ID#: 3908
Caption:
This image depicts a laboratory technician, who was performing what is known as a string test, which is one of the tests used to differentiate between Gram-negative, and Gram-positive bacteria. Mixing the bacterial sample with 3% potassium hydroxide (KOH), Gram-negative bacteria will lyse, and release their contents of sticky nuclei acids, which when touched by a wire loop, will cling together forming a stringy filament as the loop is lifted away from the slide. Gram-positive bacteria have a thicker cell wall, protected by a layer of peptidoglycan, thereby, able to resist the lytic action of the KOH reagent, and thus release no sticky nuclei acids, and hence, no string is produced.
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Content Provider(s): CDC
Creation Date: 1971
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