E. coli is a bacterium found in large quantities in the digestive system of humans, cows and other mammals. In several countries, the bacterium has been responsible for a large number of outbreaks of contamination. In most cases, the disease causes nonlethal problems in the stomach. However, enterohemorrhagic E. coli (ECEH) causes more severe symptoms, ranging from bloody diarrhea to haemolytic uremic syndrome.
In any living organism genes are not active all the time, gene activation results from the response the organism needs for a given time or situation. In the case of E. coli, only 60% of its genes are active at the same time and all the time, the other 40% are waiting for the moment when some protein will need to be coded. Since bacteria have only one cell, gene activation is done very quickly to ensure survival.
