E-Coli:  Friend of Foe
Probably one of the many gross images I have had the privilege of seeing was that of a cat dish that was filled with food a week earlier and not cleaned out.  A week later, the cat dish was moving... with what?... not the bacteria E-coli pictured on the right, but instead with maggots that look pretty much like the E-coli only much bigger.  The image of things growing in our food or in our guts is not always the most pleasing picture.  However without them, our food in part would not be digested, waste products not recycled.  So the question is when and how is E-Coli toxic? 

The Life Cycle of E-coli... Most of the time... Good Guys

A Bad Strain:  E-Coli O157:H7