biology

Interspecies quorum sensing

Interspecies quorum sensing 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 Interspecies quorum sensing rather than just read about it. In short: Interspecies quorum sensing is a type of quorum sensing in which bacteria send and receive signals to other species besides their own. This is accomplished by the secretion of signaling molecules which trigger a response in nearby bacteria at high enough concentrations.

Key takeaways

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

Reference excerpt

Interspecies quorum sensing is a type of quorum sensing in which bacteria send and receive signals to other species besides their own. This is accomplished by the secretion of signaling molecules which trigger a response in nearby bacteria at high enough concentrations. Once the molecule hits a certain concentration it triggers the transcription of certain genes such as virulence factors. It has been discovered that bacteria can not only interact via quorum sensing with members of their own species but that there is a kind of universal molecule that allows them to gather information about other species as well. This universal molecule is called autoinducer 2 or AI-2. AI-2 was first discovered in the light producing system of the bacteria Vibrio harveyi. The pathway that induces V. harveyi luminescence is controlled by two parallel pathways. The first pathway uses a typical AI-1 homoserine lactone signaling molecule. However the bacteria were also found to recognize a second auto inducer AI-2. Scientist also found that V. harveyi luminescence could be induced by 75 other bacterial species AI-2 molecules. This discovery led to the proposal of AI-2 as a universal form of communication between bacteria species. In addition to information about cell densities AI-2 can provide information on the growth phase and prosperity of cells in a population. It has a greater ability to store information than other quorum-sensing molecules because its production is tied to cell growth. The production of AI-2 peaks in late log phase for many bacteria. The structure of AI-2 was discovered recently to be a fused 2-member ring with boron bridging the gap between the diesters. The enzyme LuxS is responsible for AI-2 synthesis. The gene encoding for LuxS has been detected in 35 of the 89 bacterial genomes sequenced and in all of the bacteria the gene had little variation. In every bacterium found so far that produces the AI-2 signaling molecule the LuxS gene was also found. There are three enzymes that make DPD (4,5-dihydroxy 2,3 pentanedione) which is the substrate LuxS uses to make AI-2. The pathway for synthesizing AI-2 was found to be identical in V. harveyi, Escherichia coli, Salmonella typhimurium, V. cholerae, and Enterococcus faecalis providing further evidence that this molecule may be a universal signal among bacteria. Shigella flexneri use AI-2 to mediate virulence. The major virulence factor in Shigella is the plasmid vir B. The AI-2 signaling pathway was shown to be responsible for the observed peak of vir B. Although it was determined that AI-2 is not crucial for virulence that it does increase the expression of the plasmid. AI-2 also regulates the virulence of enteroinvasive and enterohemoragic E. coli. It is likely the high concentrations of AI-2 produced by normal gut flora effect the production of AI-2 in Shigella and its subsequent virulence. AI-2 is required for the biofilm formation in Porphyromonas gingivalis and Streptococcus gordonii. S. gordonii is a major cause of dental plaque and its adherence is essential for many other pathogenic bacteria to also adhere to teeth. P. gingivalis causes periodontal disease. If neither bacteria possess a functional copy of the LuxS gene they cannot form a biofilm. However, if either one of the bacteria has the LuxS gene they can form biofilms, suggesting again this molecule is used for communication between unrelated species. Other bacterial uses for AI-2

Clostridium perfringens – regulates toxin production Photorhabdus luminescens – controls the timing of antibiotics Vibrio cholerae – used in the pathogenic cascade Since the LuxS enzyme is not present in eukaryotes it is a good potential target for antibiotics. Also AI-2 signaling seems to control many virulence factors in bacteria so blocking this signal could lead to new ways to control bacterial infections such as cholera. Since the AI-2 molecule seems to be involved in the virulence cascade if we could block the uptake of AI-2 then we could potentially stop the virulence cascade. Fungi also communicate with one another. Quorum-sensing molecules (QSMs) from fungi include farnesol, tyrosol, phenylethanol, and tryptophol. QSMs have been studied in Candida albicans, C. dubliniensis, Aspergillus niger, A. nidulans, and Fusarium graminearum. QSMs can include morphogenesis, germination, apotopsis, pathogenicity, and biofilm structures.

Worked examples

Example 1 — a first encounter with Interspecies quorum sensing

Start with the simplest possible case. Write down what Interspecies quorum sensing 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 Interspecies quorum sensing 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 Interspecies quorum sensing 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 Interspecies quorum sensing

In research: Interspecies quorum sensing 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 Interspecies quorum sensing 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: Interspecies quorum sensing is common in secondary-school and first-year university syllabi. It links to neighbouring topics Bacteriology, so understanding it makes those chapters shorter.
In everyday life: Look for Interspecies quorum sensing 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 Interspecies quorum sensing in 20 minutes

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

Frequently asked questions

What is Interspecies quorum sensing in simple terms?

Why does Interspecies quorum sensing 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 Interspecies quorum sensing?

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 Interspecies quorum sensing.