Details - Public Health Image Library(PHIL)

ID#:

16225

Caption:

This Petri dish culture plate contained a growth medium that had been colored blue due to the addition of toluidine blue dye. The medium was subsequently inoculated with an Enterobacter sakazakii bacterial culture at 1-day intervals, being allowed to incubate for a 1-day (bottom), 2-day (middle), and a 3-day (top) time period, at a temperature of 36^°C. The resultant DNase reaction revealed positive results after a 2, and 3-day incubation period, evidenced by the light-pink halo surrounding the punctate-, hyphenated-, and X-shaped colonies. The DNase test measures the production of the extracellular enzyme, deoxyribonuclease (DNase), a chemical break down DNA. In a positive DNase test, the DNA is fragmented, freeing the double-stranded DNA (dsDNA) from its bonds with the dye contained in the medium, in this case toluidine, and leaving behind a lightly colored, pinkish tinted halo around the colonies.

High Resolution:

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Content Provider(s):

CDC/ Dr. J.J. Farmer

Creation Date:

1978

Photo Credit:

Links:

Categories:

CDC Organization