Escherichia coli is one of the most well-known microbes in the world and the species includes diverse strains of bacteria. Most of these strains are harmless and occur widely in nature as well as in the gastrointestinal tracts of humans and other vertebrates. They help synthesize vitamins K and B complex and also assist in food digestion and absorption. However, other strains cause infections that can lead to serious consequences.
E. coli is also used as a model organism in scientific research and is very important in the development of modern molecular biology. Its fast growth rates and genetic simplicity (E. coli has only 4,400 genes compared to ~25,000 genes in human cells) has led to its widespread use in laboratories. Colonies are easy to start and maintain, and are even used to sustain another model organism, the roundworm Caenorhabditis elegans. Major discoveries in our understanding of bacterial physiology and genetics, DNA replication, and genetic engineering have been enabled by E. coli.
The bacterium was discovered in 1885 by Theodor von Escherich, who named it Bacterium coli commune. "Coli" refers to the fact that Escherich found the organism in the colon and "bacterium" is a genus name no longer used. In 1919, the bacterium was renamed Escherichia coli to honor its discoverer, though this was not officially endorsed until 1958. The genus Escherichia has many other species that are found in the gastrointestinal tracts of vertebrates. The vast majority of bacteria do not have common names, but E. coli is so important to human health and scientific research that the term has become used as a common name as well.
The Man behind the Bacterium
Theodor Escherich (1857–1911) was a pioneering German pediatrician who worked to improve childcare by focusing on hygiene and nutrition. In 1884, while living in Munich, Escherich began research on the bacteria of infant intestinal tracts and how they change after birth and used these studies to investigate diseases in infants. He learned how to characterize and culture bacteria, conducting experiments in laboratories, institutes, and even dairy-industry facilities. He demonstrated that bacterial colonization in infants was attributable to their environment 3–24 hours after birth. It was also at this time that Escherich officially presented his work on Bacterium coli commune to the Society for Morphology and Physiology on July 14, 1885.
In 1890, Escherich was offered a position as a professor and director of a children’s hospital in Graz, Austria. He discovered that coliform bacteria are associated with intestinal infections in infants. He also noted that the Bacterium coli commune was frequently found in urine samples of young girls, which shed light on the significance of urinary tract infections. Escherich’s success in Graz led him to be nominated as Chair of Pediatrics at the University of Vienna and Director of the St. Anna Children’s Hospital of Vienna in 1902. While there, he modernized the hospital, and founded the Austrian Society for Children’s Research. Today he is remembered as a pioneer in pediatrics and the first pediatric infectious disease physician.
Did you know? Professor Richard Lenski, at Michigan State University, has been studying the genetic changes in twelve (originally) identical populations of E. coli since 1988. The experiment has now reached more than 65,000 generations, making it the longest running study in experimental evolution in the world. The goal is to study the dynamics of evolution, particularly the rate of evolutionary change.
E.coli and Disease
Some types of E. coli cause disease by making a "Shiga toxin." The bacteria that produce this are often referred to as STEC (Shiga toxin-producing Escherichia coli) and in North America the most common form that causes infections is E. coli O157:H7. While common symptoms are stomach cramps, diarrhea, and vomiting, more severe complications include hemolytic-uremic syndrome, a condition in which red blood cells are destroyed at an abnormal rate, leading to renal failure and death.
STEC live in the guts of ruminant animals, including cattle, goats, and sheep. Sources of illness inducing E. coli often come from contaminated, uncooked food such as raw beef, unpasteurized dairy products, and raw fruits and vegetables. Water can also be contaminated with E. coli. Working with and handling livestock, especially cattle, is an additional risk factor for contracting an E. coli related illness. E. coli has also been used to fight diseases as it can be altered genetically with relative ease. It has been used to make antibiotics, manufacture insulin, and treat cancer.
Did you know? While E. coli is one of the most commonly used bacteria in science, its function goes far beyond simple experimentation. Studies are being conducted to see if E. coli can be used to make a fossil fuel replacement. Ideally, the bacteria would produce fats similar to gasoline molecules.
Information on E. coli from the Centers for Disease Control and Prevention
An article on Richard Lenski’s experiment: “The man who bottled evolution”
An animation from the Howard Hughes Medical Institute on how an infectious strain of E. coli causes serious illness.
Slideshow Image Credits
Scanning electron micrograph of E. coli, National Institute of Allergy and Infectious Diseases (NIAID); Theodor Escherich, U.S National Library of Medicine (NIH). Public Domain; Colon diagram, Wikimedia Commons. CC BY; E.coli. Centers for Disease Control and Prevention. Public Domain