Growth Media Function and Application
Growth media is a substance which supports cellular growth. Given the array of microorganisms, so too are the types of growth media to match the life support parameters microorganisms may require. Typical growth media are liquid nutrient mediums (like lysogeny broth) and nutrient broths with the addition of agar. Once the broth is cooled, the agar allows for the nutrient broth to solidify (usually in Petri dishes), to allow for a nutrient-rich surface for cellular colonies to grow.
Growth Media Types
There are two types of growth media: defined and undefined. As the name suggests, a defined medium has a set quantity of known ingredients. This arises from extensive study of all the required elements, vitamins, and other molecules needed to grow a cellular organism. Undefined medium has added complexity in that some ingredients contain an unknown proportion of chemical mixtures. An example of this that is common in the lab is a yeast extract or casein hydrolysate. It is challenging to quantify all the required nutrients for cellular organisms. That is why some microorganism have never been grown on defined media.
Culture Media: Contains all the nutrients required for bacteria, and are usually not selective. They usually have glucose as a carbon source, water, various salts, amino acids, and nitrogen.
Minimal Media: Contains the minimum amount of nutrients possible for colony growth. This is usually used to determine recombinant or exconjugates, and to grow wild-type versions of the target organism.
Selective Media: A common method used in cell culturing, this media contains antibiotics in order to grow selected cells. A typical example of this is with ampicillin. Those bacteria which contain resistance to ampicillin then would be allowed to grow on the media.
Differential Media: Contains chemical mixtures to distinguish various cells. This is used to determine the presence of microorganisms visually.
Transport Media: only used to store and transfer target specimens temporarily