Matti Koivisto, an undergraduate student working in the laboratory of Kari Haajanen at Turku University of Applied Sciences, designs solutions similar to this one to detect the bacteria Escherichia coli. He uses a dye called rhodamine 6G, which has a strong orange color when dissolved in ethanol. In solution, the dye separates into negatively and positively charged ions, the latter of which are largely responsible for the dye’s color. Negatively charged molecules on the outer membranes of E. coli attract the dye’s positive ions. This interaction causes the dye to change color to a pinkish hue, and the level of color change allows Koivisto to gauge how many of the bacteria are present.
Submitted by Matti Koivisto
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