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Aesculin is a glucoside
Glucoside

A glucoside is a glycoside that is derived from glucose. Glucosides are common in plants, but rare in animals. Glucose is produced when a glucoside is Hydrolysis by purely chemical means, or decomposed by fermentation or enzymes....
 that naturally occurs in the horse chestnut (Aesculus hippocastanum), California Buckeye (Aesculus californica
Aesculus californica

Aesculus californica is a species of Aesculus endemic to California, and the only buckeye native to the state.It is a large shrub or small tree growing to 4-12 m tall, with gray bark often coated with lichens or mosses....
) and in daphnin (the dark green resin of Daphne mezereum
Daphne mezereum

Daphne mezereum is a species of Daphne in the flowering plant family Thymelaeaceae, native to most of Europe and western Asia, north to northern England and central Scandinavia....
).

ulin is used in a microbiology laboratory to aid in the identification of bacterial species (especially Enterococci
Enterococcus

Enterococcus is a genus of lactic acid bacteria of the Phylum Firmicutes. Members of this genus were classified as Group D Streptococcus until 1984 when genomic DNA analysis indicated that a separate genus classification would be appropriate....
).

ulin is incorporated into agar with ferric citrate and bile salts (bile aesculin agar).






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Aesculin is a glucoside
Glucoside

A glucoside is a glycoside that is derived from glucose. Glucosides are common in plants, but rare in animals. Glucose is produced when a glucoside is Hydrolysis by purely chemical means, or decomposed by fermentation or enzymes....
 that naturally occurs in the horse chestnut (Aesculus hippocastanum), California Buckeye (Aesculus californica
Aesculus californica

Aesculus californica is a species of Aesculus endemic to California, and the only buckeye native to the state.It is a large shrub or small tree growing to 4-12 m tall, with gray bark often coated with lichens or mosses....
) and in daphnin (the dark green resin of Daphne mezereum
Daphne mezereum

Daphne mezereum is a species of Daphne in the flowering plant family Thymelaeaceae, native to most of Europe and western Asia, north to northern England and central Scandinavia....
).

Medical uses

Aesculin is used in a microbiology laboratory to aid in the identification of bacterial species (especially Enterococci
Enterococcus

Enterococcus is a genus of lactic acid bacteria of the Phylum Firmicutes. Members of this genus were classified as Group D Streptococcus until 1984 when genomic DNA analysis indicated that a separate genus classification would be appropriate....
).

Aesculin hydrolysis test

Aesculin is incorporated into agar with ferric citrate and bile salts (bile aesculin agar). Hydrolysis of the aesculin forms aesculetin (6,7-dihydroxycoumarin
Coumarin

Coumarin is a chemical compound ; a toxin found in many plants, notably in high concentration in the tonka bean, vanilla grass, woodruff, mullein, and bison grass....
) and glucose
Glucose

Glucose , a monosaccharide also known as grape sugar, blood sugar, or corn sugar, is a very important carbohydrate in biology....
. The aesculetin forms dark brown or black complexes with ferric citrate, allowing the test to be read.

The bile aesculin agar is streaked and incubated at 37°C for 24 hours. The presence of a dark brown or black halo indicates that the test is positive. A positive test can occur with Enterococcus
Enterococcus

Enterococcus is a genus of lactic acid bacteria of the Phylum Firmicutes. Members of this genus were classified as Group D Streptococcus until 1984 when genomic DNA analysis indicated that a separate genus classification would be appropriate....
, Aerococcus and Leuconostoc
Leuconostoc

Leuconostoc is a genus of Gram-positive bacterium, placed within the family of Leuconostocaceae. They are generally ovoid cocci often forming chains....
. Aesculin will fluoresce under long wave ultraviolet
Ultraviolet

Ultraviolet light is electromagnetic radiation with a wavelength shorter than that of visible light, but longer than x-rays, in the range 400 nanometer to 10 nm, and energies from 3 Electron volt to 124 eV....
 light (360 nm): hydrolysis of aesculin results in loss of this fluorescence.

Enterococcus will often flag positive within four hours of the agar being inoculated.

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