teratoma. [terâ²ÉtÅâ²mÉ] pl. teratomas, teratomata. a tumor composed of different kinds of tissue, none of which normally occurs together or at the site of the tumor. Teratomas are most common in the ovaries or testes.
The pink-colored film or ring frequently seen on showers, tubs, toilets and pet water bowls is typically caused by growth of the airborne bacteria Serratia marcesens. This harmless nuisance organism reacts with standing water and frequently forms during spring and summer months.
Bacteria that stain purple with the Gram staining procedure are termed Gram-positive; those that stain pink are said to be Gram-negative. The terms positive and negative have nothing to do with electrical charge, but simply designate two distinct morphological groups of bacteria.