biology

Pathogenic Escherichia coli

Pathogenic Escherichia coli 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 Pathogenic Escherichia coli rather than just read about it. In short: Escherichia coli ( ESH-ə-RIK-ee-ə KOH-ly; commonly abbreviated E. coli) is a gram-negative, rod-shaped bacterium that is commonly found in the lower intestine of warm-blooded organisms (endotherms). Most E. coli strains are harmless, but pathogenic varieties cause serious food poisoning, septic shock, meningitis, or urinary tract infections in humans.

Key takeaways

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

Reference excerpt

Escherichia coli ( ESH-ə-RIK-ee-ə KOH-ly; commonly abbreviated E. coli) is a gram-negative, rod-shaped bacterium that is commonly found in the lower intestine of warm-blooded organisms (endotherms). Most E. coli strains are harmless, but pathogenic varieties cause serious food poisoning, septic shock, meningitis, or urinary tract infections in humans. Unlike normal flora E. coli, the pathogenic varieties produce toxins and other virulence factors that enable them to reside in parts of the body normally not inhabited by E. coli, and to damage host cells. These pathogenic traits are encoded by virulence genes carried only by the pathogens.

Introduction E. coli and related bacteria constitute about 0.1% of gut flora, and fecal–oral transmission is the major route through which pathogenic strains of the bacterium cause disease. Cells are able to survive outside the body for only a limited amount of time, which makes them ideal indicator organisms to test environmental samples for fecal contamination. The bacterium can also be grown easily and inexpensively in a laboratory setting, and has been intensively investigated for over 60 years. E. coli is the most widely studied prokaryotic model organism, and an important species in the fields of biotechnology and microbiology, where it has served as the host organism for the majority of work with recombinant DNA. German paediatrician and bacteriologist Theodor Escherich discovered E. coli in 1885, and it is now classified as part of the Gammaproteobacterial family Enterobacteriaceae.

Serotypes

Pathogenic E. coli strains can be categorized based on elements that can elicit an immune response in animals, namely:

O antigen: part of lipopolysaccharide layer K antigen: capsule H antigen: flagellin For example, E. coli strain EDL933 is of the O157:H7 group. Some, but not all, E. coli fimbrial antigens are also given names in the form of F followed by a number.

O antigen

The outer membrane of an E. coli cell contains millions of lipopolysaccharide (LPS) molecules, which consists of:

O antigen, a polymer of immunogenic repeating oligosaccharides (1–40 units) Core region of phosphorylated nonrepeating oligosaccharides Lipid A (endotoxin) The O antigen is used for serotyping E. coli and these O group designations go from O1 to O181, with the exception of some groups which have been historically removed, namely O31, O47, O67, O72, O93 (now K84), O94, and O122; groups 174 to 181 are provisional (O174=OX3 and O175=OX7) or are under investigation (176 to 181 are STEC/VTEC). Additionally subtypes exist for many O groups (e.g. O128ab and O128ac). Antibodies towards several O antigens cross-react with other O antigens and partially to K antigens not only from E. coli, but also from other Escherichia species and Enterobacteriaceae species. The O antigen is encoded by the rfb gene cluster. rol (cld) gene encodes the regulator of lipopolysaccharide O-chain length.

K antigen

The acidic capsular polysaccharide (CPS) is a thick, mucous-like, layer of polysaccharide that surrounds some pathogen E. coli. There are two separate groups of K-antigen groups, named group I and group II (while a small in-between subset (K3, K10, and K54/K96) has been classified as group III). The former (I) consist of 100 kDa (large) capsular polysaccharides, while the latter (II), associated with extraintestinal diseases, are under 50 kDa in size. Group I K antigens are only found with certain O-antigens (O8, O9, O20, and O101 groups), they are further subdivided on the basis of absence (IA, similar to that of Klebsiella species in structure) or presence (IB) of amino sugars and some group I K-antigens are attached to the lipid A-core of the lipopolysaccharide (KLPS), in a similar way to O antigens (and being structurally identical to O antigens in some instances are only considered as K antigens when co-expressed with another authentic O antigen). Group II K antigens closely resemble those in gram-positive bacteria and greatly differ in composition and are further subdivided according to their acidic components, generally 20–50% of the CPS chains are bound to phospholipids. In total there are 60 different K antigens that have been recognized (K1, K2a/ac, K3, K4, K5, K6, K7 (=K56), K8, K9 (=O104), K10, K11, K12 (K82), K13(=K20 and =K23), K14, K15, K16, K18a, K18ab (=K22), K19, K24, K26, K27, K28, K29, K30, K31, K34, K37, K39, K40, K41, K42, K43, K44, K45, K46, K47, K49 (O46), K50, K51, K52, K53, K54 (=K96), K55, K74, K84, K85ab/ac (=O141), K87 (=O32), K92, K93, K95, K97, K98, K100, K101, K102, K103, KX104, KX105, and KX106).

H antigen

The H antigen is a major component of flagella, involved in E. coli movement. It is generally encoded by the fliC gene There are 53 identified H antigens, numbered from H1 to H56 (H13 and H22 were not E. coli antigens but from Citrobacter freundii, and H50 was found to be the same as H10).

Role in disease In humans and in domestic animals, virulent strains of E. coli can cause various diseases. In humans: gastroenteritis, urinary tract infection, and neonatal meningitis. In rarer cases, virulent strains are also responsible for hemolytic-uremic syndrome, peritonitis, mastitis, gram-negative pneumonia and sepsis.

Gastrointestinal infection

… excerpt ends here. Continue reading the full article.

Illustrations

Worked examples

Example 1 — a first encounter with Pathogenic Escherichia coli

Start with the simplest possible case. Write down what Pathogenic Escherichia coli 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 Pathogenic Escherichia coli 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 Pathogenic Escherichia coli 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 Pathogenic Escherichia coli

In research: Pathogenic Escherichia coli 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 Pathogenic Escherichia coli 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: Pathogenic Escherichia coli is common in secondary-school and first-year university syllabi. It links to neighbouring topics Bird diseases, Escherichia coli, Infraspecific bacteria taxa, so understanding it makes those chapters shorter.
In everyday life: Look for Pathogenic Escherichia coli 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 Pathogenic Escherichia coli in 20 minutes

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

Frequently asked questions

What is Pathogenic Escherichia coli in simple terms?

Why does Pathogenic Escherichia coli 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 Pathogenic Escherichia coli?

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 Pathogenic Escherichia coli.