The Bacterium Itself
E. coli is classed as an anaerobic, Gram-negative bacterium of the Enterobacteriaceae family, which also includes familiar bacteria such as Salmonella and Shigella. The bacterium is rod-shaped, generally about two microns in length, with some strains possessing flagella. On both a genotypic and phenotypic level, E. coli displays diverse forms. It can dwell in a wide variety of substrates, and thrives in multiple environments. The E. coli genome has been researched extensively, and a complete DNA sequence was published in 1997. However, its use as a model organism in laboratories goes back much further. Due to the ease of genetic manipulation, the bacterium is often used in case studies and experiments. Indeed, a strong difference has developed between laboratory-type E. coli and wild type, analogous to the difference between the white rats that dwell in labs and the brown ones that live in basements and barns. “Domesticated” E. coli has been used in the study of long-term evolutionary shifts, bacteriophage genetics, and a host of other genetic/evolutionary experiments. There has been some suggestion that, in one evolutionary experiment, speciation in the lab occurred for the first time in the history of experimental biology. Some researchers have even used E. coli in mathematical modeling and in micro-scale studies of biogeography, as well as in genetic engineering. The bacterium is generally found in the gastrointestinal tract of warm-blooded organisms, although it can survive in fields when feces is used in the production of manure. Cattle, humans, horses, goats, swine, and sheep all possess E. coli in their bodies. Different environments are more accommodating to different strains of the bacterium, some of which are harmless, and others of which lead to diarrhea and fever (more on that later). In the human gut, E. coli is present as a commensal organism, neither helping nor hurting the host human. The bacterium generally colonizes the gastrointestinal tract of infants within 40 hours of birth. For those with chronic bowel conditions, such as Crohn's disease or ulcerative colitis, E. coli counts are generally higher.Infection and Disease
The bacterium is most familiar to most people as an agent in food poisoning. Numerous virotypes of E. coli exist, each producing different symptoms and dwelling in different environments; they include enterotoxigenic, enteropathogenic, enteroinvasive, enterohemorrhagic, and entroaggregative types. All of these are generally transmitted fecally. E. coli-caused food poisoning generally results from fecal-to-oral transmission through food. Some of the common disease vectors include food prepared in an unhygienic environment, unpasteurized dairy, poorly butchered or cooked meat (especially ground beef), and fruits and vegetables fertilized with manure. Even if one eats clean food, contact with farm animals can also lead to infection. Hand-washing and safe food handling are the best ways to prevent this route of infection. Other infections can also be caused by E. coli. One of the most common is urinary tract infection (UTI), with 90% of UTI cases caused by E. coli. This almost entirely affects women, with 14 women acquiring a urinary tract infection per every one man. Far less commonly, E. coli can also cause meningitis in newborns if the mother's vagina is infected. The bacterium can also cause infections internally; if the gastrointestinal tract is perforated, feces can enter the bloodstream, causing peritonitis. In case of E. coli infection, antibiotics have been the traditional treatment. However, antibiotic-resistant strains have evolved, and there is some fear that resistant E. coli bacteria have the potential to become a “superbug” in coming decades. At the present time, penicillin is on its way out as an effective treatment for E. coli infection. In the former Eastern bloc, in Poland and Georgia, research has been maintained for decades into the treatment of infections with bacteriophages, and there is a great deal of hope in this regard. There has also been fruitful research into the possibility of an E. coli vaccine over the past few years.Further Reading
We've included scientific resources, including those covering the infections caused by the bacterium, the biology of the bacterium, and some of the research being conducted using E. coli.