Escherichia coli

Escherichia coli, often called E. coli, is a type of tiny living thing called a bacterium. It is commonly found in the intestines of warm-blooded animals, including humans. Most kinds of E. coli are harmless and can even be helpful. For example, some E. coli strains help make vitamin K₂ and stop harmful bacteria from growing in our guts. This is a good partnership where both the bacteria and humans benefit.

However, some types of E. coli can make people sick. They can cause food poisoning, often spreading through food that has not been handled or cooked properly. Scientists study E. coli a lot because it is easy to grow in labs and learn from. It has been very important in biotechnology and microbiology, helping scientists understand how living things work and make new medicines and technologies. E. coli can reproduce very quickly, sometimes in just 20 minutes, under the right conditions.

Biology and biochemistry

E. coli is a type of bacteria with a thin outer layer and rod-like shape. It usually lives in the intestines of warm-blooded animals, including humans, where most types are harmless or even helpful.

E. coli can survive with or without oxygen and can use many different food sources. It changes its way of getting energy depending on what is available, such as using glucose or other sugars. Scientists study E. coli in labs because it grows easily under controlled conditions.

The bacteria reproduce quickly, especially when there is plenty of food. They can copy their DNA and split into two cells many times in a short period. Even while splitting, the bacteria can keep copying their DNA, leading to complex patterns of growth.

Diversity

Escherichia coli includes many different types of bacteria that can vary greatly in their traits and behaviors. Only about 20% of the genes in one E. coli strain are shared with all other strains, making it one of the most diverse bacterial species. Some strains, like those in the genus Shigella, might actually belong to E. coli based on their genetic makeup.

A strain is a group within the species that has unique features. These differences can affect how the bacteria live or cause disease. For example, some strains can make people sick, while others are used in labs for research. Scientists can often tell where contamination in water comes from by looking at which E. coli strains are present.

Serotypes

Main article: Pathogenic Escherichia coli § Serotypes

E. coli strains can also be grouped by their surface proteins, called serotypes. This helps scientists study them, though not all strains have these proteins.

Genome plasticity and evolution

Like all living things, E. coli changes over time through natural processes. Some strains can develop harmful traits, often causing diarrhea in people. While this is usually not serious for healthy adults, it can be very dangerous for young children in places without good healthcare.

In labs, scientists have watched E. coli change over many generations. For example, some strains learned to use a new food source, showing how bacteria can adapt.

Neotype strain

E. coli is the main species in its genus. Because the original sample used to describe it is lost, scientists chose a new representative strain. Different strains are used in research, each with its own features.

Phylogeny of E. coli strains

Scientists have studied many E. coli strains and grouped them based on their evolutionary history. This helps understand how they relate to each other, even though their ability to cause disease does not always match how closely related they are.

Genomics

In 1997, scientists finished mapping the full DNA blueprint of a special kind of E. coli bacteria. This DNA is a single, circular piece about 4.6 million building blocks long. It holds many instructions for making proteins, as well as pieces for building and reading RNA. Even after many years of study, researchers found new genes they didn’t know about before.

Scientists have now mapped the DNA of many different E. coli types. While they share some basic instructions, most of their DNA differs between types. Each type carries between 4,000 and 5,500 genes, but when you look at all types together, there are over 16,000 different genes. Many of these genes came from other bacteria through a process called horizontal gene transfer.

Gene nomenclature

See also: Gene nomenclature § Bacterial genetic nomenclature

Genes in E. coli are named following special rules. The names are three letters that show what the gene does or how it changes when broken. These names are written in italics. If more than one gene has the same three letters, a big letter is added after to tell them apart. For example, a gene named recA is linked to homologous recombination and the letter A. Related genes might be named recB, recC, and recD.

When scientists mapped out the genes in a special kind of E. coli, they gave each gene a number starting with “b”, like b2819, which is the same as recD. Another group in Japan used numbers starting with “JW”, such as JW2787, which is also recD. Different databases may use their own numbers, like EG10826 for recD. You can find full lists of these genes in databases such as EcoGene or Uniprot.

Proteomics

Proteome

Scientists have studied the proteins made by E. coli. By 2006, they had found evidence of 1,627 proteins out of the 4,288 that the bacteria can make. More recent research in 2020 found 2,586 different proteins.

Post-translational modifications (PTMs)

Some proteins in E. coli change after they are made. For example, researchers found that many proteins have extra pieces added to them, especially at certain spots like serine, histidine, threonine, and tyrosine.

Interactome

Researchers have looked at how the proteins in E. coli work together. They used special methods to find out which proteins connect with each other. In one study, they found many connections between different proteins, helping us understand how these tiny living things function.

Normal microbiota

E. coli is a type of bacteria found in the digestive systems of warm-blooded animals, like humans. It is part of a group called coliforms. This bacteria usually enters a baby’s gastrointestinal tract within 40 hours after birth, often through food, water, or from people caring for the baby. Once inside, it sticks to the mucus in the large intestine. Most of the time, E. coli is harmless and can even be helpful.

Therapeutic use

E. coli is also used in laboratories because it can grow quickly and cheaply. Scientists use it to make important proteins for medicines. Some special kinds of E. coli, like strain Nissle 1917 and E. coli O83:K24:H31, are used to help people with certain stomach problems, such as inflammatory bowel disease. These helpful bacteria can prevent harmful germs, like Salmonella, from growing.

Role in disease

Main article: Pathogenic Escherichia coli

Most strains of E. coli do not cause illness. They live naturally in our guts. However, some stronger strains can make people very sick. These strains can cause stomach pain, diarrhea, and infections in the urinary tract. Very young children are more likely to get very sick from these bacteria.

Some special kinds of E. coli, like O157:H7, can make a harmful substance that damages the gut and can even affect the kidneys. This can be very dangerous, especially for young children and older adults.

One common type, called ETEC, often causes traveler's diarrhea. It spreads through dirty food or water and can make people very sick, especially children in places where clean water is not always available.

In 2011, a serious outbreak of a different E. coli strain happened in Germany. This strain spread to many other countries and caused many people to get very sick.

To help prevent E. coli infections, it is important to wash hands well, keep food clean, cook meat thoroughly, and avoid drinking raw or unpasteurized liquids like certain juices or milk. These steps can help keep people safe from getting sick.

Model organism in life science research

Because it has been grown in labs for a long time and is easy to work with, E. coli is very important in modern biology and making things in factories. Important scientists used E. coli to help start the field of biotechnology.

Scientists can put new genes into E. coli to make it produce useful proteins, like human insulin, in large amounts. E. coli is also used to develop vaccines, clean up pollution, make fuels, and create special enzymes. Some special types of E. coli, like K-12 and JM109, are used in labs for studying and making new things.

E. coli is often used in labs to study tiny living things. Lab versions of E. coli are not the same as the ones in our bodies and cannot live there. Scientists use E. coli to test new ways to clean and treat water. It was also used to discover how bacteria can share DNA with each other. E. coli was one of the first tiny creatures to have its full set of instructions (genome) read.

A special version called MDS42 was made by removing some parts of its instructions to make lab work easier. Scientists also use E. coli to study how tiny creatures change and adapt in different conditions.

Uses in biological computing

See also: Biological computing

Since 1961, scientists have thought about using the genes of tiny living things to do math and solve problems. One type of these tiny living things is called E. coli. Researchers have found ways to use the way E. coli works to create simple computers. They can control how these tiny living things make proteins, which are important pieces that help them live.

Scientists have even tried to teach E. coli to solve tricky math puzzles and to act like a screen that shows pictures. In 2017, a group of scientists showed that E. coli could be used to store information, like pictures and videos, inside its DNA. Later, they also made E. coli solve small maze problems to learn more about how groups of cells can work together.

History

In 1885, a doctor named Theodor Escherich found this tiny living thing in the waste of healthy people. He named it Bacterium coli commune because it lives in the colon part of the body. Over time, scientists changed its name a few times before settling on Escherichia coli, naming it after its discoverer.

There have been some sicknesses caused by certain kinds of E. coli, such as one in Scotland in 1996 and another in Germany in 2011. More recently, in 2024, an outbreak in the U.S. was linked to organic carrots and made many people sick.

Uses

E. coli has many useful purposes. Scientists use it to make important medicines, like a special human growth hormone that helps people stay healthy. It can also help create useful fuels, such as synthetic propane, which can be used in vehicles and heating.