biology

Microtox bioassay

Microtox bioassay 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 Microtox bioassay rather than just read about it. In short: Microtox is an in vitro testing system which uses bioluminescent bacteria (Allivibrio fischeri, formerly known as Vibrio fischeri) to detect toxic substances in different substrates such as water, air, soils and sediments. Allivibrio fischeri are non-pathogenic, marine, bacteria that luminesce as a natural part of their metabolism.

Key takeaways

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

Reference excerpt

Microtox is an in vitro testing system which uses bioluminescent bacteria (Allivibrio fischeri, formerly known as Vibrio fischeri) to detect toxic substances in different substrates such as water, air, soils and sediments. Allivibrio fischeri are non-pathogenic, marine, bacteria that luminesce as a natural part of their metabolism. When exposed to a toxic substance, the respiratory process of the bacteria is disrupted, reducing light output. Allivibrio fischeri have demonstrated high sensitivity across a wide variety of toxic substances. Response to toxicity is observed as a change in luminescence, which is a by-product of cellular respiration. This change can be used to calculate a percent inhibition of Allivibrio fischeri that directly correlates to toxicity.

Background Microtox was developed by Azur Environmental (formerly Microbics Corporation) in 1979 as a cost-effective alternative to toxicity tests available at the time. Prior to Microtox, the majority of toxicity tests available for water specifically focused on fish and daphnids. Since its inception, Microtox has become a standard method for testing the toxicity of water as well as other substrates such as soils and sediments. In recent years the Microtox technology and name have undergone various different ownerships. In 2011, Microtox and related technologies was acquired by Modern Water from Strategic Diagnostics Incorporated (SDIX) for approximately $4.5 million. Prior to SDIX, Microtox was owned by its original developers Azur Environmental. Microtox utilizes a bioluminescent bacteria (Allivibrio fischeri) to determine the toxicity of a particular substance and/or substrate. During cellular metabolism, these bacteria naturally emit light as a part of cellular respiration, which can be measured as luminescence. When exposed to toxic substances, a decrease in luminescence can be observed and percent change in luminescence can be directly correlated to toxicity. Allivibrio fischeri were specifically chosen, as these bacteria could be preserved by freeze-drying to increase shelf life and use. Both solid phase (soils and sediment) and aqueous acute toxicity testing (described below) can be conducted using this technology.

Materials

Analysers The Microtox Model 500 is a laboratory-based photometer that measures acute toxicity. This analyser is a temperature-controlled, self-calibrating biosensor measuring system that uses the bioluminescence of Allivibrio fischeri to determine the toxicity of contaminated water, or elutriates of contaminated soils and sediments. Microtox Continuous Toxicity Monitor (CTM) is a site-specific Microtox analyser that continuously measures the toxicity of a water source and provides results instantly. This fully automatic analyser has a broad detection range that can identify several thousand contaminants simultaneously whether or not there is knowledge of the source of contamination. This device has the ability to run continuously for up to 4 weeks, and is easy to operate and maintain. The DeltaTox II is a portable instrument that can be used to conduct acute toxicity and adenosine triphosphate (ATP) testing. Also known as the portable version of the Microtox Model 500, this device provides simple testing, uses small sample sizes, and is a cost-effective approach to analyzing water samples. This sensitive and rapid testing analyser has the ability to detect microbial contamination, as well as more than 2,700 different chemicals.

Reagent and solutions

Microtox model 500 and Microtox FX The shelf life for the Acute Reagent is two years and for the solutions is three years when stored properly. Microtox Acute Reagent is a freeze-dried culture of Allivibrio fischeri that is reconstituted prior to testing. It is recommended that the reagent be used within three hours of reconstitution. The sensitivity of the reagent may become altered after the recommended time period. Microtox Osmotic Adjustment Solution (MOAS) is a nontoxic solution that is made up of 22% sodium chloride (NaCl) and ultra-pure water. This solution is added to a sample to adjust the osmotic pressure to approximately 2% NaCl. Reconstitution Solution consists of specially prepared, nontoxic ultra-pure water. Diluent is a nontoxic solution that is made up of 2% NaCl in ultra-pure water. This solution is used for diluting the sample and the reagent, and also provides osmotic protection that is required by Allivibrio fischeri.

Methods

… excerpt ends here. Continue reading the full article.

Illustrations

Worked examples

Example 1 — a first encounter with Microtox bioassay

Start with the simplest possible case. Write down what Microtox bioassay 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 Microtox bioassay 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 Microtox bioassay 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 Microtox bioassay

In research: Microtox bioassay 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 Microtox bioassay 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: Microtox bioassay is common in secondary-school and first-year university syllabi. It links to neighbouring topics Aquatic ecology, Ecotoxicology, Toxicology tests, so understanding it makes those chapters shorter.
In everyday life: Look for Microtox bioassay 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 Microtox bioassay in 20 minutes

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

Frequently asked questions

What is Microtox bioassay in simple terms?

Why does Microtox bioassay 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 Microtox bioassay?

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 Microtox bioassay.