Plate scratches or impurities interfere with imaging (Colony Formation Assay)

Question

Accepted Answer

Imaging shows linear scratches, dust specks, or crystal violet precipitate that look like colonies or obscure them. Common causes: 1) Dish quality is poor (scratched or aged plastic) 2) Crystal violet has precipitated in the bottle 3) Photographing under uneven lighting creates reflections Solutions: 1) Use fresh, high-quality tissue culture dishes 2) Filter (0.22 µm) and re-dissolve crystal violet stock before use 3) Photograph under even diffuse lighting; avoid direct flash that produces reflections