Paris/PROTOCOLS

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Prepare to begin

This topic is adressed to all our informatics-physics-I'm-afraid-of-the-bench fellows. So, if you finally found the courage to dare the pipettes, PCRs and nicely smelling bacteria, welcome!


Pipettes dispense various volumes. The plunger button indicates the maximum volume (microliters) that the pipette is designed to handle. For example, P-20 will handle up to 20 microliters.
The digital volume indicator is read from top to bottom. For P-2, P-10, P-20, P-100, and P-200, black digits indicate microliters and red digits tenths and hundredths of microliters. For P-1000, red digits indicate milliliters and black digits microliters.

What to do when you have it in you hand?

-Hold the pipette in one hand (it doesn't bite...). With the other hand, turn the volume adjustment knob counterclockwise so the volume indicator is 1/3 revolution above the desired setting, then slowly turn clockwise until the indicator shows the desired volume.
-Attach a new disposable tip to the pipette shaft.
-Press the plunger to the FIRST stop. This part of the stroke is the volume displayed by the indicator.
-Holding the pipette vertically, immerse the tip a few millimeters into the sample.
-Allow the pushbutton to return slowly to the UP position. Avoid to blurt out the plunger button abruptly : there are bulls appearing and your volume is false...
-Ensure that the full volume of sample was properly drawn into the tip.
-Withdraw the tip from the sample.
-To dispense the liquid, gently touch the tip to the side of the receiving vessel, immersing the tip into liquid within the vessel. Press the plunger to the SECOND stop.
-With the plunger fully pressed, withdraw the tip carefully, wiping residual drops against the vessel wall.
-Allow plunger to return to the UP position.
-Discard the tip by depressing the tip ejector button.

Note down that different tips exist : ensure that you have the right one (labels will indicate you the size, etc.). It's better to use filter tips.
To train, you can simply pipette water : it's important to know how much 1 µl is...

To be continued...


  • Growing bacteria in liquid medium


-Light the Bunsen burner. It permits you to keep a 10 cm perimeter sterile et thus not to contaminate your future colonies.
-Get a 50mL Falcon tube and put into 5 mL of LB medium. Add supplementary stuff if needed (antibiotics, metabolites, etc.).
-Pick up a sterile toothpick. Use it to gather a single colony of cells (you know, a white point on your Petri dish...).
-Place the toothpick with the colony into the solution.
-Incubate overnight at 37°C with shaking (at about 200 rpm).

Next morning, after a cup of coffee and a croissant, you can check up (see image 1).