"Rhizopus microsporus" lives as a necrotroph where both the fungus ("Rhizopus microsporus") and its harbored endobacteria ("Burkholderia rhizoxinica") form a symbiotic relationship. In order to kill the living cells of its host, the harbored endobacteria secrete rhizoxin, a toxin that inhibits cell mitosis and vegetative production. "R. microsporus" has developed a resistance to the toxin due to an amino acid exchange in the β-tubulin protein. The resulting necrosis of the plant tissue replenishes nutrients to both the fungus and the bacteria by feeding on the decaying matter.