Appearance: E. coli is a rod-shaped bacterium, measuring approximately 0.5 μm in width by 2 μm in length (4). The bacterium has several fimbriae (3), which is one of its primary mechanisms of virulence because these help the bacterium attach much better to its host (5). Some strains are piliated. E. coli has only one circular chromosome (3).
Habitat: E. coli normally lives in the intestines of healthy animals and people (6). The GI tract is typically populated with E. coli within hours to days after birth (7). E. coli can also be found outside the GI tract, typically in feces, but it has also been found on the edge of hot springs (3).
Ecosystem: E. coli can be found wherever there are humans, warm-blooded animals, or surface water: ponds/lakes, wetlands, streams/rivers, hot & dry desert, semi-arid desert, coastal desert, cold desert, tropical forest, temperate forest, boreal forest, savanna, temperate grassland, arctic tundra, alpine tundra
Geographic Range: There are a few strains of E. coli that are especially harmful (such as E. coli O157:H7), and they can be found nearly everywhere. One is at a much higher risk for contracting these strains in areas where:
• There is contaminated food. The most common/recent issues have been concerning ground beef, unpasteurized milk, produce, and in restaurants where servers and cooks have poor hygiene.
• There is contaminated water. Human and animal feces can contaminate surface water. While municipal water systems are typically treated for E. coli, some outbreaks have still been traced to these supplies. However, private wells are of greater concern. Some people have also been infected through swimming in lakes or pools contaminated with E. coli.
• Personal contact with an infected person. Family members of young children are especially likely to acquire E. coli. Outbreaks have also been documented amongst children who have visited petting zoos and animal barns at local fairs (6).
How does it acquire nutrients and energy?
E. coli is a facultative anaerobe, which means that it can produce ATP either through aerobic respiration (if oxygen is available) or by fermentation (if oxygen is not available) (8 Facultative anaerobic organism, 2012).
How does it get rid of waste?
How does it reproduce?
E. coli reproduces via binary fission (9). However, it can spread its DNA via bacterial conjugation, transformation, or transduction, which allows for genetic diversity. E. coli is incredibly versatile and can grow in media with glucose as its only organic constituent. Optimal growth occurs at 37°C (98.6°F – the average human body temperature), but some strains have been known to multiply in conditions as warm as 49°C (120.2°F) (2).
How does it respond to its environment?
Considering it is a unicellular organism, E. coli is able to respond to its environment in many ways. It can sense the presence or absence of certain chemicals/gasses and will swim towards or away from them. It can grow fimbriae that will attach it to a specific cell or receptor. Finally, it will sense what is available for metabolism and will only produce the necessary enzymes when it is required (2).
Fascinating Fact:
While we typically think of E. coli as harmful, it is one of the main bacteria in our GI tracts and can live there commensally unless it acquires genetic information that leads to virulence factors. In fact, E. coli can even be helpful. The strain Nissle 1917 (sometimes known as Mutaflor) is used as a probiotic agent in medicine used to treat some GI diseases such as inflammatory bowel syndrome (IBS) (2).
Current Scholarly Research:
Touchon, M., et al. (2009). Organised genome dynamics in the Escherichia coli species results in highly diverse adaptive paths. PLoS Genetics 5(1), 1-25.
Researchers sought to investigate the genomes of 20 strains of E. coli. They found that although there is a great deal of gene exchange through recombination, the genome is still highly organized. This adds to our knowledge concerning how E. coli evolves.
Barrick, J.E., Yu, D.S., Yoon, S.H., Jeong, H., Oh, T.K., Schneider, D., Lenski, R.E., Kim, J.F. (2009). Genome evolution and adaptation in along-term experiment with Escherichia coli. Nature, 461, 1243-1249.
Researchers sequenced genomes from 40,000 generations of a laboratory population of E. coli in order to study the relationship between the rates of genomic evolution and organismal adaptation. They found that rather than neutral mutations, there was a regular rate of beneficial substitutions, which can be counterintuitive when studying evolution. This adds to our knowledge concerning how E. coli evolves.
Keseler, I.M., et al. (2009). EcoCyc: A comprehensive view of Escherichia coli biology. Nucleic Acids Research, 37, D464-D470.
EcoCyc (http://EcoCyc.org) has been created by researchers as an encyclopedia of E. coli and includes information about the genome, metabolic network, and the regulatory network of E. coli. There are data sets available, a genome browser, and a way to build database inquiries. This database of information about E. coli can aide scientists and medical professionals in understanding how E. coli and humans interact.
Species in the News:
Harrington, R. (6 December 2011). Industry and governments blast US plans to ban non-O157 E. coli. Retrieved from FoodProductionDaily.com: http://www.foodproductiondaily.com/Quality-Safety/Industry-and-governments-blast-US-plans-to-ban-non-0157-E.coli
The U.S. Department of Agriculture’s (USDA) Food Safety Inspection Service (FSIS) announced that beginning March 5, 2012, it will begin testing meat for six strains of non-O157 E. coli. The American Meat Institute as well as the Australian and New Zealand governments have attacked this proposal and feel it is premature. They believe the USDA’s FSIS has large gaps in its data and so have requested that this plan be postponed until the policy’s possible impact can be studied further.
Casey, T. (29 November 2011). E. Coli bacteria: What doesn’t kill us, makes us biofuel. Retrieved from CleanTechnica.com: http://cleantechnica.com/2011/11/29/e-coli-bacteria-what-doesnt-kill-us-makes-us-biofuel/
The U.S. Department of Energy has altered a strain of E. coli to feed on switchgrass in order to create renewable gasoline, diesel, and jet biofuel. Scientists had to alter an enzyme in the bacteria and soften the switchgrass with molten salt.
The Associated Press. (16 November 2011). Raw milk recalled after children sickened by E. coli. Retrieved from Today Health: http://today.msnbc.msn.com/id/45326017/ns/today-today_health/t/raw-milk-recalled-after-children-sickened-e-coli/#.Tt6lXkoZCUc
The Organic Pastures Dairy Company in California was forced to recall its raw milk products after E. coli sent three children to the hospital. While lab samples from the dairy as well as samples of the milk consumed by the children did not detect strains of E. coli, the only common exposure between all the children was Organic Pastures raw milk products.
Why Should I Care?:
Because E. coli is so easily cultured and manipulated within a laboratory, it plays a large role in biotechnology. Cohen and Boyer used E. coli to create recombinant DNA, which is the foundation of biotechnology. One of the first applications of recombinant DNA was the manipulation of E. coli to produce insulin. Modified E. coli has been used in vaccines and bioremediation. Further, because E. coli can survive outside a host, it is a good indicator of fecal contamination in the water supply (2).
Commensalistic or Parasitic Relationship:
E. coli can be either commensalistic, such as living in human gastrointestinal tracts as normal flora, or parasitic, such as causing gastrointestinal distress, depending on the strain (2).
