Citrate of Simmons

Use

Use of citrate like only source of carbon.

Composition

- Citrate of sodium: ................................................ 1,0 G - bromothymol blue: .............................................. 0,08 G - Sodium chloride: ............................................... 5,0 G - Epsom salt: ............................................. 0,2 G - potassium hydrogénophosphate: .................................. 1,0 G - ammonium dihydrogénophosphate: .................................. 1,0 G - Agar: ............................................................ 15,0 G

pH = 7,1

Preparation

23 G per liter. Traditional sterilization by pressure-sealing. Conditioning out of tilted tubes.

Mode of action

This medium contains only one source of carbon; the citrate. Only the bacteria having a citrate perméase will be able to develop on this medium. The use of citrate can be made in various ways, which according to the case, will result in an alkalization or an acidification of the medium, more or less important. By convention one will classify a bacterium in the citrates+ if it uses citrate by alkalizing the medium. Citrate + citric 3:2 O → Acid + 3OH- Enzyme

A bacterium will be citrate more if it alkalizes the medium by using citrate. This reaction is indicated by the change of color of the indicator of pH, the bromothymol blue which becomes blue.

Note: so that the reaction is done in the way just possible, the material used will be cleanest possible in order to not contain aucunes organic particles which could distort the result. to work in sterile medium and with sterile material is best the solution.

Reading

The bacteria using citrate as only source of carbon normally turn blue the medium (alkalization) the bacteria not using it do not cultivate. However, of the bacteria can use citrate like alone source of carbon without turning blue ( Enterococcus )

ATTENTION: the stopper must be emerged for incubation.

to see too

Culture medium
Culture media (list)

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