biology

Löwenstein–Jensen medium

Löwenstein–Jensen medium is a biology 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 Löwenstein–Jensen medium rather than just read about it. In short: Löwenstein–Jensen medium, more commonly known as LJ medium, is a growth medium specially used for culture of Mycobacterium species, notably Mycobacterium tuberculosis. When grown on LJ medium, M. tuberculosis appears as brown, granular colonies (sometimes called "buff, rough and tough").

Key takeaways

Löwenstein–Jensen medium belongs to biology; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Löwenstein–Jensen medium to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Löwenstein–Jensen medium from memory before moving on to harder problems.

Reference excerpt

Löwenstein–Jensen medium, more commonly known as LJ medium, is a growth medium specially used for culture of Mycobacterium species, notably Mycobacterium tuberculosis. When grown on LJ medium, M. tuberculosis appears as brown, granular colonies (sometimes called "buff, rough and tough"). The medium must be incubated for a significant length of time, usually four weeks, due to the slow doubling time of M. tuberculosis (15–20 hours) compared with other bacteria. The medium is named after the Austrian pathologist Ernst Löwenstein (1878–1950) and the Danish medical doctor Kai Adolf Jensen (1894–1971).

Composition The usual composition as applicable to M. tuberculosis is:

Malachite green Glycerol Asparagine Potato starch Coagulated eggs Mineral salt solution Potassium dihydrogen phosphate Magnesium sulfate Sodium citrate The original formulation included starch, which was later found to be unnecessary, so omitted. Low levels of penicillin and nalidixic acid are also present in LJ medium to inhibit growth of Gram-positive and Gram-negative bacteria, to limit growth to Mycobacterium species only. Presence of malachite green in the medium inhibits most other bacteria. It is disinfected and solidified by a process of inspissation. Presence of glycerol enhances the growth of M. tuberculosis. If the slopes are made on test tubes, they must be stored in cold and used within a month. For cultivation of M. bovis, glycerol is omitted and sodium pyruvate is added. The medium appears green, opaque, and opalescent.

Uses

For diagnosis of mycobacterial infections For testing antibiotic susceptibility of isolates For differentiating different species of Mycobacterium (by colony morphology, growth rate, biochemical characteristics, and microscopy)

Alternatives

Alternative culture media While LJ medium is the most popular means of culturing mycobacteria, as recommended by the International Union against Tuberculosis, several alternative media have been investigated.

Solid media Egg-based – Petragnani medium and Dorset medium Middlebrook 7H10 agar Middlebrook 7H11 agar Blood-based – Tarshis medium Serum-based – Loeffler medium Potato-based – Pawlowsky medium

Liquid media Dubos' medium Middlebrook 7H9 broth Proskauer and Beck's medium Sula's medium Sauton's medium

Rapid detection techniques The chief limitation of culture-based techniques is the time it takes to culture positivity, which can be several months. Several new molecular technologies have emerged in recent years to secure more speedy confirmation of diagnosis.

Polymerase chain reaction GeneXpert MTB/RIF Loop-mediated isothermal amplification

See also Kinyoun stain Tuberculosis Tuberculosis diagnosis Ziehl-Neelsen stain

References

Illustrations

Worked examples

Example 1 — a first encounter with Löwenstein–Jensen medium

Start with the simplest possible case. Write down what Löwenstein–Jensen medium claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In biology, 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 Löwenstein–Jensen medium 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 Löwenstein–Jensen medium 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 Löwenstein–Jensen medium

In research: Löwenstein–Jensen medium appears in biology 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 Löwenstein–Jensen medium 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: Löwenstein–Jensen medium is common in secondary-school and first-year university syllabi. It links to neighbouring topics Microbiological media, so understanding it makes those chapters shorter.
In everyday life: Look for Löwenstein–Jensen medium 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 Löwenstein–Jensen medium in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Löwenstein–Jensen medium means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Löwenstein–Jensen medium out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Löwenstein–Jensen medium in simple terms?

Why does Löwenstein–Jensen medium matter?

Because it connects several biology 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 Löwenstein–Jensen medium?

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 Löwenstein–Jensen medium.