A general medium used in lab can be either a liquid broth or solid agar . We use in our lab tryptic soy broth and agar, a chemically undefined medium with beef extract. Another common general medium is nutrient broth or agar. Some labs use a chemically defined specific medium, sometimes designed for a particular species as a minimal medium . This means that each component of the medium is known and measured, and the overall medium contains only those necessary components for a particular organism s growth.
Selective media is designed to inhibit one category of organisms and encourage others.
Differential media is designed to allow more than one type to grow, but have visibly observed results which can serve to indicate differences between the various types of organisms. Ed. III, pp. There are three over-lapping ranges defined to describe categories of organisms with respect to temperature requirements. Thermophiles exist in temperatures above 50 o C, and include the extremophiles of archeobacteria. One of the functions of the prokaryotic cell wall is to keep the cell from bursting in hypotonic environments.