Oxygen requirements vary among microorganisms.
LEARNING OBJECTIVE [ edit ]
Identify the role of oxygen in microbial growth
KEY POINTS [ edit ]
An aerobic organism or aerobe is an organism that can survive and grow in an oxygenated
environment.
An anaerobic organism or anaerobe is any organism that does not require oxygen for growth.
Normal microbial culturing occurs in an aerobic environment which poses a problem when
culturing anaerobes; requiring one of a number of techniques to be used to keep oxygen out of the
culturing setup.
TERMS [ edit ]
aerotolerant anaerobe
an organism that does not require oxygen to sustain its metabolic processes, but is able to survive
in the presence of oxygen
aerobic respiration
metabolic reactions and processes that take place in the cells of organisms and require oxygen to
convert biochemical energy from nutrients into adenosine triphosphate (ATP)
anaerobic
Without oxygen; especially of an environment or organism.
aerobic
Living or occurring only in the presence of oxygen.
Give us feedback on this content: FULL TEXT [edit ]
An aerobic organism or aerobe is an
organism that can survive and grow in an
oxygenated environment. Several varietis
of aerobes exist . Obligate aerobes require
oxygen for aerobic cellular respiration. In
a process known as cellular respiration,
these organisms use oxygen to
oxidize substrates(for example sugars and
fats) in order to obtain
energy.Facultative anaerobes can use
oxygen, but also have anaerobic (i.e. not
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requiring oxygen) methods of energy production. Microaerophiles are organisms that may
use oxygen, but only at low concentrations. Aerotolerant organisms can survive in the
presence of oxygen, but they are anaerobic because they do not use it as a terminal electron
acceptor.
Identity of aerobic and anaerobic bacteria
Aerobically different bacteria behave differently when grown in liquid culture: 1) Obligate aerobic
bacteria gather at the top of the test tube in order to absorb maximal amount of oxygen. 2) Obligate
anaerobic bacteria gather at the bottom to avoid oxygen. 3) Facultative bacteria gather mostly at
the top, since aerobic respiration is advantageous (ie, energetically favorable); but as lack of oxygen
does not hurt them, they can be found all along the test tube. 4) Microaerophiles gather at the upper
part of the test tube but not at the top. They require oxygen, but at a lower concentration. 5)
Aerotolerant bacteria are not affected at all by oxygen, and they are evenly spread along the test
tube.
An anaerobic organism or anaerobe is any organism that does not require oxygen for growth.
It could possibly react negatively and may even die if oxygen is present. For practical
purposes there are three categories : obligate anaerobes, which cannot use oxygen for growth
and are even harmed by it. Aerotolerant organisms, which cannot use oxygen for growth, but
tolerate the presence of it. And finally, facultative anaerobes, which can grow without oxygen
but can utilize oxygen if it is present.
Since normal microbial culturing occurs in atmospheric air, which is an aerobic environment,
the culturing of anaerobes poses a problem. Therefore, a number of techniques are employed
by microbiologists when culturing anaerobic organisms, for example, handling the bacteria in
a glovebox filled with nitrogen or the use of other specially-sealed containers.
Glovebox
Terra Universal 100 Glovebox
The GasPak System is an isolated container that achieves an anaerobic environment by
the reaction of water with sodium borohydride and sodium bicarbonate tablets to produce
hydrogen gas and carbon dioxide. Hydrogen then reacts with oxygen gas on a palladium
catalyst to produce more water, thereby removing oxygen gas.