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From 2011.igem.org

Adrien Lhomme-Duchadeuil

First, an estimation of how much antibiotics is necessary for Bacillus subtilis (thank you Axel).
Appropriate concentration in antibiotics

• Chloramphemicol : 5-10 µg/mL
• Spectinomycin : 50-100 µg/mL
• Tetracyclin: 25 µg/mL
• Kanamycin: 5 µg/mL
• Erythromycin: 1 µg/mL + 25 µg/mL lincomycin

Results of electroporation: IT WORKED after three trials!

• Positive control worked
• Negative controls didn't show any colonies except when put in the presence of TetR (qty:12,5 µg/mL or 5µg/mL) which was insufficient => I will re-plate the improbable survivors on plates of different tetracyclin concentrations to test resistance.
• Cm resistant strain have survived in low quantities at both 30 and 5 µg/mL of antibiotics
• It seems that even cuvettes that had an electric arc were able to produce a couple colonies, which means that it doesn't anihilate all the bacteria.

Table of resutls of electroporation using Cao et al. method

tube 1: poration control no DNA (12,5 kV: ARC) CTL +: carpet CTL - with Cm (5 and 30 µg/mL): none CTL - with TetR (5 and 12,5 µg/mL): carpet	tube 2: poration control no DNA (10kV: OK) CTL +: carpet CTL - with Cm: none CTL - with TetR: carpet	tube 3: pHM3::TetR (12,5 kV: OK) TetR(5 and 12,5 µg/mL): carpet	tube 4: pHM3::TetR (10 kV: OK) TetR (12,5 µg/mL): carpet	tube5: pHM3::TetR (12,5 kV: ARC) TetR (5 and 12,5 µg/mL): carpet	tube 6: pHM3::TetR (10 kV: OK) TetR (5 µg/mL): carpet
tube 7: S12::Cm (12,5 kV: ARC) Cm 5 µg/mL: 1 colony Cm 30 µg/mL: 1 colony	tube 8: S12::Cm (10 kV: OK) Cm 30 µg/mL: 4 colonies	tube 9: S12::Cm (12,5 kV: OK) Cm 30 µg/mL: 9 colonies Cm 5 µg/mL: 4 colonies	tube 10: S12::Cm (10 kV: OK) Cm 5 µg/mL: 1 colonie	CTL --: no bacteria no growth

Transformation of B. subtilis via electro-poration based on Cao et al. 2011 article

Reagents and Equipment needed
Mannitol, Sorbitol, Trehalose, LB, glycerol (99,5%)
DNA (50 ng/μL), B. subtilis strain for transformation (no need to be competent)
Cuvette (2mm), Gene Pulser (Bio-rad) set on 200 ohms and 25 μF (≈ 5 ms pulses) and 2 to 2.5 kV
Centrifuge set at 3000g and 10 minutes
Micropipettes: P2, P200, P1000
Pipettes: 25 mL, 10 mL, 5 mL

Day 1: preparation

• Growth medium:
  • LB + 0.5 mol.L^-1 sorbitol → expected final volume: 52 mL for 1 cell culture (including 1 mL for taring the absorbance machine)
    • msorbitol ≈ 4,736 g
• Electro-poration medium:
  • de-ionized water + 0.5 mol.L^-1 sorbitol + 0.5 mol.L^-1 mannitol + 0.5 mol.L^-1 trehalose + 10% glycerol (v/v) → expected final volume ≈ 40 mL for 1 round of poration
    • m_sorbitol = m_mannitol ≈ 3,643 g
    • m_trehalose ≈ 7,566 g
    • V_{99,5 % glycerol} ≈ 4 mL
• Recovery medium:
  • LB + 0.5 mol.L^-1 sorbitol + 0.38 mol.L^-1 mannitol → expected final volume: ≈ 1.1 ml per poly... tube (Approximately 10 tubes ≈ 11 mL total)
    • m_sorbitol ≈ 1,002 g (for 10 tubes)
    • m_mannitol ≈ 0,761 g (for 10 tubes)
• Sterilise the solution: Filtration or autoclave.
• Inoculate a falcon containing 10 ml of LB with your subtilis strain and let it grow overnight (37°C with shaking).

Day 2: electro-poration

1. Monitor the OD600 of your overnight culture.
2. In a 500 ml erlenmeyer: dilute your culture into 50mL of Growth Medium so that the OD 600 is 0.01.
3. Let the culture grow (37°C with shaking) until OD600 is between 0.85 and 1.
4. Cool the cells on ice for 5 minutes.
5. NOTE: KEEP ALL YOUR MATERIAL ON ICE AND ALWAYS MANIPULATE ON ICE FROM NOW ON, KEEP AS STERILE AS POSSIBLE.
6. Distribute evenly the culture into two falcons and centrifuge at 3000g for 10 minutes.
7. Get rid of supernatant, tap the falcon upside down on a piece of paper to get rid of as much solution possible. Detach the pellet.
8. Add 20 mL of ice-cold electro-poration medium to one falcon, suspend the cells and transfer the content to the other falcon. Re-suspend.
9. Centrifuge 3000g for 10 minutes.
10. Remove supernatant, detach pellet, add 10 mL of ice-cold electro-poration medium. Centrifuge.
11. Repeat step 10 with 5 mL, 2.5 mL and finally add 0.625 mL (1/80 of initial volume).
12. During the centrifugation time, prepare the poly... tubes (label them) with recovery medium in them and put the cuvettes on ice: 1 of each at least has to be a control of cells without DNA, then 1 for each transformant you wish to make.
13. Transfer in a cuvette: 60 μL of cells + 1 μL of DNA (50ng/μL; none if control).
14. Pulse the cuvette.
15. Transfer immediately the content into the poly... tube (STERILE CONDITIONS).
16. Repeat 13, 14 and 15 for the number of prepared cuvettes.
17. Incubate the poly... tubes at 37°C for 3 to 6 hours.
18. Prepare plates with antibiotics (none for the control).
19. Note: ≈ 25 ml of LBA per petri dish, make sure the antibiotic is well diluted, labeling should be obvious.
20. Plate max 150 μL of transformed cells per petri dish and let grow overnight.