So we don't take much notice of phosphates but now they have discovered bacteria can use arsenic.
http://uk.news.yahoo.com/18/20101203/tsc-nasa-finds-new-form-of-life-on-earth-e123fef.html
http://uk.news.yahoo.com/18/20101203/tsc-nasa-finds-new-form-of-life-on-earth-e123fef.html