Crystal violet stain is too dark — high background (Colony Formation Assay)

Question

Accepted Answer

Entire dish is deeply purple; individual colony boundaries are blurred by background staining. Common causes: 1) Staining time was too long 2) Crystal violet concentration was too high 3) Insufficient washing left residual dye Solutions: 1) Reduce staining time (15 – 20 min) 2) Lower crystal violet concentration (0.05 – 0.1 %) 3) Increase wash count (3 – 5 gentle rinses in water)