science

Segmented filamentous bacteria

Segmented filamentous bacteria 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 Segmented filamentous bacteria rather than just read about it. In short: Segmented filamentous bacteria (SFB) are members of the gut microbiota of mammals, fish, and birds, and have been shown to potently induce immune responses in mice. They have a distinct morphology and form their own clade within the Clostridiaceae.

Key takeaways

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

Reference excerpt

Segmented filamentous bacteria (SFB) are members of the gut microbiota of mammals, fish, and birds, and have been shown to potently induce immune responses in mice. They have a distinct morphology and form their own clade within the Clostridiaceae. The SFB genus is known as Anisomitus, for "uneven thread", with A. miae as the nomenclature type (seqco.de/r:zlg3gn05). Previously, the name Candidatus Savagella was proposed for this lineage after they had been referred to as Candidatus Arthromitus due to their morphological resemblance to bacterial filaments previously observed in the guts of insects by Joseph Leidy. Despite the fact that they have been widely referred to as segmented filamentous bacteria, this term is somewhat problematic as it does not allow one to distinguish between different bacterial species that colonize various hosts. In mice, these bacteria grow primarily in the terminal ileum in close proximity to the intestinal epithelium where they are thought to help induce T helper 17 cell responses. Mouse studies indicate SFB-induced Th17 cells can convert to Th1-like cells, enhancing anti-PD-1 tumor control against tumors sharing an SFB antigen. Intriguingly, Segmented Filamentous Bacteria were found to expand in AID-deficient mice, which lack the ability to mount an appropriate humoral immune response because of impaired somatic hypermutation; parabiotic experiments revealed the importance of IgA in eliminating Segmented Filamentous Bacteria. This goes hand in hand with an earlier study demonstrating the ability of monocolonization with Segmented Filamentous Bacteria to dramatically increase mucosal IgA levels. Segmented Filamentous Bacteria are species specific, and may be important to immune development.

See also List of bacteria genera List of bacterial orders

References

Gut Immune Maturation Depends on Colonization with a Host-Specific Microbiota (Cell Volume 149, Issue 7 2012 1578 – 1593)

Further reading At least 50 scholarly articles on the subject at Google scholar. Two review articles

Ivanov II; Littman DR (May 2010). "Segmented filamentous bacteria take the stage". Mucosal Immunol. 3 (3): 209–12. doi:10.1038/mi.2010.3. PMC 3010405. PMID 20147894.{{cite journal}}: CS1 maint: unflagged free DOI (link) Klaasen HL; Koopman JP; Poelma FG; Beynen AC (June 1992). "Intestinal, segmented, filamentous bacteria". FEMS Microbiol. Rev. 8 (3–4): 165–80. doi:10.1016/0378-1097(92)90801-t. PMID 1515159.

Worked examples

Example 1 — a first encounter with Segmented filamentous bacteria

Start with the simplest possible case. Write down what Segmented filamentous bacteria 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 Segmented filamentous bacteria 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 Segmented filamentous bacteria 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 Segmented filamentous bacteria

In research: Segmented filamentous bacteria 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 Segmented filamentous bacteria 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: Segmented filamentous bacteria is common in secondary-school and first-year university syllabi. It links to neighbouring topics Bacteria, Candidatus taxa, so understanding it makes those chapters shorter.
In everyday life: Look for Segmented filamentous bacteria 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.

Affiliate

Preply — study more efficiently by working with a personal tutor. 50% off.

How to study Segmented filamentous bacteria in 20 minutes

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

Frequently asked questions

What is Segmented filamentous bacteria in simple terms?

Why does Segmented filamentous bacteria 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 Segmented filamentous bacteria?

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 Segmented filamentous bacteria.