Word of the Day
Agar (AY-gahr)
· Common clues: Seaweed extract; Culture medium; Emulsifying agent; Food thickener
· Crossword puzzle frequency: 6 times a year
· Frequency in English language: 42862 / 86800
Agar is a galactose polymer (or Agarose) obtained from the cell walls of some species of red algae or seaweeds (Sphaerococcus euchema) and species of Gelidium, chiefly from eastern Asia and California. Also known as Kanten, Agar-Agar, or Agal-Agal (Ceylon Agar).
Chemically, agar is a polymer made up of subunits of the sugar galactose; it is a component of the algae's cell walls. Dissolved in hot water and cooled, agar becomes gelatinous; its chief use is as a culture medium for microbiological work. Other uses are as a laxative, a vegetarian gelatin substitute — a thickener for soups, in jellies, ice cream and Japanese desserts such as anmitsu, as a clarifying agent in brewing, and for sizing fabrics.
Nutrient agar is used throughout the world as a medium for the growth of bacteria and fungi, but not viruses.
An
agar plate with microorganisms isolated from a deep-water sponge.
The basic agar formula can be used to grow almost all microbes; however, other more specific nutrient agars are available. For example, blood agar, which is generally combined with horse blood, can be used to detect the presence of haemophoragic micro-organisms such as E.coli O:157 H:7. The bacteria digest the blood, turning the plate clear.
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Agar".
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