Colony-forming unit

A colony forming unit (abbreviated CFU or CFU ) is a quantity which plays a role in the quantitation of microorganisms, namely, if the number of microorganisms is determined in a material way the cultural. The English name is Colony Forming Unit, CFU abbreviated.

Microorganisms can be quantified, among others with cultural methods. It mostly a sample of the material whose level of microorganisms is to be determined is distributed evenly on the surface of a culture medium gel or in the culture medium gel, so that, ideally, individually all individuals of the microorganisms and far enough to be away from each other come and at appropriate culture conditions each form a visible with the eye colony by growth and reproduction. The number of colonies under these ideal conditions, equal to the number of individuals in the sample. In fact, come under real conditions, some individuals are so close together that they form only a single common colony, also often adhere to some individuals so tightly together that they can not be separated and also just developed a colony of it. Under real, non-ideal conditions that is, the number of colonies is less than the number of individuals in the sample. Therefore, the term colony forming unit was introduced, which corresponds to both individuals as well as several adherends or lying close together individuals.

A special feature of the method to quantify using a culture and by determining the number of colony forming units microorganisms is that by the choice of culture conditions ( culture medium, temperature, oxygen availability, and the like ) in microorganisms companies with species different demands on the provide culture conditions, often only a selection of all occurring microorganisms is detected. This can be advantageous if only certain physiological types are to be detected by micro-organisms. The disadvantage is that if a so-called bioburden is to be determined in a mixed micro - society, ie the total number of microorganisms present.