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Microaerophile

Microaerophile 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 Microaerophile rather than just read about it. In short: A microaerophile is a microorganism that requires environments containing lower levels of dioxygen than those present in the atmosphere (i.e. < 21% O2; typically 2–10% O2) for optimal growth. A more restrictive interpretation requires the microorganism to be obligate in this requirement.

Microaerophile — main illustration
Microaerophile — illustration

Key takeaways

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

Reference excerpt

A microaerophile is a microorganism that requires environments containing lower levels of dioxygen than those present in the atmosphere (i.e. < 21% O2; typically 2–10% O2) for optimal growth. A more restrictive interpretation requires the microorganism to be obligate in this requirement. Many microaerophiles are also capnophiles, requiring an elevated concentration of carbon dioxide (e.g. 10% CO2 in the case of Campylobacter species). The original definition of a microaerophile has been criticized for being too restrictive and not accurate enough compared to similar categories. The broader term microaerobe has been coined to describe microbes able to respire oxygen "within microoxic environments by using high-affinity terminal oxidase".

Culture Microaerophiles are traditionally cultivated in candle jars. Candle jars are containers into which a lit candle is introduced before sealing the container's airtight lid. The candle's flame burns until extinguished by oxygen deprivation, creating a carbon dioxide-rich, oxygen-poor atmosphere. Newer oxystat bioreactor methods allow for more precise control of gas levels in the microaerobic environment, using a probe to measure the oxygen concentration or redox potential in real time. Ways to control oxygen intake include gas-generating packs and gas exchange. As oxystat bioreactors are expensive to buy and run, lower-cost solutions have been devised. For example, the Micro-Oxygenated Culture Device (MOCD) is a system involving ordinary flasks, oxygen-permeable tubes, sensors, and water pumps. Aeration is done by pumping the culture medium through the tubes.

Examples A wide variety of microaerobic conditions exist in the world: in human bodies, underwater, etc. Many bacteria from these sources are microaerobes, some of which are also microaerophiles.

Some members of Campylobacterales are microaerophilic: Campylobacter species are microaerophilic. Helicobacter pylori (previously identified as a Campylobacter), a species of Campylobacterota that has been linked to peptic ulcers and some types of gastritis Many members of Lactobacillus sensu lato (see Lactobacillaceae) are microaerophiles. As facultative anaerobes, they do survive anaerobic conditions, but grow better with a little oxygen. Magnetospirillum gryphiswaldense and Magnetospira sp. QH-2 are aquatic microaerophilic magnetotactic bacteria. The formation of magnetite in such bacteria in general require microaerobic conditions.

See also Aerobic respiration Anaerobic respiration Facultative anaerobe Fermentation Obligate aerobe Obligate anaerobe Oxygenation (environmental)

References

External links Characterization of an unclassified microaerophilic bacterium associated with gastroenteritis.

Illustrations

Microaerophile: Anaerobic bacteria can be identified by growing them in test tubes of thioglycollate broth: 1: Obligate aerobes need oxygen because they cannot ferment or respire anaerobically. They gather at the top of the tube where the oxygen concentration is highest. 2: Obligate anaerobes are poisoned by oxygen, so they gather at the bottom of the tube where the oxygen concentration is lowest. 3: Facultative anaerobes can grow with or without oxygen because they can metabolise energy aerobically or anaerobically. They gather mostly at the top because aerobic respiration generates more ATP than either fermentation or anaerobic respiration. 4: Microaerophiles need oxygen because they cannot ferment or respire anaerobically. However, they are poisoned by high concentrations of oxygen. They gather in the upper part of the test tube but not the very top. 5: Aerotolerant organisms do not require oxygen as they metabolise energy anaerobically. Unlike obligate anaerobes however, they are not poisoned by oxygen. They can be found evenly spread throughout the test tube.
Anaerobic bacteria can be identified by growing them in test tubes of thioglycollate broth: 1: Obligate aerobes need oxygen because they cannot ferment or respire anaerobically. They gather at the top of the tube where the oxygen concentration is highest. 2: Obligate anaerobes are poisoned by oxygen, so they gather at the bottom of the tube where the oxygen concentration is lowest. 3: Facultative anaerobes can grow with or without oxygen because they can metabolise energy aerobically or anaerobically. They gather mostly at the top because aerobic respiration generates more ATP than either fermentation or anaerobic respiration. 4: Microaerophiles need oxygen because they cannot ferment or respire anaerobically. However, they are poisoned by high concentrations of oxygen. They gather in the upper part of the test tube but not the very top. 5: Aerotolerant organisms do not require oxygen as they metabolise energy anaerobically. Unlike obligate anaerobes however, they are not poisoned by oxygen. They can be found evenly spread throughout the test tube.

Worked examples

Example 1 — a first encounter with Microaerophile

Start with the simplest possible case. Write down what Microaerophile 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 Microaerophile 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 Microaerophile 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 Microaerophile

In research
Microaerophile 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 Microaerophile 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
Microaerophile is common in secondary-school and first-year university syllabi. It links to neighbouring topics Microbial growth and nutrition, Microbial metabolism, Microbiology stubs, so understanding it makes those chapters shorter.
In everyday life
Look for Microaerophile 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 Microaerophile in 20 minutes

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

Frequently asked questions

What is Microaerophile in simple terms?

A microaerophile is a microorganism that requires environments containing lower levels of dioxygen than those present in the atmosphere (i.e. < 21% O2; typically 2–10% O2) for optimal growth. A more restrictive interpretation requires the microorganism to be obligate in this requirement.

Why does Microaerophile 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 Microaerophile?

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 Microaerophile.

Tags

  • Microbial growth and nutrition
  • Microbial metabolism
  • Microbiology stubs

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