Pure culture

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A culture of Bacillus anthracis
A culture of Bacillus anthracis

A microbiological culture, AKA microbial culture, is a method of multiplying microbial organisms by letting them reproduce in predetermined culture media under controlled laboratory conditions. Microbial cultures are used to determine the type of organism, its abundance in the sample being tested, or both. It is one of the primary diagnostic methods of microbiology and used as a tool to determine the cause of infectious disease. Microbial cultures are also used extensively as a research tool in molecular biology. It is often essential to isolate a pure culture of microorganisms. A pure (or axenic) culture is a population of cells or multicellular organisms growing in the absence of other species or types. A pure culture may originate from a single cell or single organism, in which case the cells are genetic clones of one another.

Contents

Bacterial culture

The most common evolution of microbiological culture uses petri dishes with a layer of agar-based growth medium in them to grow bacterial cultures. This is generally done inside of an incubator. Another method is liquid culture, where the bacteria are grown suspended in a liquid nutrient medium. Bottles of liquid culture are often placed in shakers in order to introduce oxygen to the liquid and maintaining the uniformity of the culture.

Virus and phage culture

Virus or phage cultures require host cells for the virus or phage to multiply in. For bacteriophages, cultures are grown by infecting bacterial cells. The phage can then be isolated from the resulting plaques in a lawn of bacteria on a plate. Virus cultures are obtained from their appropriate eukaryotic host cells.

Eukaryotic cell culture

Main article: Cell culture

The term culture can also apply to eukaryotic microorganisms such as yeast and be used as a synonym for tissue culture, which involves the growth of cells or tissues explanted from a multi-cellular organism.

Isolation of pure cultures

For single-celled eukaryotes, such as yeast, the isolation of pure cultures uses the same techniques as for bacterial cultures. Pure cultures of multicellular organisms are often more easily isolated by simply picking out a single individual to initiate a culture. This is a useful technique for pure culture of fungi, multicellular algae, and small metazoa, for example.

Developing pure culture techniques is crucial to the observation of the specimen in question. The most common method to isolate individual cells and produce a pure culture, is to prepare a streak plate. The streak plate method is a way to physically separate the microbial population, and is done by spreading the inoculum back and forth with an incoluating loop over the solid agar plate. Upon incubation, colonies will arise and hopefully single cells will have been isolated from the biomass.

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  • This page was last modified on 23 September 2008, at 22:00.

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