Oxygen Requirements of Bacteria

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Oxygen Requirements of Bacteria

BACKGROUND
The GasPak system is useful for culturing anaerobic bacteria on standard microbiological media because the GasPak generates carbon dioxide and hydrogen. The hydrogen will combine with oxygen present in an anaerobic jar to produce water. This system can reproducibly attain oxygen levels in the parts per million range if used correctly. This is the best method for determining the oxygen requirements of unknown organisms.

A candle jar is useful for culturing organisms which prefer reduced oxygen levels and increased carbon dioxide levels. The candle jar is not an oxygen free system. This is the best method of culturing a microaerophile.

An obligate anaerobe is a microbe that cannot tolerate oxygen and will be killed in its presence. This type of organism is killed because it lacks the enzymes necessary to eliminate toxic oxygen products.

An obligate aerobe is a bacterium that requires atmospheric levels of oxygen for normal growth.

A facultative anaerobe is a microorganism that can grow with or without oxygen but usually grows faster (produces more ATP) in its presence.

An aerotolerant anaerobe is a microbe which will survive but will not grow in the presence of oxygen.

A microaerophile is an organism which requires reduced levels of oxygen.

A sodium thioglycollate broth tubes contains substances which chemically combine with oxygen making it unavailable. Anaerobes will grow in this medium. Aerobes can also grow but only in the upper layers of this medium.

PURPOSETo identify bacteria based on growth in oxygen at differing levels.

CULTURESPseudomonas aeruginosa or Micrococcus luteus, Clostridium, Escherichia coli (Aerobes) (Anaerobe) (Facultative anaerobe)

MEDIA3 TSA plates (for anaerobic chamber)

CULTURE CONDITIONS
Lightly streak 4 quadrants on TSA agar for anaerobic chamber. Make sure you can’t see...
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