Transcript Ex. 5-4 Catalase test

Ex. 5-4
Catalase test
MCB 1000 Lab.
Prof. Meléndez
Catalase test

The catalase test is used to detect the
presence of the enzyme catalase in bacteria.
Catalase serves to neutralize the bactericidal
effects of hydrogen peroxide. Its
concentration in bacteria has been
correlated with pathogenicity. This enzymatic
test is essential in the scheme of
identification for gram-positive organisms
and certain gram-negative organisms. It is a
primary test used in the differentiation of
staphylococci and streptococci.
Catalase test

Theory
The catalase enzyme serves to neutralize the
bactericidal effects of hydrogen peroxide .
Catalase expedites the breakdown of hydrogen
peroxide (H2O2- (toxic) into water (H2O) and
oxygen(O2)
2H2O2 + Catalase → 2H2O + O2(gas bubbles)

This reaction is evident by the rapid formation
of bubbles
Catalase test
The catalase test facilitates the detection of the
enzyme catalase in bacteria. It is essential for
differentiating catalase-positive Micrococcaceae
from catalase-negative Streptococcaceae.
 The catalase test is also valuable in differentiating
aerobic and obligate anaerobic bacteria, as
anaerobes are generally known to lack the
enzyme . In this context, the catalase test is
valuable in differentiating aerotolerant strains of
Clostridium, which are catalase negative, from
Bacillus, which are catalase positive

Slide catalase test results. Hydrogen peroxide was added directly to
the culture on a microscope slide. A positive reaction produced by
Staphylococcus aureus is indicated by bubbling; a negative reaction
produced by Streptococcus pyogenes is indicated by lack of
bubbling. (Karen Reiner, Andrews University, Berrien Springs, MI)
Practice questions

Read lab. manual pages 243-246 and fill out following chart: Determine if
situation on first column will cause a false positive or a false negative.
Explain why?
Description of situation
Effect on test
Why?
1. Adding hydrogen peroxide to slide
first, then adding cells and mixing cells
with hydrogen peroxide using loop.
False positive
Metal wire of loop can react
with hydrogen peroxide
causing bubbles due to
oxidation of metal, not the
enzyme activity.
2. Hydrogen peroxide is expired (old)
3. Cells are heat fixed into slide
4. Cells are very old
5. Contamination of culture with
aerobic microorganism
6. Dirty slide was used
References

http://www.microbelibrary.org/index.php/l
ibrary/laboratory-test/3226-catalase-testprotocol

Leboffe, Michael J. , and Burton E. Pierce.
Microbiology Laboratory, Theory and
application: (brief edition). Colorado:
Morton Publishing Company, 2008.