Escherichia coli, often referred to as E. coli, is a versatile and intriguing bacterium that inhabits the human gut and plays a vital role in various aspects of our lives.
While it’s commonly associated with foodborne illnesses, there’s much more to E. coli than meets the eye.
In this article, we’ll explore 15 fascinating facts about E. coli, shedding light on its biology, its impact on health, and its importance in scientific research.
What is E. coli?
Escherichia coli (E. coli) are rod-shaped Gram-negative facultatively anaerobic bacteria belonging to the Enterobacteriaceae family.
They were first isolated from infant stool and characterized by Theodor Escherich in 1885 (Escobar-Paramo et al., 2003).
Escherichia coli, commonly known as E. coli, is a remarkable bacterium that dwells in the human gut and holds a pivotal role in various aspects of our lives.
Often associated with foodborne illnesses, E. coli is a microbe of significant scientific and practical interest.
E. coli is far more than a mere troublemaker; it is an integral part of the complex ecosystem that constitutes the human gut microbiome.
While some strains of E. coli can indeed cause health problems, many are benign and even beneficial, actively contributing to our overall well-being.
To appreciate the full spectrum of E. coli’s influence, we will explore various facets of this bacterium’s existence, from its biological functions to its historical significance and its applications in modern science and biotechnology.
15 Facts about Escherichia coli
- Escherichia coli (E. coli) is a gram-negative, facultative anaerobic, rod-shaped bacterium that is commonly found in the intestines of humans and animals.
- Most strains of E. coli are harmless and an important part of a healthy intestinal tract.
- E. coli is the best or most-studied free-living organism and has a record of 11 prestigious Nobel prizes associated with it.
- More than 700 serotypes of E. coli have been identified.
- E. coli can cause infection by producing Shiga toxins. The severity of the illness depends on the type of E. coli.
- E. coli is remarkably dangerous due to its very low infectious dose and its ability to survive in various conditions.
- E. coli can grow with or without oxygen, making it a versatile bacterium.
- The best-known and most notorious type of E. coli is E. coli O157:H7.
- Besides causing infections, E. coli can also be used to make useful substances like human insulin, human growth factor, taxol, and epidermal growth factor.
- Some strains of E. coli, such as Shiga toxin-producing E. coli (STEC), can cause severe foodborne diseases.
- E. coli can be transmitted to humans primarily through the consumption of contaminated foods, such as raw or undercooked ground meat products, raw milk, and contaminated raw vegetables and sprouts.
- E. coli O157:H7 is the most commonly found STEC strain in the United States and is often associated with severe symptoms.
- Symptoms of E. coli infections can include stomach cramps, diarrhea, vomiting, and in severe cases, life-threatening complications.
- E. coli infections can occur in people of all ages, but young children and the elderly are more likely to develop severe symptoms.
- Good hygiene practices, such as regular handwashing and proper food handling and preparation, can help reduce the risk of E. coli infections.
- Escherichia coli were named after Theodor Escherich, a German-Austrian pediatrician. Escherich first isolated a variety of bacteria from infant fecal samples by using his own anaerobic culture methods and Hans Christian Gram’s new staining technique (Escherich, 1988).
- After discovering E. coli in 1884, Escherich originally named the common colon bacillus, Bacterium coli commune.
- Later, in 1919, the bacterium was renamed after its discoverer by Castellani and Chalmers and became Escherichia coli. However, the name was not officially recognized until 1958.
Types of E.coli
There are hundreds of known E. coli strains. Notably, certain E.coli mediates various diseases, including intestinal and extraintestinal disorders in humans and animals worldwide.
Nine pathovars have been described for E. coli strains isolated from humans, causing diarrhealic and extraintestinal diseases (Nash et al., 2010).
Of these, seven pathotypes have been described as enteric pathogenic E. coli, including:
- Enteropathogenic E. coli(EPEC)
- Enterohaemorrhagic E. coli(EHEC)
- Enterotoxigenic E. coli (ETEC)
- Enteroinvasive E. coli (EIEC)
- Enteroaggregative E. coli (EAEC)
- Diffusely adherent E. coli (DAEC) and a new pathotype,
- Adherent-Invasive E. coli (AIEC), causes mostly diarrhea and intestinal disorders. (Donnenberg, 2013).
Many of these pathotypes constitute public health concerns as foodborne pathogens and cause several fatal outbreaks in developing and developed countries.
However, the EHEC (STEC) pathotype has been implicated in extraintestinal diseases such as Hemolytic Uremic Syndrome (HUS) (Donnenberg, (2013).
The STEC serotype, E. coli O157:H7 is the most widely recognized serotype due to the severity of the foodborne illness it causes (CDC 2015a).
In addition to E. coli O157:H7, other STEC E. coli serotypes have been shown to produce these toxins and cause foodborne illness.
The US Food and Drug Administration (FDA) has identified six serogroups, known as the “big six”. They are:
- E. coli O26,
- E. coli O45,
- E. coli O103,
- E. coli O111,
- E. coli O121, and
- E. coli O145. (FDA 2015)
These six serovars are the most commonly identified types of non-O157 E. coli serotypes found in foods and cause approximately 169,600 cases of foodborne illness in the US each year (CDC, 2016a).
These pathogenic strains have been designated as Shiga toxin-producing E. coli (STEC) in recognition of the similarities between the toxins produced by E. coli and Shigella dysenteriae (Murray et al. 2007).
Such potent toxins can cause severe damage to the intestinal lining, even in healthy individuals.
Even though the pathogenic members get more attention due to their virulence factors, it has to be pointed out that most strains of E. coli are indeed commensal. As a commensal bacterium.
E. coli is among the first colonizing bacteria of the gut after birth. It is a highly successful competitor in the human gut and is the most abundant facultative anaerobe of the human intestinal microbiota (Kaper, 2004).
After E. coli colonization, usually, the host and E. coli coexist in mutual benefit for decades (Kaper, 2004). While E. coli gets “food and shelter,” the host benefits from the E. coli vitamin K production and the “colonization resistance” E. coli offer.
Colonization resistance is the phenomenon of protection against colonization, by pathogenic bacteria, including against pathogenic E. coli (Stecher and Hardt, 2011).
Characteristics of E. coli
- Generally, E. coli can survive at both low and high temperatures ranging from 7°C (44.6°F) to 50°C (122°F). They can also survive under acidic conditions (at pH levels around 4.4), making them able to survive in mildly acidic food (WHO, 2018).
- E. coli is a Gram-negative rod-shaped bacterium. They are facultative anaerobes that are non-sporulating, nonmotile or motile (by peritrichous flagella), and chemoorganotrophic. They are known to produce acid from glucose, are catalase positive, oxidase negative, and mesophilic (Madigan et al.,2015).
- Although E. coli lacks many interesting features appreciated in biotechnology, such as growing at extreme temperatures or pH and the capacity to degrade toxic compounds, pollutants, or difficult-to-degrade polymers, it is much used in the industry because of its desirable traits, such as its fast growth rate in chemically defined media, and extensive molecular tools available for different purposes.
- All these make it an important model organism, which is why it is referred to as the “workhorse” of molecular biology (Vargas-Maya and Franco, 2017).
E. coli and Environment Survival
- To survive in varied environments, E. coli requires the ability to adapt to variations or extreme changes in temperature, pH, and osmolarity conditions commonly encountered in nature.
- E. coli can survive and persist in numerous environments such as soil, water, and food as well as in animal reservoirs.
- E. coli O157:H7 has been shown to survive for a year in manure-treated soil and for 21 months in raw manure that had not been composted (Jiang et al., 2002).
- These environmental adaptations play an important role in the ability of E.coli to persist in the environment and in its dissemination on farms and from one organism to another.
- E. coli survive when released into the environment and can spread to new hosts making it an important component of the biosphere (van Elsas, 2011).
Sources and Transmission of E.coli
Most available information on E.coli relates to the STEC stereotype – O157:H7 since it is easily differentiated biochemically from other E. coli strains.
E. coli reservoir of this pathogen appears to be mainly cattle. In addition, other ruminants such as sheep, goats, and deer are considered significant reservoirs, while other mammals (such as pigs, horses, rabbits, dogs, and cats) and birds (such as chickens and turkeys) have been found infected (WHO, 2018).
E. coli O157:H7 is transmitted to humans primarily through: other Interesting Facts about Escherichia coli are;
- consumption of contaminated foods,
- such as raw or undercooked meat and products;
- unpasteurized milk, ciders, and juices;
- consumption of contaminated fruits and vegetables;
- swallowing contaminated water and
- person-to-person contact. This is also an important mode of transmission through the oral-fecal route.
Who’s at Risk of E. coli Infection?
Certain groups of people are at a higher risk of developing severe illness from an Escherichia coli (E. coli) infection. These include:
- E. coli infections can be serious for healthy people of any age, but it is more likely to cause severe illness in the very young (those under age five).
- Workers in certain industries also have a higher risk of infection; those working in slaughterhouses, farms, hospitals, nursing homes, nursery schools, and food preparation locations are more susceptible to infection than the rest of the population (Keene, et al., 1994)
- Adults aged 65 and older have an increased chance of developing severe illness from E. coli infections.
- Individuals with weakened immune systems: People with weakened immune systems, such as those with chronic illnesses or taking immunosuppressive medications, are more vulnerable to severe complications from E. coli infections.
- Pregnant individuals: Pregnant people are at a slightly higher risk of developing severe illness from E. coli infections, although the risk is still relatively low.
- Travelers to certain countries: Travelers to regions with poor sanitation and limited access to clean water are at a higher risk of contracting E. coli infections. It is important to follow food and water safety precautions while traveling.
What Next?
E. coli’s significance extends beyond the laboratory, as it serves as an indicator of potential food contamination, emphasizing the importance of food safety measures.
Yet, it’s also a cause for concern due to its association with antibiotic resistance, underscoring the critical need for responsible antibiotic use in medicine and agriculture.
Certain pathogenic strains, particularly Shiga toxin-producing E. coli, have the potential to cause severe foodborne illnesses, reminding us of the importance of safe food handling practices.
On the flip side, E. coli’s adaptability and versatility have made it a valuable asset in biotechnology, contributing to the production of various beneficial substances and even playing a role in environmental cleanup efforts.