Ex. 15 Oxidase Test

Objectives: ??

Cytochrome oxidases help with transfer of electrons from cytochromes to oxygen.

Electron Transport Phosphorylation

Textbook Fig 5.16

Oxidase Test

• Determines presence of certain cytochrome oxidases

• Use whenever Gram-neg. bacteria have to be identified

• When test reagent gets oxidized it changes color.

• Oxidase test is positive if color change within 15 seconds!

Only use on young cultures

Table 15-1: Oxidase Test Results and Interpretation

Result Interpretation Symbol

Dark blue within 15 seconds Cytochrome c oxidase is present +

No color change to blue or blue after 15 seconds

Cytochrome c oxidase is absent

Oxistrip

The End

Materials needed per table: Oxidase reagent (bottle with

dropper) Small pieces of paper towel sterile Q-tips (2 per student)

Pure slant culture needed per table:1. E. coli2. Pseudomonas aeruginosa

Each student should individually do the oxidase test for both bacterial species.