Catalase test

Catalase test

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  Catalase test
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  Background • Enzyme namecatalase important enzyme in protecting the cell from oxidative damage by reactive oxygen species (ROS). • Substrate name hydrogen peroxide • Enzyme action breakdown of toxic H2O2 producing oxygen gas and water catalase • 2H2O2 2H2O + O2 • 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
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  Background • When hydrogenperoxide 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
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  PROCEDURE a. Place asmall 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 H2O2 onto the smear. If needed, mix with a toothpick. DO NOT use a metal loop or needle with H2O2; it will give a false positive and degrade the metal.
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  Interpretation c. +ve resultrapid evolution of O2 as evidenced by bubbling. d. –ve result no bubbles or only a few scattered bubbles.
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  To Know • Catalaseis usually located in a cellular, bipolar environment organelle called the peroxisome • Louis Jacques Thénard, who discovered H2O2 (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