Question

A single colony on a plate that is isolated is assumed to be a pure culture. Explain why this is so.

Answer 1

Pure culture, in microbiology is a laboratory culture containing a single species of organism. A pure culture is usually derived from a mixed culture (one containing many species) by transferring a small sample into new, sterile growth medium in such a manner as to disperse the individual cells across the medium surface or by thinning the sample many fold before inoculating the new medium. Both methods separate the individual cells so that, when they multiply, each will form a discrete colony, which may then be used to inoculate more medium, with the assurance that only one type of organism will be present. Isolation of a pure culture may be enhanced by providing mixed inoculums with a medium favoring the growth of one organism to the exclusion of others.