chemistry

Oxidase test

Oxidase test is a chemistry topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Oxidase test rather than just read about it. In short: The oxidase test is used to determine whether an organism possesses the cytochrome c oxidase enzyme. The test is used as an aid for the differentiation of Neisseria, Moraxella, Campylobacter and Pasteurella species (oxidase positive).

Key takeaways

Oxidase test belongs to chemistry; place it in that map before memorising details.
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Connect Oxidase test to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Oxidase test from memory before moving on to harder problems.

Reference excerpt

The oxidase test is used to determine whether an organism possesses the cytochrome c oxidase enzyme. The test is used as an aid for the differentiation of Neisseria, Moraxella, Campylobacter and Pasteurella species (oxidase positive). It is also used to differentiate pseudomonads from related species.

Classification Strains may be either oxidase-positive (OX+) or oxidase-negative (OX-).

OX+ OX+ normally means the bacterium contains cytochrome c oxidase (also known as Complex IV) and can therefore use oxygen for energy production by converting O2 to H2O2 or H2O with an electron transfer chain. The Pseudomonadaceae are typically OX+. The Gram-negative diplococci Neisseria and Moraxella are oxidase-positive. Many Gram-negative, spiral curved rods are also oxidase-positive, which includes Helicobacter pylori, Vibrio cholerae, and Campylobacter jejuni.

Oxidase variable Legionella pneumophila may be oxidase-positive.

OX− OX− normally means the bacterium does not contain cytochrome c oxidase and, therefore, either cannot use oxygen for energy production with an electron transfer chain or employs a different cytochrome for transferring electrons to oxygen. Enterobacteriaceae are typically OX−.

Mechanism

The test uses disks impregnated with reagents such as N,N,N′,N′-tetramethyl-p-phenylenediamine, TMPD (or N,N-dimethyl-p-phenylenediamine, DMPD, which is another redox indicator). The reagent is a dark-blue to maroon color when oxidized, and colorless when reduced. Oxidase-positive bacteria possess cytochrome oxidase or indophenol oxidase (an iron-containing hemoprotein). These both catalyze the transport of electrons from donor compounds (NADH) to electron acceptors (usually oxygen). The test reagent TMPD acts as an artificial electron donor for the enzyme oxidase. The oxidized reagent forms the colored compound indophenol blue. The cytochrome system is usually only present in aerobic organisms that are capable of using oxygen as the terminal electron acceptor. The end-product of this metabolism is either water or hydrogen peroxide (broken down by catalase).

Procedures Wet each disk with about four inoculating loops of deionized water. Use a loop to aseptically transfer a large mass of pure bacteria to the disk. Observe the disk for up to three minutes. If the area of inoculation turns dark-blue to maroon to almost black, then the result is positive. If a color change does not occur within three minutes, the result is negative. In alternative manner, live bacteria cultivated on trypticase soy agar plates may be prepared using sterile technique with a single-line streak inoculation. The inoculated plates are incubated at 37 °C for 24–48 hours to establish colonies. Fresh bacterial preparations should be used. After colonies have grown on the medium, 2-3 drops of the reagent DMPD are added to the surface of each organism to be tested.

A positive test (OX+) will result in a color change violet to purple, within 10–30 seconds. A negative test (OX-) will result in a light-pink or absence of coloration.

References

American Society for Microbiology, Oxidase Test Protocol. 2013. ASM MicrobeLibrary, 1–9. Cheng W J, Lin C W, Wu T G, Su C S, Hsieh M S. 2013. Calibration of glucose oxidase-based test strips for capillary blood measurement with oxygen saturated venous blood samples. Clinica Chimica Acta. 415, 152–157. Corchia L, Hubault R, Quinquenel B, N'Guyen. 2015. Rapidly Evolving Conjunctivitis Due to Pasteurella Multocida, Occurring after Direct Inoculation with Animal Droplets in an Immuno-compromised Host. BMC Ophthalmology 15.1, 21. Floch C, Alarcon-Gutiérrez E, Criquet S. 2007. ABTS assay of phenol oxidase activity in soil. Journal of Microbiological Methods. 71, 319–324. Gaby W L, Hadley C. 1957. Practical laboratory test for the identification of Pseudomonas aeruginosa. Journal of bacteriology. 74, 356–358. Gilani M, Munir T, Latif M, Gilani M, Rehman S, Ansari M, Hafeez A, Najeeb S, Saad N. 2015. In Vitro Efficacy of Doripenem against Pseudomonas Aeruginosa and Acinetobacter Baumannii by E-test. Journal of the College of Physicians and Surgeons Pakistan 25, 726–729. Kuss S, Tanner E E L, Ordovas-Montanes M, Compton R G. 2017. Electrochemical Recognition and Quantification of Cytochrome C Expression in and Aerobe/anaerobe Using, ','-tetramethyl—phenylene-diamine (TMPD). Chemical Science 8.11, 7682–7688. Web. Ivanova N V, Zemlak T S, Hanner R H, Hebert P D N. 2007. Universal primer cocktails for fish DNA barcoding. Molecular Ecology Notes. 7, 544–54. Prince C. 2009. Practical Manual of Medical Microbiology (Jaypee Brothers Medical Publishers (P) Ltd.) 112–112. Shields P, Cathcart L. 2013. Oxidase Test Protocol - Library. American Society for Microbiology, ASM MicrobeLibrary, 1–5. Steel K J. 1961. The Oxidase Reaction as a Taxonomic Tool. Journal of General Microbiology. 25, 297–306. Zanderigo F et al. 2018. [11C]Harmine Binding to Brain Monoamine Oxidase A: Test-Retest Properties and Noninvasive Quantification. Molecular Imaging and Biology. 20, 667–681.

External links Oxidase test video Oxidase Test Procedure

Illustrations

Worked examples

Example 1 — a first encounter with Oxidase test

Start with the simplest possible case. Write down what Oxidase test claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In chemistry, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Oxidase test before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Oxidase test ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Oxidase test

In research: Oxidase test appears in chemistry research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Oxidase test in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Oxidase test is common in secondary-school and first-year university syllabi. It links to neighbouring topics Biochemistry detection reactions, Microbiology techniques, so understanding it makes those chapters shorter.
In everyday life: Look for Oxidase test outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Oxidase test in 20 minutes

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Frequently asked questions

What is Oxidase test in simple terms?

Why does Oxidase test matter?

Because it connects several chemistry ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Oxidase test?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Oxidase test.