DNase Test

General Information About DNase Agar

DNase agar is a differential medium that tests the ability of an organism to produce an exoenzyme, called deoxyribonuclease or DNase, that hydrolyzes DNA. 

The Basic Chemistry of DNase Agar

DNase agar contains DNA, nutrients for the bacteria, and methyl green as an indicator.  Methyl green is a cation which binds to the negatively-charged DNA. When the DNA is broken down by deoxyribonuclease, it no longer binds to the methyl green.

Reading the Results

If an organism produces DNase, a clear halo will appear around the areas where it has grown. If an organism cannot produce DNase, there will be no halo.

Application of the DNase Test

The DNase test is useful for differentiating species of Enterobacter from species of Serratia. It can also be used to differentiate Staphylococcus aureus and Staphylococcus epidermidis.