Question

BIOL2516K Spring 2020 Week 9 Results and Homework Name 2. What does the oxidase test determine? Would you expect positive results in both aerobic and anaerobic species? 3. You accidentally mixed up the labeling of 2 pure cultures you incubated overnight. One is a Staphylococcus species and the other is a Streptococcus species. What could you do to identify the 2 tubes? Staphylococcus species are facultative anaerobes and Streptococcus species are aerotolerant anaerobes could you do to identibus species and the other iedes you incubated overnight 4. Your instructor advises you that the bacterial culture given undergoes nitrate reduction. You inoculate nitrate broth and incubate. What possible results could you observe in the nitrate reduction test?

Answer 1

2. The oxidase test is used to identify bacteria that produce cytochrome c oxidase, an enzyme of the bacterial electron transport chain. When present, the cytochrome c oxidase oxidizes the reagent tetramethyl-p-phenylenediamine to indophenol a purple colour end product. When the enzyme is not present, the reagent remains reduced and is colourless.

3. The main criterion for differentiation between Staphylococcus and Streptococcus genera is the catalase test. Staphylococci are catalase-positive whereas Streptococci are Catalase negative. Catalase is an enzyme used by bacteria to induce the reaction of reduction of hydrogen peroxide into water and oxygen.

4. The nitrate reduction test tests for a bacterial strain's ability to reduce nitrate to nitrite or further compounds. A positive test means the organism was able to reduce nitrate to nitrite, a positive result for nitrate reduction.