A condition in which injured or diseased body tissue dies due to a lack of blood flow, then becomes infected by bacteria (especially from the genus Clostridium) and begins to decay.

Gangrenous tissue often turns black because bacteria make iron sulfide from the iron in decaying hemoglobin.

From the BioTech Dictionary at http://biotech.icmb.utexas.edu/. For further information see the BioTech homenode.