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August

August 5th

The goal is to select a bacteria able to develop on 2-nonenal. We made 2 new media:

1) M9 Minimal Media 100% Glucose

• 200mL M9 Salts
• 0.1mL CaCl2 1M
• 2mL MgSO4 1M
• 20mL Glucose 20%
• Water: bring to 1L

2) M9 Minimal Media 50% Glucose - 50% 2-Nonenal (according to the number of carbon atoms)

• 200mL M9 Salts
• 0.1mL CaCl2 1M
• 2mL MgSO4 1M
• 10mL Glucose 20%
• 10mL 2-nonenal 10,7%*
• Water: bring to 1L

3) M9 Minimal Media 100% 2-nonenal

• 200mL M9 Salts
• 0.1mL CaCl2 1M
• 2mL MgSO4 1M
• 20mL 2-nonenal 10,7%*
• Water: bring to 1L

We autoclaved 6 bottles (2 of 500mL for each)

Then, we made liquid culture of C.striatum in media 1) to try if the minima media works.

* Concentration of the 2-nonenal solution: In M9 Media, we use 20mL of Glucose 20% (200g/L). The concentration of glucose is C=200/M=1.09 mol/L. Glucose has 6 carbons while 2-nonenal has 9, so we need 2/3 of the glucose volume to have the same amount of carbon atoms. C=2/3*1.09=0.74 mol/L and then 0.74*M=103.7g/L. That's why the concentration of the 2-nonenal solution is 10.73%. We also added Tween80.

August 6th

We poured 20 plates of each of the 3 media with 350mL of an agar solution and 100mL of medium.

Then we used 3 plates of each type to culture skin bacteria from 3 spots: arm, armpit and forehead. Ursczula sampled bacteria from her skin with a loop and for each spot she diluted the bacteria in 300uL of NF Water. Then we plated 100uL of each solution in each of the 3 types of plates and incubated them at 37°C.

	M9 100% glucose	M9 50%-50%	M9 100% 2-nonenal
Arm	x	x	x
Armpit	x	x	x
Forehead	x	x	x
NEB (control)	x	x	x

August 8th

After 2 days, nothind has developped on the M9 plates. M9 media is actually really slow for the development of any strain. That is why we created a new media which would be like the real skin environment: synthetic sweat according to this recipe

According to the recipe, fatty acids seem to be the main source of carbon in synthetic sweat so we replaced them by 2-nonenal.
We made 2 media:
1) without fatty acids
2) without fatty acids and with 2-nonenal mixed with 10% of Tween 80.

August 11th

Results of M9 plates

	M9 100% glucose	M9 50%-50%	M9 100% 2-nonenal
Arm	Many very small colonies	6	0
Armpit	Many very small colonies	0	0
Forehead	27	5	0
NEB (control)	Many	many	0

Analysis:
The fitness of bacteria is better on 100% Glucose than on 50-50%. No colony develops on 2-nonenal, not even NEB. Then we can suggest that 2-nonenal is not used as a carbon source and that the difference of fitness between 100% glucose and 50-50% is only due to the lower amount of glucose in 50-50%. We should have made plates with only 50% of glucose to compare.

We also plated samples on synthetic sweat:

	NEB	Forehead	Nose
1) Without fatty acids	x	x	x
2) Without fatty acids and with 2-nonenal	x	x	x

On August 10th, Jake tried a new medium with peptone added to M9. He made 2 media (20 plates of each):

• iGEM medium 1 (100% glucose)
• pancreatic digest of casein: 15 g
• glucose: 5 g
• NaCl: l5 g
• Agar: 15 g
• Water: 1 L
• iGEM medium 2 (100% 2-nonenal):
• pancreatic digest of casein: 15 g
• 2-nonenal: 10 g
• Tween 80: 250uL (premix with 2-nonenal before adding to the medium)
• NaCl: l5 g
• Agar: 15 g
• Water: 1 L

I prepared 2 new media:

• iGEM medium 3 (50% glucose)
• pancreatic digest of casein: 7.5 g
• glucose: 1.25 g
• NaCl: 7.5 g
• Agar: 7.5 g
• Water: 0.5 L
• iGEM medium 4 (50% glucose - 50% 2-nonenal):
• pancreatic digest of casein: 7.5 g
• glucose: 1.25 g
• 2-nonenal: 2.5 g
• Tween 80: 125uL (premix with 2-nonenal before adding to the autoclaved medium)
• NaCl: 7.5 g
• Agar: 7.5 g
• Water: 0.5 L

I autoclaved them at 111°C - 3min (programm 5).

Then, I added the 2-nonenal to iGEM medium 4: density of nonenal is 0.846g/mL so I put 2.5/0.846 = 2.96 mL of 2-nonenal mixed with 125uL of Tween 80. I poured 20 plates of each medium and then plated:

September

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October

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