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Hydrolysis of Urea by Bacteria

Identifying bacteria by the presence of urease enzyme

Inna Polyakova

on 18 October 2013

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Transcript of Hydrolysis of Urea by Bacteria

Adithi, Inna, Kalinda, Kiara Urea and Urease Background Information 1917: James Batcheller Sumner discovered that urease is an enzymatic protein
Urease catalyzes urea hydrolysis into CO2 and NH3
(NH2)2CO + H2O --> CO2 + 2NH3
ammonia = easy source of nitrogen for bacteria
reaction involving bacteria hypothesized by Reoch (1875)
Urease test developed to identify Protease species
Protease very similar to Enterobacter aerogenes (same family)
one of few tests that can distinguish them Urease Test This medium was developed in 1941
has nutrients need for bacterial growth and 2% urea
species that can rapidly convert urea to ammonia (Urease +) --> pink
species with a slower reaction time (delayed +) --> medium remains yellow
medium has pH of 6.8
phenol red = indicator
large NH3 content needed to raise pH above 8.0 for a color change Lower buffer content than Stuart's
added peptone: more nutrients for growth
added dextrose: carbon + energy source
many Enterobacteriaceae can grow and small changes in pH can be detected
rapidly urease (+) = pink within 6 hrs
delayed urease (+) = pink within 6 days
urease (-) = medium remains yellow Christensen's urea broth Ammonia and urea = important sources of nitrogen for bacteria
Urease enzyme - 10% of bacterial protein content
maintaining PH neutral environment
maintaining nitrogenous balance
colonization Importance to Bacteria Positive control
bacteria being tested
Proteus mirabilis
Citrobacter freundii
Klebsiella pneumoniae
Enterobacter cloacae
Staphylococcus aureus
Negative control
bacteria known to be urease (-)
Enterobacter aerogenes
Pseudomonas aeruginosa
Examples Bacteria that are able to use urea as the only source of nitrogen, produce a lot of ammonia, changing the pH drastically and resulting in a clearly detectable color change Stuart's Medium Medical Significance urease helps Helicobacter pylori to colonize the gut
raises pH of gastric juice from 3 to 7 - optimal growth
can contribute to chemotaxis/movement within the stomach to help the bacteria colonize it quickly
can lead to multiple diseases including peptic ulcers, chronic gastritis, and other ulcer complications References Brink, B. (2012). Urease test protocol. American Society for Microbiology: Microbe Library, Retrieved from http://www.microbelibrary.org/library/laboratory-test/3223-urease-test-protocol

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