Biodesulfurization is a process by which sulfur may be removed from organic compounds using a microorganism (eg, a bacterium). This has been and is currently being researched at various sites around the country, for the simple reason that, around 2004 or 2005 or so, new regulations set forth by the Clinton administration will require levels of sulfur in diesel so low as to make it completely unprofitable to use. As non-biological attempts to solve this problem have serious hurdles including but not limited to hydrogen consumption (which should probably be covered elsewhere), this technology will likely be a cornerstone of diesel refining for years to come. And it involved putting genetically engineered bacteria in diesel, to save the environment. How cool is that?