Urea Hydrolysis
DESCRIPTION
Testing the ability  to produce urease, an enzyme that hydrolyse urea providing a source of nitrogen for bacteria.
NOTES
False positives may result due to protein hydrolysis when incubation is prolonged.
REFERENCES:
1. H. Raducanescu, V.Bica-Popii,1986. Bacteriologie veterinara, Ed. Ceres, Bucuresti.
2. Murray, P.R., Baron, E. J., Jorgensen, J.J., Pfaller, M.A., and Yolken, R.H. Manual of Clinical Microbiology, 8th ed. ASM Press:
Washington, DC, 2003.
Christensen's urea agar
positive (left) & negative (right)
PROCEDURE
Pick a well isolated colony and inoculate medium. Incubate 24 hours at 37 °C.
Reaction is positive if the medium become red (urea is decomposed resulting ammonia which changes the pH).
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MEDIUM PREPARATION
Composition of Christensen's  urea agar medium:
Glucose ................................................................................1g
Peptone ................................................................................1g
KH2PO4 ...............................................................................2g
NaCl ......................................................................................5g
Phenol red ...................................................................0.012g
Agar ....................................................................................20g
H
2O ad 1000 ml,  pH = 6.8

To base medium add 20 ml urea solution 20% before solidification. Initial color of the
medium must be yellow.
MIU medium may also be used for urease testing. To MIU base medium add 10 ml
urea sol. 40%.
R E G N U M
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