Because microorganisms are so small, large populations are generally needed in order to monitor microbial activity. Aseptic techniques help ensure that only one type of microorganism is present in a container (pure culture). These methods also ensure that the microorganisms do not escape from the container, contaminating the laboratory, and possibly causing disease.
The streak plate technique, first developed in Koch's laboratory, allows one type of microorganism to be isolated from a mixed source.
Pure cultures may be subcultured to new media using aseptic transfer methods.