Catalase Test


What is the purpose of the test? 


The purpose is to see if the microbe has catalase, a protective enzyme capable of destroying the dangerous chemical hydrogen peroxide.



How is catalase activity determined? 


Growth from an overnight culture of the microbe is smeared on a microscope slide. A drop of 3% hydrogen peroxide is added. If copious bubbles are observed, the microbe is positive for catalase.



What medium is used?  


The medium for growth can be most any general purpose medium. Care should be taken to avoid using blood agar, as blood cells contain catalase and trace contamination of medium can lead to false positive results. Removal of cells from an isolated colony on a streak plate is recommended.



How is the test performed?  


An inoculum from a pure culture is streaked on a sterile plate of general purpose growth medium The inoculated plate is incubated at 35-37 C for 24 hours. Growth from the plate is smeared on a microscope slide and a drop of hydrogen peroxide is placed on the smear. Copious bubbles liberated in the hydrogen peroxide by the growth indicates presence of catalase.



What reagents are added?


Hydrogen peroxide is added to the smear on the surface of the microscope slide.



In VirtualUnknownTM Microbiology a video is provided that depicts removal of cells from an isolated colony of the unknown microbe and placement on a microscope slide for performing the test.  Catalase is then added and the reaction is observed.  To view the catalase test in VirtualUnknown™ Microbiology, complete the following steps:


1. Select View -> Catalase Video from the Main Menu.


2. Press the Play button to watch the video. A short video clip showing microscopic observation of a catalase test for the unknown organism will play.


3. Observe the results. If the bacterium possesses catalase, copious bubbles will be liberated upon the addition of the hydrogen peroxide. If the bacterium lacks catalase, there will be no perceptible change in the appearance of the smear on the microscope slide.


4. Record the result by pressing the Record Result button on the catalase video screen and selecting the appropriate result.