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Nutrient agar is a general purpose liquid
but lacks agar. These ingredients are combined and boiled for approximately one minute to ensure they are mixed and then sterilized by autoclaving, typically at for 15 minutes. Then they are cooled to around and poured into Petri dishes which are covered immediately. Once the dishes hold solidified agar, they are stored upside down and are often refrigerated until used. Inoculation takes place on warm dishes rather than cool ones: if refrigerated for storage, the dishes must be rewarmed to room temperature prior to inoculation.
Nutrient agar is a general purpose liquid medium
Medium may refer to:
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Aviation
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supporting growth of a wide range of non-fastidious
A fastidious organism is any organism that has complex or particular nutritional requirements. In other words, a fastidious organism will only grow when specific nutrients are included in its medium. The more restrictive term fastidious microorga ...
organisms. It typically contains ( mass/volume):
* 0.5% peptone - this provides organic nitrogen
* 0.3% beef extract/yeast extract
Yeast extracts consist of the cell contents of yeast without the cell walls; they are used as food additives or flavorings, or as nutrients for bacterial culture media. They are often used to create savory flavors and umami taste sensations, ...
- the water-soluble content of these contribute vitamins, carbohydrates, nitrogen, and salts
* 1.5% agar - this gives the mixture solidity
* 0.5% sodium chloride - this gives the mixture proportions similar to those found in the cytoplasm
In cell biology, the cytoplasm is all of the material within a eukaryotic cell, enclosed by the cell membrane, except for the cell nucleus. The material inside the nucleus and contained within the nuclear membrane is termed the nucleoplasm. ...
of most organisms
* distilled water
Distilled water is water that has been boiled into vapor and condensed back into liquid in a separate container. Impurities in the original water that do not boil below or near the boiling point of water remain in the original container. Thus, di ...
- water serves as a transport medium for the agar's various substances
* pH adjusted to neutral (6.8) at .
Nutrient broth has the same composition,but lacks agar. These ingredients are combined and boiled for approximately one minute to ensure they are mixed and then sterilized by autoclaving, typically at for 15 minutes. Then they are cooled to around and poured into Petri dishes which are covered immediately. Once the dishes hold solidified agar, they are stored upside down and are often refrigerated until used. Inoculation takes place on warm dishes rather than cool ones: if refrigerated for storage, the dishes must be rewarmed to room temperature prior to inoculation.
See also
*Plate count agar
Plate Count Agar (PCA), also called Standard Methods Agar (SMA), is a microbiological growth medium commonly used to assess or to monitor "total" or viable bacterial growth of a sample. PCA is not a selective medium.
The total number of living a ...
*Bacteria
Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one Cell (biology), biological cell. They constitute a large domain (biology), domain of prokaryotic microorganisms. Typically a few micrometr ...
*Bacterial growth
250px, Growth is shown as ''L'' = log(numbers) where numbers is the number of colony forming units per ml, versus ''T'' (time.)
Bacterial growth is proliferation of bacterium into two daughter cells, in a process called binary fission. Providing ...
References
Further reading
*Lapage S., Shelton J. and Mitchell T., 1970, Methods in Microbiology', Norris J. and Ribbons D., (Eds.), Vol. 3A, Academic Press, London. *MacFaddin J. F., 2000, Biochemical Tests for Identification of Medical Bacteria, 3rd Ed., Lippincott, Williams and Wilkins, Baltimore. *Downes F. P. and Ito K., (Ed.), 2001, Compendium of Methods for the Microbiological Examination of Foods, 4th Ed., American Public Health Association, Washington, D.C. *American Public Health Association, Standard Methods for the Examination of Dairy Products, 1978, 14th Ed., Washington D.C. Microbiological media {{Microbiology-stub