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From 2014.igem.org

Contents 1 Amplification of Phage using Helper Phage 2 Bacterial Transformation Using Frozen Competent Cells 3 Bacterial Conjugation 4 Making Chemically Competent Bacteria

Amplification of Phage using Helper Phage

• here is the protocol

1. transformation

Need

• Plate of infectable cells that contain F’ episome
• 2.5M NaCl/20% PEG-8000
• 1x TBS

Day 1

1. Add a fresh colony of infectable cells to 50mL LB in 125mL flask.
   1. Include phagemid antibiotic only.
   2. Grow at 37°C, 250rpm until OD is between 0.03 and 0.05
2. Add the helper phage to a final concentration of 1 x10^8 phage/mL
3. Incubate for 60-90 minutes, shaking
4. Add Helper Phagemid antibiotic to a high concentration
5. Grow for 14-18 hours at 37°C, shaking

Day 2

1. Spin culture at 4,000 x g for 10 minutes
2. Transfer supernatant to a fresh conical. Repeat spin on supernatant
3. Transfer the upper 90% of supernatant to a new conical
4. Add 0.2 volume of 2.5M NaCl/20% PEG-8000 to the new conical. Gently mix
5. Incubate at 4°C for at least 60 minutes
6. Centrifuge at 12,000 x g for 10 minutes. Carefully decant
7. Spin again briefly
8. Gently resuspend pellet in 1.6mL 1x TBS
9. Aliquot 800ul into 2 microfuge tubes. Proceed with both tubes
10. Spin sample for 1 minute to pellet remaining cells. Transfer supernatant to fresh tubes
11. Add 160ul of 2.5M NaCl/20% PEG-8000 solution to each
12. Let sit at room temperature for 5 minutes
13. Spin at 1300 x g for 10 minutes
14. Decant the supernatant
15. Spin briefly. Remove supernatant with pipet
16. Resuspend pellet in 200ul 1x TBS.
    1. If desired, combine contents of both tubes into one

2.5M NaCl/20% PEG-8000 (5x)

• PEG-8000 100 g
• NaCl 75 g
• H2O 400 mL
• Bring final volume to 500 mL

TBS (1x)

• Tris 6.05 g
• NaCl 8.76 g
• H2O 800 mL
• Adjust pH to 7.6 with 1M HCl
• Adjust volume to 1 L

Bacterial Transformation Using Frozen Competent Cells

Before you start

• Heat hot plate or water bath to 42°C
• Warm selection plates to 37°C

Transformation

1. Thaw chemically competent cells on ice for 10-15 minutes
2. Add 40ul cells to fresh 1.7mL tube
3. Add DNA
   1. If using a ligation product add up to 10ul of sample
   2. If using supercoiled plasmid add 100ng
4. Incubate on ice for 30 minutes
5. Heat shock cells on hot plate (or water bath) for 30-45s* @ 42°C
6. Incubate on ice for 2-5 minutes
7. Add 200 μL SOC and shake gently for 1-2 hours @ 37° C
   1. (Note: Can also recover in 960ul. After recovery, gently spin cells and remove supernatant. Resuspend in 200ul LB)
8. Plate 100-200ul cells onto selection plates
   1. If high efficiency is expected, we suggest also plating a 1:10 dilution
9. Once dry, turn upside down (agar on top) and incubate overnight @ 37° C

Optimal timing depends on cells

SOC (1L)

• Tryptone 20 g
• Yeast Extract 5 g
• MgSO4 4.8 g
• Dextrose 3.6 g
• NaCl 0.5 g
• KCl 0.186 g

Bacterial Conjugation

Need

• Donor cells: Cells already containing F’ episome
• Recipient cells: Cells with a resistance marker that is absent from donor cells
• Double selection plate containing antibiotic to select for F’ episome and a second antibiotic to select for the recipient cells

Day 1

1. Set up liquid overnight of donor cells. Include antibiotic
2. Set up liquid overnight of recipient cells. Include antibiotic

Day 2

1. Mix 500ul of each overnight sample in a new tube. Mix by pipetting or flicking
2. Incubate for 30 minutes at 37°C, shaking
3. Plate 100ul onto double selection plate
   1. We advise also plating a 1:10 dilution
4. Incubate at 37°C

http://inst.bact.wisc.edu/inst/index.php?module=Book&func=displayarticle&art_id=128

Making Chemically Competent Bacteria

To prepare for Day 2

1. Set centrifuge to 4°C
2. MgCl2 and CaCl2 solutions
3. Thaw DMSO
4. Chill tubes
5. Acquire liquid nitrogen or dry ice

Day 1

1. Grow cells O/N

Day 2

1. Add 0.5mL of the overnight culture to 50mL LB
2. Grow until OD is between 0.2 and 0.4
3. Incubate on ice for 30 minutes
4. Centrifuge for 10 minutes at 2700 x g and 4°C
5. Decant. Dry upside down on a paper towel for 1 minute
6. Completely resuspend in 30mL 0.8M MgCl2, 0.2M CaCl2
   1. Gently vortex
7. Centrifuge for 10 minutes at 2700 x g and 4°C
8. Decant. Dry upside down on a paper towel for 1 minute
9. Fully resuspend in 2mL of 0.1M CaCl2
10. Chill sample on ice. Add 70ul DMSO, keeping the sample tube on ice
11. Swirl to mix
12. Incubate on ice for 15 minutes
13. Add 70ul DMSO, swirl to mix, keeping the sample tube on ice
14. Dispense 200ul into pre-chilled 1.7mL tubes
15. Snap freeze with liquid nitrogen or dry ice
16. Store at -80°C until ready to use