These quistion related to Oxid
These quistion related to Oxidase Assay for Respiration andCatalase Assay experiment
1.In the clinical (real-world) setting, what is the mainobjective of performing laboratory tests such as the oxidase orcatalase assays?
2.Some very important pathogens are positive for the oxidasetest. Use your text or the Internet to find one such example.
3.A student performing the Experiment 2 of this lab set up apositive control with a knowncatalase-positive bacterium. However, he had no remaining hydrogenperoxide in his lab kit supplies so he used some that he had in hishome medicine cabinet. No bubbles were produced afterthe addition of the hydrogen peroxide even though the organism iscatalase positive. What explanation can you give for this
Answer:
1] The oxidase test is used to identify bacteria that producecytochrome c oxidase, an enzyme of the bacterial electron transportchain. All oxidase positive bacteria are aerobic and can use oxygenas a terminal electron acceptor in respiration. Oxidase negativebacteria can be aerobic too [ they are anaerobic as well asfacultative ]
The oxidase or catalase assays help to differentiate thoseaerobic bacteria which produce cytochrome c oxidase from thosewhich do not. So, the main purpose of the test is to categorizebacteria on the basis of the presence or absence of this enzyme.The cytochrome c oxidase oxidizes the test reagent and helps toidentify the oxidase positive bacteria.
2] Aerobic bacteria generally are oxidase positive. Somebacteria which are oxidase positive belong to Pseudomonas,Neisseria, Alcaligens, Vibrio, Pasteurella, Brucella etc, to name afew.
Oxidase positive bacteria contain cytochrome c oxidase and can,therefore, use oxygen to produce energy by converting O2 to H2O2and H2O with an electron transfer chain.
3] The reason for the bubbles not appearing may be the lack ofcatalase in the bacteria. Catalase enzyme mediates the breakdown ofH2O2 into O2 and water. The O2 is liberated as bubbles in theexperimental set-up. So, if O2 is not being formed, it means thereis not enough catalase to react with H2O2 and cause itsbreakdown.
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