Have you ever had food poisoning?
If yes, there is a good chance that you came in contact with
Campylobacter jejuni, the worldwide leading cause of
food-borne bacterial infection. 
The name Campylobacter ("curved rod" in Greek) accurately describes its characteristic corkscrew appearance. "jejuni" refers to the jejunum, which is the part of the intestine in mammals that is often damaged by infection.
These flagellated gram-negative bacteria colonize the mucosal membranes of the intestinal tracts in cattle, sheep, and birds (see Habitat) where they are often commensal. It's a different story if they find their way into your intestinal tract however. Infection commonly results in gastroenteritis with intense, sometimes bloody diarrhea. Sometimes these guys even go as far as mimicking substances found in human brain/nerve cells and get the immune system to attack itself (see Pathology).
This website is part of a larger project at MultipleOrgansims.net where you can find all kinds of other fascinating organisms. This web page was created by me, Tyler Rollins. I am a sophomore organismal biology student at the University of Wisconsin-La Crosse.
Go next to Classification to see where this organism fits in the grand scheme of life.