What indicates a positive DNase result after adding 0.1 N HCl to the plate?

What indicates a positive DNase result after adding 0.1 N HCl to the plate?

• A. Gels on refrigeration
• B. Green slant
• C. Agar becomes cloudy
• D. Agar clears around the colony

Answer: (D)

A positive DNase result is indicated by the observation of agar clearing around the colonies after adding 0.1 N HCl to the plate. DNase is an enzyme that degrades DNA, and the presence of this enzyme can be detected through its action on DNA in the medium. When DNase breaks down the DNA, it leads to the formation of soluble components. Upon adding HCl, which precipitates DNA, any DNA that remains will cloud the medium, whereas the areas where DNase has degraded the DNA will remain clear because the produced components do not precipitate. Thus, clear zones around colonies confirm that the organism produces DNase. This clarity indicates the enzymatic action and is a direct positive result for DNase production, helping differentiate species based on their ability to utilize DNA as a nutrient source.

A positive DNase result is indicated by the observation of agar clearing around the colonies after adding 0.1 N HCl to the plate. DNase is an enzyme that degrades DNA, and the presence of this enzyme can be detected through its action on DNA in the medium. When DNase breaks down the DNA, it leads to the formation of soluble components.

Upon adding HCl, which precipitates DNA, any DNA that remains will cloud the medium, whereas the areas where DNase has degraded the DNA will remain clear because the produced components do not precipitate. Thus, clear zones around colonies confirm that the organism produces DNase. This clarity indicates the enzymatic action and is a direct positive result for DNase production, helping differentiate species based on their ability to utilize DNA as a nutrient source.