Microbiology Lab 5-4, 5-5
all aerobic organisms can tolerate
oxygen
Catalase Test results:
(+) = bubbles, catalase present (-) = no bubbles; catalase is absent/not detectable
cytochrome c can catalyze the
reduction of chrochrome c by a *chromogenic reducing agent*
flavoprotein
-ETC carrier -can bypass the next carrier in the chain and transfer electrons directly to oxygen which produced hydrogen peroxide
Obligate anaerobe
-superoxide dismutase absent -catalase absent
Aerotolerant anaerobe
-superoxide dismutase present -catalase absent --> alternative mechanism
obligate aerobe
-superoxide dismutase present -catalase present
microaerophile
-superoxide dismutase present -catalase present in small amounts
facultative anaerobe
-superoxide dismutase present -catalse present
Catalase Test summary:
1. nutrient agar 2. substrate = H2O2 3. enzyme = catalase 4. reduction 5. EPI = O2 6. no reagent/indicator
Oxidase Test summary:
1. nutrient agar --> grow organisms 2. substrate = cytochrome-C 3. cyto-c-oxidase 4. reduction 5. EPI= water 6. reagent= chromogenic reducing agent
cyto C -->
H20
catalase mediated conversion of hydrogen peroxide formula
H2O2 ---> H20 + O2
obligate anaerobes cannot tolerate
O2
superoxide dismutase
catalyzes conversion of superoxide radical to hydrogen peroxide
Cyto C + CRA -->
color
chromogenic reducing agents are chemicals that develop
color as they become oxidized
catalase
convert hydrogen peroxide into water and gaseous oxygen
the oxidase test is designed to identify the presence of
cytochrome c oxidase
hydrogen peroxide is a
highly reactive for organisms that can use O2
Cytochrome C oxidase
the last enzyme in the chain, it makes the final electron transfer of the chain from cytochrome c to oxygen inside the cell
Results of oxidase test
(+) = dark blue/purple within 20 sec, cytochrome c oxidase is present (-) = no color change to blue/purple within 20 sec, cyctochrome c oxidase is not present or not detectable
the catalase test is designed to differentiate bacteria based on their ability to
respire
