Expert: Christopher Rosch - 9/2/2004

Question
Hi Chris,

How are you doing? I just want to know the life cycle of e.coli? Do they die off by itself or can they lose out to other beneficial bacteria in terms of competition for nutrients?

Thanks

regards
simon

Answer
Hi Simon,

I'm not sure what you mean by life cycle. Usually, E.coli just stays in the large intestine. It is a perfectly normal part of the intestinal microflora and generally not harmful; it does little else than grow and divide. However, with the faeces some E.coli get into the wastewater and from there may pollute drinking water. But this generally is no problem as they barely reproduce in the water. E.coli is not well adapted to survive in nutrient poor water - just as you suspected. It grows best on simple sugars and amino acids which occur in extremely low concentrations in aquatic environments. Concerning its pathogenicity, E.coli needs no intermediate hosts to infect humans (like certain pathogens). It can cause blood poisoning when it enters the bloodstream, e.g. by skin lesions. But this happens rather by "accident" - E.coli prefers the intestine as its habitat.

Perhaps you find the following links useful:
http://www.ccme.ca/sourcetotap/ecoli.html
http://people.ku.edu/~jbrown/ecoli.html

Have a nice day,
Christopher