Question

B. Citrate Test. • This is a test for citrate utilization. Identifies bacteria capable of using citrate as a sole carbon source. • These bacteria produce the enzyme Citrate Permease that works in conjunction with Citrate Lyase to produce the end products • Utilization of citrate involves the breakdown of citrate to oxaloacetate and acetate. Oxaloacetate is in turn broken down to Pyruvate and CO, Utilization of ammonium salts in the medium produces ammonium hydroxide that renders the medium alkaline together with carbonates formed by the release of CO TEST MEDIUM Simmon's Citrate slant. Contains Ammonium dihydrogen phosphate and Sodium citrate (or simply Ammonium citrate). pH indicator Bromothymol blue :- Dark Green in neutral pH and deep blue in alkaline pH (from pH > 7.6) Inoculate each test bacterium into separate Simmon's Citrate tubes. Incubate at 37'C for 48 hours. Also incubate an uninoculated tube as negative control. Negative Citrate test à No growth will be visible and no color change from dark green Positive Citrate test à Visible growth and color change from dark green to deep blue. RESULTS After incubation, examine the tubes for growth and color change. Observe for Growth Color change Interpretation Uninoculated Tube Ne Growth Green Bacteria 1. Escherichia coli No Growth Green 2. Serratia Growth Deep Blue 3. Enterobacter Growth Deep Blue 4. Profes Growth Deep Blue S. Shigella No Growth Green 6. Salmonella not Typhi or Paratyphi) Growth Deep Blue 7. UNKNOWN No Growth Green Identify the Unknown bacterium QUESTION: 1. Write in your interpretation of the result for each organism in the numbered spaces, 1 - 6 2. From the results provided in the table suggest the likely identity of the unknown bacterium.