Photoblog: Introduction of Escherichia Coli

There is a new strain outbreak named Escherichia coli O104:H4 strain (ehec: Entero hemorrhagic Escherichia coli). But what is this bacteria and how does it cause diseases? How is a new strain formed?  Do i have this bacteria in me? If yes than how would i know? What should i do if i have it?



What is a Bacteria?
Below is a diagram of a bacteria. A bacteria is a prokaryotic organism i.e., made up of only one cell.

A typical prokaryotic Cell

This is how its cytoplasm look like:

Schematic inventory of the contents of the cytoplasm model. RNA is shown as green and yellow

It is not necessary for every bacteria to look like a rod as above. There are numerous shapes of bacteria. Escherichia Coli is rod shaped though.

Different Shapes of Bacteria

How does Escherchia Coli look like in Electron Microscope?

Escherichia coli O157:H7, cell with flagella, transmission electron microscopy

Electron micrograph of a cluster of E. coli bacteria. Each individual bacterium is oblong shape. Magnification: 10000x

This is how a single Escherichia Coli may move:

How do they grow?

Coloured Scanning Electron Microscope Picture with E.coli grown in culture

If you look carefully on the above photo than you will observe that some of them are dividing and some have divided while some are not dividing. Look below at the same photo but in black and white:

Scanning Electron Microscope Picture with E.coli grown in culture

Mechanism by which they reproduce:

Many types of bacteria including E. Coli divide by Binary Fission

Binary Fission: It is the process in which two cells form from one cell as shown above.

This highly magnified scanning electron micrographic view of a dividing Escherichia coli bacteria, clearly
displaying the point at which the bacteria’s cell wall was dividing; Magnification 21674x.

Here is something to understand how fast the above process takes place:

The average growth rate of all the cells corresponds to a doubling time of 28.2+/−0.1 min.

Here is another animation about the growth of there colony:

E. Coli colony is growing slowly

What will happen if this bacteria gets into you?
Nothing! The bacteria is already in your gut, living there in harmony with your body alongwith his/her brothers and sisters as well as anaerobes.

Than why does it cause disease?

Certain pathogenic strains of E. Coli causes disease by themselves or when when they outnumber your immune system

What is a strain?
Escherichia Coli has numerous parts and there are variations in these parts which give them different names or strains.

Parts of E. Coli which are basis of strain names:

• O Antigen: Present on the cell wall
• H Antigen: Present on Flagella
• K Antigen: Present on its capsule

So names of E. Coli are like O110:H7:K50 because there are approximately 150 variations of O, 50 variations of H and 90 variations of K antigen are found so far. Previously it was O157:H7 and now its O104:H4 causing problems for people.

Lets look at the different pathogenic parts of E. Coli:

Flagellum:

It rotates like a propeller when the bacterium swims.

The bacterial movement can be divided in 2 kinds:

• run, resulting from a counterclockwise rotation of the flagellum
• tumbling, from a clockwise rotation of the flagellum.

Pilli:
While in Gut these attach to gut wall from inside and release substances called enterotoxins (enteric means gut), which order the cells to pour electrolytes and water into gut leading to diarohea:

The long, sticky filaments covering E. coli bacteria uncoil under force, apparently improving the binding of the terminal adhesive unit in the presence of forces generated by fluid flow

 Lets take a look at one deadly enterotoxin which produces bloody diarrhea, it is called Shiga Toxin

Ribbon diagram of Shiga toxin type 2 (Stx2) from Escherichia coli O157:H7

Crystal structure of a mutated Shiga-like Toxin STx1 B subunit from Escherichia coli

Pathway for Causing Diarrhoea, can you see the verotoxin (shiga toxin) produced?

Capsule and Cell Wall:
These are the parts that when in blood lead to high fever and need immediate hospitalization.

Symptoms:
If a pathogenic (Disease causing) bacteria gets into gut you get:

• Watery Bloody Diarrhoea. Like this poor child:

Escherichia coli in FA stained section of intestine from an 8-month old child suffering from chronic diarrhea

• If the pathogenic organism enters into Blood:

• High Grade Fever with chills
• Low Blood Pressure
• Bleeding from other orifices and dark violet patches on skin seen in Disseminated intravascular coagulation

• If the organism enters into Brain:

• Meningitis. See this:

Escherichia coli in spinal or brain fluid. FA stain (digitally colorized).

• If the organism enters into Urinary tract:

• Pain on micturition 
• Urgency of micturition 

• In severe cases 

• severe flank pain
• fever with chills and above symptoms

Look at this:

Escherichia coli: Gram negative rod off a culture plate from a patient with Urinary Tract Infection

Growing E. Coli in Culture mediums on growth plates:
Along with ways like Electron microscopy of the specimen and gram staining them there are other ways to find them like the growth plate. In which growth medium like blood or boiled blood is placed and small quantity of specimen is poured into it and it is allowed to grow:

Pink Colony on MacConkey's agar

What is the treatment?
It is said that prevention is better than cure. Anyway if you think that you have it than you need to go to your Doctor and stick to his advice.

An E. Coli Cucumber!

Above Images have been taken from following sources: (not in order)

Wikimedia Commons

CDC

Flickr

PLoS

NIAID

These Images are either in Public Domain or there usage has been granted under one of the Creative Commons License types.

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