The chemical on which an enzyme acts. It binds to the enzyme and is converted into a product or products through the action of the enzyme.

A dose of drug that is below the level required to treat disease.

A single amino acid chain that forms a protein in complex with other subunits.

When two substances act together to create an effect that is greater than the effect seen when using either substance alone.

A genetically determined characteristic of an organism.

A technique that identifies which genes are being expressed in cells.

A horizontal gene transfer mechanism in which bacteria take up plasmids from the environment across the cell wall.

The passing of disease-causing pathogens from one individual to another.

A measure of how well light passes through a liquid. Light is scattered by particles in liquid, making them appear cloudy, or turbid. Turbidity can be used to measure bacterial cell density. Samples with a high cell density will appear more turbid than those with a low cell density.