catalase test-...........................................

CATALASE TEST.BIOCHEMICAL REACTION,

1. Catalase test

2. Background Enzyme name catalase important enzyme in protecting the cell from oxidative damage  by  reactive oxygen species  (ROS). Substrate name hydrogen peroxide Enzyme action breakdown of toxic H 2 O 2 producing oxygen gas and water catalase 2H 2 O 2 2H 2 O + O 2 Hydrogen peroxide produce due to the aerobic respiration of the cells and have to be breakdown to prevent it’s toxic action on DNA and cell membrane

3. Background When hydrogen peroxide is added to a colony of catalase-producing bacteria, it is broken down and the oxygen that is produced can be seen as bubbles . By catalase test we can distinguish between: G (+ ve ) cocci : Staphylococcus positive where Streptococcus is catalase negative G (+ ve ) bacilli : Bacillus is catalase positive whereas Clostridium is catalase negative All enterobactrieacae (a gram negative bacilli) are catalse positive Lesteria monocytogenes ( a gram positive bacilli) are catalase positive

4. PROCEDURE Place a small amount of growth from culture onto a clean microscope slide. If using colonies from a blood agar plate, be very careful not to scrape up any of the blood agar— blood cells are catalase positive and any contaminating agar could give a false positive. b. Add a few drops of H 2 O 2 onto the smear. If needed, mix with a toothpick. DO NOT use a metal loop or needle with H 2 O 2 ; it will give a false positive and degrade the metal.

5. Interpretation c. + ve result rapid evolution of O 2 as evidenced by bubbling. d. – ve result no bubbles or only a few scattered bubbles.

6. To Know Catalase is usually located in a cellular, bipolar environment  organelle  called the  peroxisome   Louis Jacques Thénard , who discovered H 2 O 2  ( hydrogen peroxide ) Oscar Loew  was the first to give it the name catalase Human catalase works at an optimum temperature of 45 °C pH between 6.8 and 7.5 one catalase molecule can convert approximately 5 million molecules [2]  of hydrogen peroxide to water and oxygen each second