biology

Levilactobacillus brevis

Levilactobacillus brevis 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 Levilactobacillus brevis rather than just read about it. In short: Levilactobacillus brevis is a gram-positive, rod shaped species of lactic acid bacteria which is heterofermentative, creating CO2, lactic acid and acetic acid or ethanol during fermentation. L. brevis is the type species of the genus Levilactobacillus (previously L. brevis group), which comprises 24 species.[1] [2] It can be found in many different environments, such as fermented foods, and as normal microbiota.

Key takeaways

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

Reference excerpt

Levilactobacillus brevis is a gram-positive, rod shaped species of lactic acid bacteria which is heterofermentative, creating CO2, lactic acid and acetic acid or ethanol during fermentation. L. brevis is the type species of the genus Levilactobacillus (previously L. brevis group), which comprises 24 species.[1] [2] It can be found in many different environments, such as fermented foods, and as normal microbiota. Ingestion has been shown to improve human immune function, and it has been patented several times. Normal gut microbiota L. brevis is found in human intestines, vagina, and feces.

History E.B. Fred, W.H. Peterson, and J.A. Anderson initially discovered the species in 1921 and the it was categorized based on the ability to metabolize certain carbon compounds such as the sugars. This early study showed that this can produce acetic acid, carbon dioxide and large amounts of mannitol. Mannitol which is another carbon source that can be used to produce lactic acid.

Growth and metabolism L. brevis has been shown to actively transport glucose and galactose. When fructose was used as a carbon source there was only some growth and L. brevis was able to partially metabolize the fructose to mannitol. There are some strains that poorly metabolize glucose but prefer disaccharides as carbon source. By using the fermentation pathway the result is lactic acid and acetic acid. It appears that under high temperature conditions, 50°C and in acidic environments the survival of this bacteria is longer than most bacteria under acidic conditions, the bacteria can live about 45 minutes. Antibiotic resistance is acquired through conjugation, a method of bacterial reproduction. Conjugation permits a sharing of DNA allowing the bacterium to identify various antibiotics through exposure and this information is passed down through replication between bacteria.

L. brevis produces more organic acids, specifically acetic acid and ethanol. This means that this bacterium produces an increased acidic environment and alcohol. Growth conditions all depend on the location of the bacterium within the intestines. It does seem that they are unable to significantly replicate in anaerobic environments. L. brevis is heterofermentative and uses the phosphoketolase pathway to metabolize pentoses and hexoses.

Food preservation L. brevis is found in food such as sauerkraut and pickles. It is also one of the most common causes of beer spoilage. The hop, which is an antimicrobial bitter flavoring agent in beer, fails to suppress some strains of L. brevis because they produce a transporter that pumps the active agents of hops out of the bacterial cell. Major metabolites of L. brevis include lactic acid and ethanol. Strains of L. brevis and L. hilgardii have been found to produce the biogenic amines tyramine, which is found by the fermentation metabolic pathway and is commonly found in spoiled or fermented foods and phenylethylamine, which is found in chocolates but can also produce a fishy odor in other foods. L. brevis is one of the major lactobacilli found in water kefir grains, and has been identified as one of the species responsible for the production of the polysaccharide (dextran and kefiran) that forms the grains.

Microbial physiology As a bacterium there are some physical attributes of L. brevis that are common for all bacteria. Gram-positive bacteria consists of an external plasma membrane, followed by periplasmic space and finally a peptidoglycan layer, which faces the interior of the bacteria. The external plasma membrane is very important for bacteria because this is how cells recognize the possible pathogenesis of the bacteria. Peptidoglycan is also called murein and is made up of a series of sugars and amino acid monomers. Within gram-positive bacteria the peptidoglycan layer is much thicker than gram-negative bacteria. The actual lattice that comprises peptidoglycan is referred to as the S-layer; this lattice is linked to the peptidoglycan layer. However, the S-layer is normally lost when processing the bacteria under laboratory conditions, which can affect measuring adhesion. When the S-layer is dissolved with high concentration levels of substances that break down hydrogen bonds the S-layers have a survival time of about 20 minutes with each generation. L. brevis contains approximately two promoters within this area, meaning that there is significant transcription of the S-layer by high levels of transcribing of the sIpA gene. SipA is a gene that has been found to aid in the coding for the production of murin (peptidoglycan) within the bacteria. The purpose of transcription is to copy DNA into a mRNA, which is used to create proteins. The promoter is used during transcription to identify the appropriate location to begin transcribing. Within probiotics it is actually the S-layer that attaches to the cellular wall of the gastrointestinal tract.

Probiotics Ingestion of probiotics has been shown to improve human immune function, and L. brevis has been patented several times. L. brevis has been shown to survive in the gastrointestinal tract in humans and can therefore be used as a probiotic. Currently the bacterium does not have the ability to convert milk to yogurt however, they are appropriate to be used as an alternative to other probiotics in yogurts. Within the geriatric population use of the bacteria in milk has been shown to increase cellular immunity. Dietary probiotic supplementation enhances natural killer cell activity in the elderly (an investigation of age-related immunological changes). L. brevis is considered appropriate for probiotic use because there is significant growth at pH 4–5, particularly pH=5 is normally the appropriate range for milk and yogurts.

Biotherapies

There are significant vaginal bacteria that are found within the vagina and L. brevis is included in this microbiome. The bacteria collaborate on protecting the vagina and vaginal maintenance. Women of childbearing ages have a significant amount of L. brevis and this is normally found in a healthy vagina. For some illnesses or disruptions of the vagina, this bacteria can be used in aiding to restore the microbiome. Most lactobacilli have been found useful in preventing urinary tract infections. The efficiency in which a bacterium can defend the body is:

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Illustrations

Worked examples

Example 1 — a first encounter with Levilactobacillus brevis

Start with the simplest possible case. Write down what Levilactobacillus brevis 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 Levilactobacillus brevis 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 Levilactobacillus brevis 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 Levilactobacillus brevis

In research: Levilactobacillus brevis 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 Levilactobacillus brevis 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: Levilactobacillus brevis is common in secondary-school and first-year university syllabi. It links to neighbouring topics Dietary supplements, Food microbiology, Lactobacillaceae, so understanding it makes those chapters shorter.
In everyday life: Look for Levilactobacillus brevis 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 Levilactobacillus brevis in 20 minutes

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

Frequently asked questions

What is Levilactobacillus brevis in simple terms?

Why does Levilactobacillus brevis 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 Levilactobacillus brevis?

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 Levilactobacillus brevis.