Life Built With Toxic Chemical: First Known Microbe on Earth Able to Thrive and Reproduce Using Arsenic

http://www.sciencedaily.com/releases/2010/12/101202140622.htm

Too bad they haven't named it yet, but apparently, this organism uses arsenic (chemically similar to phosphorus) instead of phosphorous in it's DNA/RNA, etc.  It was discovered in Mono Lake in California.