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. 2007 Winter;6(4):307–315. doi: 10.1187/cbe.06-12-0204

Figure 2.

Figure 2.

Close-up of the 200 μl concentration of the student's experimental results to demonstrate the differences between the red, pink, and white colonies. (A) Negative control plates. Cells were treated with increasing concentrations of water (1–100 μl, 2–200 μl, 3–300 μl, and 4–400 μl) and spread on the plates as indicated. (B) Positive control plates. Cells were treated with increasing concentrations of ethyl methane sulfonate (1–0.5%, 2–1%, 3–1.5%, and 4–2%) and spread on the indicated plate. (C) Experimental. Cells were treated with increasing concentrations of methylene blue dye obtained from a children's microscope kit (Microscope Lab Max by Discovery Planet, Bowen Hill Ltd., Hong Kong) (1–100 μl, 2–200 μl, 3–300 μl, and 4–400 μl) and spread on the plates as indicated. −ISO is synthetic media lacking isoleucine and −TRP is synthetic media lacking tryptophan.