* *Place plates on ice.

Wash two times with ice-cold 1X PBS.

Fix cells with ice-cold methanol (stored at –20^oC) for 10 minutes.

Aspirate methanol from plates, move off ice and add enough 0.5% crystal violet solution (made in 25% methanol and stored at room temperature) to cover bottom of plate.

Incubate at room temperature for 10 minutes.

Pour off crystal violet solution into a beaker (can re-use).

Carefully rinse plates in ddH₂0 until color no longer coming off in rinse.

Allow plates to dry at room temperature (may take overnight).Crystal violet stain: stock=1 g. crystal violet
99ml 20% EtOH
working soluion= 20 ml stock
40 ml 95% EtOH
150 ml distilled water