DNASE TEST

Objective:

DNase mediates the hydrolysis of DNA. Methyl Green indicator is stable at pHs above 7.5 but becomes colorless at lower pHs. The hydrolysis of DNA in the agar by bacterial DNase reduces the agar pH.

Test Procedure

1. Using a sterile loop, inoculate a DNA+Methyl Green agar plate with the fresh bacterial culture. Use a heavy streak line for each bacterial strain to be tested. Be sure to label the plate bottom properly for each strain.
2. Incubate at 37°C for 48 hrs.

Interpretation

The test is positive if clearing develops around the areas of growth. If the color of the agar around the growth is unchanged, the test is negative (i.e., the organism is not able to produce DNase).