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Biology Book

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Biology is the natural science that studies life and living organisms, including their physical structure, chemical processes, molecular interactions, physiological mechanisms, development and evolution
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Simmons Citrate Agar biochemistry test for Enterobacteriaceae

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Simmons Citrate Agar 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: Principle of Simmons Citrate Agar Uses of Simmons Citrate Agar 1.     It is used for the differentiation of Gram-negative bacteria on the basis of citrate utilization. 2.     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 . 3.     Simmons Citrate Agar is primarily used to aid in the identification of Enterobacteriaceae. Uses include: Escherichia coli ...
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Urease Test

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Urease Test The urease test is used to determine the ability of an organism to split urea, through the production of the enzyme urease. Principle  Urea  is the product of decarboxylation of  amino acids . Hydrolysis of  urea  produces  ammonia  and  CO2 . The formation of  ammonia  alkalinizes the medium, and the pH shift is detected by the color change of  phenol red  from  light orange  at pH 6.8 to  magenta (pink)  at pH 8.1. Rapid urease-positive organisms turn the entire medium  pink  within 24 hours. Weakly positive organisms may take several days, and negative organisms produce  no color change  or  yellow  as a result of  acid production . Uses  1.     This test is used to differentiate organisms based on their ability to hydrolyze urea with the enzyme...
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Simmons Citrate Test

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Simmons Citrate Reaction It  used to differentiate among the Gram-Negative bacilli in the family Enterobacteriaceae. Principle  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 . Bacteria that can grow on this medium produce an enzyme,  citrate-permease , capable of converting  citrate  to  pyruvate .  Pyruvate  can then enter the organism’s metabolic cycle for the production of  energy . 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...
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