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     Where can I find E. coli? 

      The primary habitat of Escherichia coli is in the gastrointestinal (GI) tract of humans and many of the warm blooded animals. 

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Human Gastroinestinal Tract

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      There are many bacteria that can be found in the human body, and most of them are strict anaerobes.  However, E. coli is the most abundant facultatively anaerobic microorganism that is found in the GI tract of humans and mammals.  The average human GI tract contains

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E. coli in the Intestine of a Human
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upwards of 1 kg (~2.21 lb) of bacteria, and approximately 0.1-1% of these are E. coli.  In fact, these bacteria appear in the body just a few hours after birth.  Don't let this scare you, because most of these E. coli bacteria are harmless opportunistic organisms.  The E. coli actually forms a mutualistic relationship with its host (see Interaction). The

bacteria normally adhere to the mucus or the epithelium on the wall of the intestines (which is critical, otherwise most E. coli will not grow in that particular area), and a single strain can last for months or years. 

      How does E. coli fit into its ecological nicheE. coli is one of the most studied and best understood organism, but the organism's niche and how it colonizes isn't very well understood.  Freter's Nutrient-Niche theory best describes E. coli's niche: The ecological niches of E. coli depend on the nutrient availability within the intestines of the host organism.  Since there are so many different nutrients that can be found within the intestines, it is said that they contain a balanced ecosystem because there are so many different nutrient-defined niches where the E. coli colonize.  This is dependent on the preferred nutrient for that particular population occupying the niche.

    It must also be taken into account the difference between the small and large intestine.  The velocities of movement of chyme is much higher in the small intestine than it is in the large intestine (also called the colon), so in order for E. coli to thrive in the small intestine it MUST be able to adhere to the wall of the small intestine or it will be swept away.  If the E. coli is unable to grow on the intestinal wall, it will be most likely to colonize in the colon.  Therefore, different regions in the GI tract represent different niches as well (niche specialization).

      E. coli can also be found oRetrieved from Microsoft ClipArtutside of the body in faecally-contaminated environments such as water or mud.

Interested in Learning more about some potential E. coli hosts???  Check out some other student's webpages:

1. Llama glama

2. Lemur catta

3. Bos taurus

4. Acinonyx jubatus

5. Ovis canadensis

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©April 2008