What does Simmons citrate test for?
Simmons citrate agar tests the ability of organisms to utilize citrate as a carbon source. Simmons citrate agar contains sodium citrate as the sole source of carbon, ammonium dihydrogen phosphate as the sole source of nitrogen, other nutrients, and the pH indicator bromthymol blue.
What grows on Simmons citrate agar?
Simmons Citrate agar is used to test an organism’s ability to utilize citrate as a source of energy. Ammonium Dihydrogen Phosphate is the sole source of nitrogen. Bacteria that can grow on this medium produce an enzyme, citrate-permease, capable of converting citrate to pyruvate.
Is E coli citrate positive?
Klebsiella pneumoniae and Proteus mirabilis are examples of citrate positive organisms. Escherichia coli and Shigella dysenteriae are citrate negative.
How do you make citrate agar slant?
Preparation of Simmons Citrate Agar
- Suspend 24.28 grams in 1000 ml distilled water.
- Heat, to boiling, to dissolve the medium completely.
- Mix well and distribute in tubes or flasks.
- Sterilize by autoclaving at 15 lbs pressure (121°C) for 15 minutes.
- Cool in slanted position (long slant, shallow butt).
What does a positive results indicate in the citrate test?
A positive reaction shows that the organism can use citrate but not necessarily as the sole carbon source.
Is Simmons citrate complex or synthetic?
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.
Which media is used for citrate test?
Citrate agar is used to test an organism’s ability to utilize citrate as a source of energy. The medium contains citrate as the sole carbon source and inorganic ammonium salts (NH4H2PO4) as the sole source of nitrogen.
Is Salmonella typhi citrate positive or negative?
Biochemical Test and Identification of Salmonella Typhi
| Characteristics | Salmonella Typhi |
|---|---|
| Catalase | Positive (+ve) |
| Citrate | Negative (-ve) |
| Flagella | Positive (+ve) |
| Gas | Negative (-ve) |
Why is the citrate test selective?
The citrate utilization test is selective because only certain bacteria can utilize citrate in place of a fermentable carbohydrate.
What is Simmons citrate agar used for?
Simmons Citrate Agar. 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.
What is the composition of citrate media?
Initially the citrate medium was developed by Koser containing ammonium salt as the only nitrogen source and citrate as the only carbon source for differentiating Escherichia coli and Enterobacter aerogenes by IMViC tests. Later on Simmons modified Koser’s formulation by adding agar and bromo thymol blue.
What is citrate agar used for in microbiology?
Simmons Citrate Agar may be used to differentiate citrate-positive Salmonella enteritidis and members of Salmonella subgenus II, III and IV from the citrate-negative Salmonella typhi, Salmonella paratyphi A, Salmonella pullorum and Salmonella gallinarum.
What happens to bromthymol blue indicator when citrate is metabolized?
When the bacteria metabolize citrate, the ammonium salts are broken down to ammonia, which increases alkalinity . The shift in pH turns the bromthymol blue indicator in the medium from green to blue above pH 7.6. It is used for the differentiation of Gram-negative bacteria on the basis of citrate utilization.