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Jan 26, 2016 · Agar, a jelly-like substance derived from seaweed species of the genus Gelidium, is perhaps microbiology’s most important laboratory reagent, long used as a solid substrate to culture and isolate bacteria.
- Sim Shuzhen
ABOUT. Shuzhen received a PhD degree from the Johns Hopkins...
- Sim Shuzhen
[19] Agar was first subjected to chemical analysis in 1859 by the French chemist Anselme Payen, who had obtained agar from the marine algae Gelidium corneum. [20] Beginning in the late 19th century, agar began to be used as a solid medium for growing various microbes.
- Bacteriological Agar
- Usage History
- Chemical Nature
- Agarose
- Uses
- Alternatives
Bacteriological agar is a hydrophilic colloidal substance made from cell wall components of Gelidium and Rhodoyceae (marine algae) species. Agar is used to solidifying culture media because of its high gelling strength; a setting temperature of 32-39°C, and a melting temperature of 90-95°C. Low gelling temperature (34-36°C) allows the addition of h...
Angelina Fanny Hesse (1850-1934) was the first to propose agar use in culture media.She is the wife of one of Robert Koch’s colleagues, Walther Hesse. Ironically, neither Lina nor Walter Hesse was given credit for using agar in microbiology. Fanny Hesse suggested Robert Koch to add agar to his bacteriological media. The use of agar created a firm s...
Agar (also called agar-agar) is a mixture of polysaccharides whose basic monomer is galactose. Agar consists of two fractions,agarose and agaropectin. Agarose is a linear polysaccharide and the gel-forming component; agaropectin is a branched, nongelling component of agar. Agar is a creamy white powder soluble in hot water but insoluble in cold wat...
Agarose is a neutral, long-chain polysaccharide formed by alternating D-galactose and 3,6-anhydro-alpha-L-galactopyranose residues joined by alpha-(1->3)- and beta-(1->4)-linkages. This electrically neutral polysaccharide is suitable for electrophoresis and chromatography.
Agar is widely used in many industries due to its ability to form a gel. The large difference between gel-forming and melting temperatures gives agar its unique properties. 1. Bacteriological agar is an indispensable ingredient in diagnostic labs and research projects, e.g., culture and AST, tissue culture, cell assays, etc. Due to the ease with wh...
Apart from agar, media can be solidified by incorporating a gelling agent such as gelatin. Researches are underway to find newer and cost-effective alternatives to bacteriological agar. Some possible candidates are; low-cost food-grade agar, cellulose produced by engineered bacteria, and fewer alternative gelling agents. References and further read...
Agar is a polysaccharide derived from red seaweeds, and proved to be a superior gelling agent. Agar has remarkable physical properties: it melts when heated to around 85oC, and yet when cooled doesn’t gel until 34-42oC. Agar is also clearer than gelatin and it resists digestion by bacterial enzymes.
Sep 19, 2024 · Agar is isolated from the algae as an amorphous and translucent product sold as powder, flakes, or bricks. Although agar is insoluble in cold water, it absorbs as much as 20 times its own weight. It dissolves readily in boiling water; a dilute solution is still liquid at 42 °C (108 °F) but solidifies at 37 °C (99 °F) into a firm gel.
- The Editors of Encyclopaedia Britannica
This article will plunge into the depths of agar, unveiling its definition, role, and the intriguing process behind its production. It will dissect the different types of agar used in microbiology, such as Nutrient agar, MacConkey agar, and Sabouraud agar, explaining their particular uses.
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Chemically, agar is a polymer made up of subunits of the sugar galactose, and is a component of the cell walls of several species of red algae that are usually harvested in eastern Asia and California. Dissolved in boiling water and cooled, laboratory agar looks gelatinous.
