmation of Plasmid Constructs for Integrase and Riboswitch Testing for instructions on assembly of required transcriptional units.
Validation of Aptamer
- Transformation of sequenced transcriptional units into BY4741 yeast onto SC-URA media. Incubation for 3-7 days until colonies appear
- Restreak of transformant colonies onto fresh SC-URA for further selection
- Conduct 96-Well Plate assay
- Graph MiBS plate readings and calculate standard deviation
Integrase Testing Overview
Integrase Testing
Objective
Validate the ΦBT1 integrase can invert genetic elements flanked by
attB and attP recognition sites. Three transcriptional units,
consisting of a positive control, negative control, and test unit, alongside
wild-type yeast are used. LacZ replaces the SSP to conduct a
colorimetric assay using ONPG. β-Galactosidase cleaves ONPG to form a yellow
substrate. Reverse LacZ with attB and attP sites is placed
downstream of integrase. If integrase successfully inverts this construct,
forward LacZ is formed, placing the ATG start codon in frame of a strong
promoter, causing the production of β-Galactosidase, indicated by a yellow
color change.
Plasmid Constructs Required
Transcriptional Unit (TU) | Purpose | Parts Required |
---|---|---|
TU1 - ΦBT1 Function | Determine if ΦBT1 is being produced and successfully facilitates the inversion of the select DNA sequences flanked by attP/attB sites. |
(1) pTEF2 (2) ΦBT1 Integrase (3) attP - Reverse lacZ - attB |
TU2 - Negative Control | Ensures that the results observed from TU1 are due to ΦBT1 activity and not transcriptional read-through. |
(1) pTEF2 (2) Type 3 Spacer (3) attP - Reverse lacZ - attB |
TU3 - Positive Control | Ensures that the results observed are due to a functional lacZ gene. |
(1) pTEF2 (2/3) attP - lacZ - attB |
No Vector | Ensures that the negative control does not have statistically different expression of lacZ compared to wild-type yeast. | BY4741 (no vector) |
See Plasmid Design: Creation and Confirmation of Plasmid Constructs for Integrase and Riboswitch Testing for instructions on assembly of required transcriptional units.
Validation of Memory System
- Transformation of sequenced transcriptional units into BY4741 yeast onto SC-URA media. Incubation for 3-7 days until colonies appear
- Restreak of transformant colonies onto fresh SC-URA for further selection
- Conduct ONPG assay. Use the table below to assess results:
Transcriptional Unit Expected Color TU1 - Integrase Test Yellow, ONPG cleaved TU2 - Negative Control Clear, no ONPG cleaved TU3 - Positive Control Yellow, ONPG cleaved BY4741 - Wild-Type Clear, no ONPG cleaved - Run an ANOVA and Tukey post-hoc to determine if results are significant
- Repeat ONPG assay culturing yeast over a time course to determine if there is an increase in the ration of forward LacZ to reverse LacZ in integrase test yeast