What is the purpose of Simmons citrate agar explain how it works?
Simmons’ citrate agar is a selective and differential medium that tests for an organism’s ability to use citrate as a sole carbon source and ammonium ions as the sole nitrogen source. It is used for differentiating gram-negative bacteria on the basis of citrate utilization.
Which enzyme does the Simmons citrate agar test for?
enzyme citrase
Simmon’s Citrate Agar It is often used to differentiate between members of Enterobacteriaceae. In organisms capable of utilizing citrate as a carbon source, the enzyme citrase hydrolyzes citrate into oxaoloacetic acid and acetic acid. The oxaloacetic acid is then hydrolyzed into pyruvic acid and CO2.
What is the purpose of citrate utilization test?
Citrate utilization is a metabolic test used to determine an organism’s ability to utilize citrate as its lone source of carbon. Simmons citrate agar is a synthetic medium containing citrate, ammonium ions, and the pH indicator bromthymol blue. This indicator is green below pH 7.6 and blue above pH 7.6.
What are the buffers in Simmons citrate medium?
Ammonium Dihydrogen Phosphate is the sole source of nitrogen in Simmons Citrate Agar. Dipotassium Phosphate acts as a buffer. Sodium Chloride maintains the osmotic balance of the medium.
What is the principle of citrate test?
Principle. Bacteria are inoculated on a medium containing sodium citrate and a pH indicator such as bromothymol blue. The medium also contains inorganic ammonium salts, which are utilized as sole source of nitrogen. Use of citrate involves the enzyme citrase, which breaks down citrate to oxaloacetate and acetate.
How do you perform Simmons citrate test?
Procedure
- Obtain a slant of Simmons Citrate Agar.
- Using an inoculating needle, stab your assigned organism into the medium, then zigzag the needle back and forth up the surface of the slant.
- Incubate the tube for at least 48 hours.
- After the incubation period, examine the slant.
Which media is used for citrate utilization test?
Media Used Simmon’s Citrate agar is used as the medium to test the ability of an organism to utilize citrate as a sole source of energy.
What are the ingredients of Simmon citrate agar?
Ingredients per liter of deionized water:*
| Sodium Chloride (NaCl) | 5.0 gm |
|---|---|
| Sodium Citrate (dehydrate) | 2.0 gm |
| Ammonium Dihydrogen Phosphate | 1.0 gm |
| Dipotassium Phosphate | 1.0 gm |
| Magnesium Sulfate (heptahydrate) | 0.2 gm |
What is the Colour of citrate?
Citrate positive: growth will be visible on the slant surface and the medium will be an intense Prussian blue. The alkaline carbonates and bicarbonates produced as by-products of citrate catabolism raise the pH of the medium to above 7.6, causing the bromothymol blue to change from the original green color to blue.
What is the end product of citrate test?
The citrate test identifies the use of citrate as a sole carbon source, since there are no other nutrients in this medium. The basic end products (carbonates, bicarbonates, and ammonium hydroxide) will cause the brom thymol blue indicator in the medium to turn from forest green to royal blue.
What is Simmons citrate medium used for?
Principle. Simmons’ citrate agar is used for differentiating gram-negative bacteria on the basis of citrate utilization. It is useful for selecting for organisms that use citrate as its main carbon and energy source.
How do you test for citrate?
Procedure of Citrate Utilization Test
- Streak the slant back and forth with a light inoculum picked from the center of a well-isolated colony.
- Incubate aerobically at 35 to 37 C for up to 4-7 days.
- Observe a color change from green to blue along the slant.
