science

Tracheal cytotoxin

Tracheal cytotoxin is a science 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 Tracheal cytotoxin rather than just read about it. In short: Tracheal cytotoxin (TCT) is a 921 dalton glycopeptide released by Bordetella pertussis, Vibrio fischeri (as a symbiosis chemical), and Neisseria gonorrhoeae (among other peptidoglycan-derived cytotoxins it produces). It is a soluble piece of peptidoglycan (PGN) found in the cell wall of all gram-negative bacteria, but only some bacteria species release TCT due to inability to recycle this piece of anhydromuropeptide.

Key takeaways

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

Reference excerpt

Tracheal cytotoxin (TCT) is a 921 dalton glycopeptide released by Bordetella pertussis, Vibrio fischeri (as a symbiosis chemical), and Neisseria gonorrhoeae (among other peptidoglycan-derived cytotoxins it produces). It is a soluble piece of peptidoglycan (PGN) found in the cell wall of all gram-negative bacteria, but only some bacteria species release TCT due to inability to recycle this piece of anhydromuropeptide.

History In 1980, it was discovered that B. pertussis could attach to hamster tracheal epithelial (HTE) cells, and also, that the supernatant from the cultured bacterium could disrupt the cell cycle of uninfected cells. This prompted the scientists W. E. Goldman, D. G. Klapper, and J. B. Baseman to isolate and characterize a novel substance from B. pertussis supernatant. The novel disaccharide tetrapeptide that they had purified showed toxicity for HTE cells and tracheal ring cultures. Subsequently, they named the newly sequestered molecule tracheal cytotoxin (TCT).

Structure

TCT is a soluble piece of peptidoglycan (PGN) found in the cell wall of all gram-negative bacteria. Like all PGNs, TCT is composed of a disaccharide and a peptide chain. The IUPAC name for TCT is N-acetylglucosaminyl-1,6-anhydro-N-acetylmuramyl-(L)-alanyl-γ-(D)-glutamyl-mesodiaminopimelyl-(D)-alanine. It is classified as a DAP (diaminopimelic acid)-type PGN due to the third amino group within the chain being a diaminopimelyl peptide.

The DAP residue is responsible for directly bonding to the D-alanine peptide of another PGN molecule, thus aiding TCT's attachment within the cell wall. The DAP portion of TCT also implies importance in cytopathogenicity as analogs lacking DAP show a significant reduction in toxicity.

Mechanism of pathogenesis Most Gram-negative bacteria keep TCT within the cell wall by using a PGN-transporter protein known as AmpG. However, B. pertussis is not capable of recycling PGNs via AmpG and thus, TCT escapes into the surrounding environment. Also, TCT is constitutively released by B. pertussis.

The first murine-model studies using TCT involved treatment of hamster tracheal cells. These experiments alluded to TCT's role in ciliostasis and cellular extrusion of ciliated hamster cells. Also, HTE cells had a markedly reduced level of DNA synthesis post-treatment with TCT. While previous studies using murine models reported evidence of TCT causing ciliostasis, in vitro studies using human tracheal cells have shown that TCT does not affect ciliary beat frequency of living cells, but instead causes damage and eventual extrusion of ciliated cells. In gonorrhea infections, vaginal ciliated epithelial cells have also displayed the same cytopathogenic effects due to TCT recognition. The extensive damage to ciliated epithelial tissue caused by TCT results in major disruption to the ciliary escalator; an important asset of the host's non-specific defenses. This disruption hinders the host's ability to remove mucous and foreign microbes from the epithelial tissue. Paroxysmal cough, e.g. whooping cough, is a direct symptom of said mucous build-up due to ciliated tissue damage. NOD-1 recognition and the presence of Lipooligosaccharide (LOS) are two factors that modulate the effect of TCT. NOD-1 is a pattern recognition receptor that detects peptidoglycan. This receptor reacts weakly to TCT in humans, but robustly in mice. TCT is thought to work synergistically with LOS to mediate an inflammatory response, thus causing damage to ciliated epithelial cells. Notably, the human pathogens (B. pertussis and N. gonorrhea) that produce excess TCT, causing damage to cilia also both produce LOS in their outer membrane.

Effect on immune system TCT has been classified as an adjuvant molecule because of the stimulating effects it has on the immune system. Cellular damage associated with TCT is thought to be a result of increased levels of nitric oxide (NO) secretion by mucosal cells as part of an innate defense response to extracellular lipopolysaccharide (LPS) and TCT. In humans, peptidoglycan recognition proteins, e.g. PGRPIαC, appear to bind with TCT and consequently induce the Tumor Necrosis Factor Receptor (TNFR) pathway. Studies using murine macrophages have shown that TCT encourages cytokine secretion, probably through the NOD1 receptor. As a pleiotropic toxin, TCT also acts as a pyrogen and as a stimulant of slow-wave sleep. Peptidoglycan recognition protein 4 (PGLYRP4), in mammals (mice), interacts with TCT and reduces damage from pertussis inflammation. This molecule has similar immune-eliciting properties in Drosophila, where a pair of PGRPs perform the recognition.

References

External links Ligand entry in the Protein Data Bank: MLD Entry in MetaCyc: CPD0-1080

Illustrations

Worked examples

Example 1 — a first encounter with Tracheal cytotoxin

Start with the simplest possible case. Write down what Tracheal cytotoxin claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, 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 Tracheal cytotoxin 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 Tracheal cytotoxin 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 Tracheal cytotoxin

In research: Tracheal cytotoxin appears in science 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 Tracheal cytotoxin 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: Tracheal cytotoxin is common in secondary-school and first-year university syllabi. It links to neighbouring topics Bacterial toxins, Glycopeptides, so understanding it makes those chapters shorter.
In everyday life: Look for Tracheal cytotoxin 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 Tracheal cytotoxin in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Tracheal cytotoxin 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 Tracheal cytotoxin out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Tracheal cytotoxin in simple terms?

Why does Tracheal cytotoxin matter?

Because it connects several science 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 Tracheal cytotoxin?

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 Tracheal cytotoxin.