Crystal violet staining and quantification

Log phase cells (0.5×10⁶/ml) were plated into 12-well plates and incubated for 72 hr. After removing media, cells were stained with Crystal Violet staining solution (0.05% w/v Crystal Violet, 1% formaldehyde, and 1% methanol in 1xPBS) for 20 min at room temperature. After removing the staining solution, plates were gently washed by dipping into water several times and were air dried overnight. For quantification, 1ml of 10% of acetic acid was added into each well and incubated for 20 min on shaker. 100μl of each sample was transferred to 96-well plate and optical density was measured at a wavelength of 590nm.