From 2011.igem.org

Cytometry Protocol

Colonies from plates:

1. Stab cells from isolated colony on plate and suspend them in 50 uL PBS buffer.
2. Dilute PBS culture by adding 1 uL to 100 uL fresh PBS buffer.
3. Measure fluorescence levels on cytometer.

Cells from liquid culture:

1. Grow cells to mid-exponential phase (generally, OD 0.1 to 0.2).
2. Dilute cells 1:20 in PBS buffer supplemented with chloramphenicol or kanamycin (choose an antibiotic the cells aren't resistant to), and store on ice.
3. Measure fluorescence levels on cytometer.