chemistry

Thiosulfate–citrate–bile salts–sucrose agar

Thiosulfate–citrate–bile salts–sucrose agar 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 Thiosulfate–citrate–bile salts–sucrose agar rather than just read about it. In short: Thiosulfate–citrate–bile salts–sucrose agar, or TCBS agar, is a type of selective agar culture plate that is used in microbiology laboratories to isolate Vibrio species. TCBS agar is highly selective for the isolation of V. cholerae and V. parahaemolyticus as well as other Vibrio species.

Key takeaways

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

Reference excerpt

Thiosulfate–citrate–bile salts–sucrose agar, or TCBS agar, is a type of selective agar culture plate that is used in microbiology laboratories to isolate Vibrio species. TCBS agar is highly selective for the isolation of V. cholerae and V. parahaemolyticus as well as other Vibrio species. Apart from TCBS agar, other rapid testing dipsticks like immunochromatographic dipsticks are also used in endemic areas such as Asia, Africa and Latin America. Though, TCBS agar study is required for confirmation. This becomes immensely important in cases of gastroenteritis caused by Campylobacter species, whose symptoms mimic those of cholera. Since no yellow bacterial growth is observed in case of Campylobacter species on TCBS agar, chances of incorrect diagnosis can be rectified. TCBS agar contains high concentrations of sodium thiosulfate and sodium citrate to inhibit the growth of Enterobacteriaceae. Inhibition of gram-positive bacteria is achieved by the incorporation of ox gall, which is a naturally occurring substance containing a mixture of bile salts and sodium cholate, a pure bile salt. Sodium thiosulfate also serves as a sulfur source and its presence, in combination with ferric citrate, allows for the easy detection of hydrogen sulfide production. Saccharose (sucrose) is included as a fermentable carbohydrate for metabolism by Vibrio species. The alkaline pH of the medium enhances the recovery of V. cholerae and inhibits the growth of others. Thymol blue and bromothymol blue are included as indicators of pH changes.

Formula

Approximate amounts per liter Yeast extract 5.0 g Proteose Peptone 10.0 g Sodium thiosulfate 10.0 g Sodium citrate 10.0 g Ox gall 5.0 g Sodium cholate 3.0 g Saccharose 20.0 g Sodium chloride 10.0 g Ferric citrate 1.0 g Bromothymol blue 0.04 g Thymol blue 0.04 g Agar 15.0 g pH 8.6 ± 0.2 @ 25 °C

Expected results Typical colony morphology V. cholerae: Large yellow colonies. V. parahaemolyticus: Colonies with blue to green centers. V. alginolyticus: Large yellow mucoidal colonies. V. harveyi / V. fischeri: Greyish-green to bluish-green colonies which show luminescence in dark. Older colonies fail to show bioluminescence. Proteus / Enterococci: Partial inhibition. If growth, colonies are small and yellow to translucent. Pseudomonas / Aeromonas: Partial inhibition. If growth, colonies are blue. Bacteria that are not Vibrio but produce hydrogen sulfide grow as small black colonies. This is because the hydrogen sulphide produced from thiosulphate, which acts as a source of sulphur and creates a reduced oxygen tension in which Vibrio can grow due to its facultative anaerobic nature, combines with ferric ions from ferric citrate to produce ferric sulphide, which is black. TCBS agar is both selective and differential. It is highly selective for Vibrio species and differential due to the presence of sucrose and the dyes. Sucrose fermentation produces acid, which converts the colour of bromothymol blue or thymol blue. Two dyes rather than one make the medium produce an array of yellow, green, or blue so that differentiating among various Vibrio species is possible.

Control of Acanthaster planci TCBS agar has also been used to control outbreaks of the crown-of-thorns sea star (Acanthaster planci), which is a threat to coral reefs. Single injections lead to deaths of sea stars within 24 hours, with symptoms of "discolored and necrotic skin, ulcerations, loss of body turgor, accumulation of colourless mucus on many spines especially at their tip, and loss of spines. Blisters on the dorsal integument broke through the skin surface and resulted in large, open sores that exposed the internal organs." This was due to promotion of the growth of naturally occurring Vibrio species to high densities, with subsequent symbiont imbalance.

References

Illustrations

Worked examples

Example 1 — a first encounter with Thiosulfate–citrate–bile salts–sucrose agar

Start with the simplest possible case. Write down what Thiosulfate–citrate–bile salts–sucrose agar 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 Thiosulfate–citrate–bile salts–sucrose agar 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 Thiosulfate–citrate–bile salts–sucrose agar 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 Thiosulfate–citrate–bile salts–sucrose agar

In research: Thiosulfate–citrate–bile salts–sucrose agar 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 Thiosulfate–citrate–bile salts–sucrose agar 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: Thiosulfate–citrate–bile salts–sucrose agar is common in secondary-school and first-year university syllabi. It links to neighbouring topics Bacteriology, Biochemistry detection reactions, Microbiological media, so understanding it makes those chapters shorter.
In everyday life: Look for Thiosulfate–citrate–bile salts–sucrose agar 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.

Ask Teacher Smith questions about this articleOpens your AI tutor with a question about “Thiosulfate–citrate–bile salts–sucrose agar” →

Affiliate

Preply — study more efficiently by working with a personal tutor. 50% off.

How to study Thiosulfate–citrate–bile salts–sucrose agar in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Thiosulfate–citrate–bile salts–sucrose agar 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 Thiosulfate–citrate–bile salts–sucrose agar out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Thiosulfate–citrate–bile salts–sucrose agar in simple terms?

Why does Thiosulfate–citrate–bile salts–sucrose agar 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 Thiosulfate–citrate–bile salts–sucrose agar?

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 Thiosulfate–citrate–bile salts–sucrose agar.