The citrate test screens a bacterial isolate for the ability to utilize citrate as its carbon and energy source (3, 7). A positive diagnostic test rests on the generation of alkaline by-products of citrate metabolism. The subsequent increase in the pH of the medium is demonstrated by the color change of a pH indicator.
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What does the citrate slant test for?
The citrate test screens a bacterial isolate for the ability to utilize citrate as its carbon and energy source (3, 7). A positive diagnostic test rests on the generation of alkaline by-products of citrate metabolism. The subsequent increase in the pH of the medium is demonstrated by the color change of a pH indicator.
What is the purpose of Simmons Citrate agar?
Purpose. This medium is used to aid in the differentiation of various genera in the Enterobacteriaceae. Bacteria that can utilize citrate as the sole carbon source and inorganic ammonium salt as the sole source of nitrogen grow on this medium.
What does Simmons Citrate agar contain?
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.
Is citrate slant selective or differential?
Subscribe us to receive latest notes. 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 organism is positive for citrate test?
Klebsiella pneumoniae and Proteus mirabilis are examples of citrate positive organisms.
What is the function of citrate and what role does it play in the growth of the bacteria?
Growth is indicative of utilization of citrate, an intermediate metabolite in the Krebs cycle. 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.
What type of media is the Simmons Citrate agar?
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.
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. Sodium Citrate is the sole source of carbon in this medium.
How do you make citrate slant?
Preparation of Simmons Citrate Agar Dissolve above salts in deionized water. Adjust pH to 6.9. Add agar and Bromothymol blue. Gently heat, with mixing, to boiling until agar is dissolved.
Which organism is citrate test positive?
Klebsiella pneumoniae and Proteus mirabilis are examples of citrate positive organisms. Escherichia coli and Shigella dysenteriae are citrate negative.
What type of indicator does the citrate test use?
Bacteria are inoculated on a medium containing sodium citrate and a pH indicator such as bromothymol blue.
What is the substrate for citrate test?
What is the substrate for the Citrate Agar? An enzyme called citrase will catabolize the citrate into oxaloacetic acid and acetic acid. Acetic acid to CO2.
What enzymes does citrate regulate?
Citrate is synthesized inside the mitochondria by citrate synthase from acetyl-CoA and OAA. It is exported outside the mitochondria by CIC. Citrate inhibits PFK1, PK, PDH, and SDH.
What organism is citrate positive?
Which media is used for citrate utilization test?
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 bacteria can use citrate?
How do you do a citrate slant?
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 broth is used for citrate test?
Simmons Citrate Agar is an agar medium used for the differentiation of Enterobacteriaceae based on the utilization of citrate as the sole source of carbon….Ingredients per liter of deionized water:*
| Ingredients | |
|---|---|
| Sodium Chloride (NaCl) | 5.0 gm |
| Sodium Citrate (dehydrate) | 2.0 gm |
| Ammonium Dihydrogen Phosphate | 1.0 gm |