bio-pathologic 

A created nano organism used expressly for the purpose of consuming another organism in a transformative action, then dying, leaving behind something more useful.

"The bio-pathologic creations were short-lived but very effective in their explicit function: eat and die. Behind them, they left a fertile field of death, assuring that the corpses of any incompatible alien flora would be able to support the intended crops and other flora."
- Todd R. Stevens, Parallel Extinction, soon to be published

bio-pathologic by TigreArts November 20, 2010