Impeller
An agitator that is used for mixing the contents of a bioreactor.

Inactivated agent
A virus, bacterium or other organism that has been treated to prevent it from causing a disease.

Inbred line
The product of inbreeding, i.e., the mating of individuals that have ancestors in common; in plants and laboratory animals, it refers to populations resulting from at least 6 generations of selfing or 20 generations of brother, sister mating, that are for all practical purposes, completely homozygous. In farm animals, the term is sometimes used to describe populations that have resulted from several generations of the mating of close relatives, without having reached complete homozygosity.

Incompatibility
1. Selectively restricted mating competence, which limits fertilization, such as lack of proper functions by otherwise normal pollen grains or certain pistils, a condition that may be caused by a variety of factors.
2. A physiological interaction resulting in graft rejection or failure.
3. A function of a related group of plasmids. Plasmids which are closely related share similar replication functions and this leads to the exclusion of one or the other plasmid if they are present in the same cell; thus such plasmids are incompatible. Plasmids are placed in incompatibility groups by this simple reaction and, in general, plasmids belonging to one incompatibility group (q.v.) are very closely related.

Incompatibility group
A classification scheme indicating which plasmids can co-exist within a single cell. Plasmids must belong to different incompatibility groups to coexist within the same cell. Plasmids that belong to the same incompatibility group are unstable when placed in the same cell. A plasmid cloning vector should always belong to an incompatibility group different from that of the host bacterium's endogenous plasmids.