From Wikipedia, the free encyclopedia
Organism that requires oxygen to grow
Aerobic and anaerobic
bacteria can be identified by growing them in test tubes of
thioglycollate broth : 1: Obligate aerobes need oxygen because they cannot ferment or respire anaerobically. They gather at the top of the tube where the oxygen concentration is highest. 2:
Obligate anaerobes are poisoned by oxygen, so they gather at the bottom of the tube where the oxygen concentration is lowest. 3:
Facultative anaerobes can grow with or without oxygen because they can metabolise energy aerobically or anaerobically. They gather mostly at the top because aerobic respiration generates more ATP than either fermentation or anaerobic respiration. 4:
Microaerophiles need oxygen because they cannot ferment or respire anaerobically. However, they are poisoned by high concentrations of oxygen. They gather in the upper part of the test tube but not the very top. 5:
Aerotolerant organisms do not require oxygen as they metabolise energy anaerobically. Unlike obligate anaerobes however, they are not poisoned by oxygen. They can be found evenly spread throughout the test tube.
An obligate aerobe is an
organism that requires
oxygen to grow.
[1] Through
cellular respiration , these organisms use oxygen to metabolise substances, like sugars or fats, to obtain energy.
[1]
[2] In this type of respiration, oxygen serves as the terminal electron acceptor for the
electron transport chain .
[1]
Aerobic respiration has the advantage of yielding more energy (
adenosine triphosphate or ATP ) than
fermentation or
anaerobic respiration ,
[3] but obligate aerobes are subject to high levels of
oxidative stress .
[2]
Table 1. Terms used to describe O2 Relations of Microorganisms.
[4]
Group
Environment
O2 Effect
Aerobic
Anaerobic
Obligate Aerobe
Growth
No growth
Required (used for aerobic respiration)
Obligate Anaerobe
No growth
Growth
Toxic
Facultative Anaerobe (Facultative Aerobe)
Growth
Growth
Not required for growth but used when available
Microaerophile
Growth if level is not too high
No growth
Required but at levels below 0.2 atm
Aerotolerant Anaerobe
Growth
Growth
Not required and not used
Examples
Among organisms, almost all animals, most
fungi , and several
bacteria are obligate aerobes.
[2] Examples of obligately aerobic bacteria include
Mycobacterium tuberculosis (
acid-fast ),
[2]
[5]
Bacillus (
Gram-positive ),
[2] and
Nocardia asteroides (
Gram-positive ).
[2]
[6] With the exception of the
yeasts , most
fungi are obligate aerobes.
[1] Also, almost all
algae are obligate aerobes.
[1]
A unique obligate aerobe is
Streptomyces coelicolor which is
gram-positive , soil-dwelling, and belongs to the
phylum
Actinomycetota .
[7] It is unique because the
genome of this obligate aerobe encodes numerous
enzymes with functions that are usually attributed to
anaerobic metabolism in facultatively and strictly
anaerobic bacteria .
[7]
Survival strategies
When obligate aerobes are in a temporarily oxygen-deprived environment, they need survival strategies to avoid death.
[8] Under these conditions,
Mycobacterium smegmatis can quickly switch between
fermentative hydrogen production and hydrogen oxidation with either oxygen or
fumarate reduction depending on the availability of
electron acceptor .
[8] This example is the first time that
hydrogen production has been seen in an obligate aerobe.
[8] It also confirms the
fermentation in a
mycobacterium and is evidence that hydrogen plays a role in survival as well as growth.
[8]
Problems can also arise in oxygen-rich environments, most commonly attributed to
oxidative stress . This occurrence is when there is an imbalance of
free radicals and
antioxidants in the cells of the organism, largely due to
pollution and
radiation in the environment. Obligate aerobes survive this
phenomenon by using the organism's
immune system to correct the imbalance.
[9]
See also
References
^
a
b
c
d
e Prescott LM, Harley JP, Klein DA (1996). Microbiology (3rd ed.). Wm. C. Brown Publishers. pp. 130–131.
ISBN
0-697-29390-4 .
^
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b
c
d
e
f "Obligate aerobe - definition from Biology-Online.org." Biology Online. Biology-Online, n.d. Web. 12 Dec 2009. <
http://www.biology-online.org/dictionary/Obligate_aerobe >
^ Hogg, S. (2005). Essential Microbiology (1st ed.). Wiley. pp. 99–100, 118–148.
ISBN
0-471-49754-1 .
^ WI, Kenneth Todar, Madison.
"Nutrition and Growth of Bacteria" . textbookofbacteriology.net . Retrieved 2021-04-20 . {{
cite web }}
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^ Levinson, W. (2010). Review of Medical Microbiology and Immunology (11th ed.). McGraw-Hill. pp. 150–157.
ISBN
978-0-07-174268-9 .
^ Ryan KJ; Ray CG, eds. (2004). Sherris Medical Microbiology (4th ed.). McGraw Hill. pp. 460–462.
ISBN
0-8385-8529-9 .
^
a
b Fischer, Marco; Alderson, Jesse; van Keulen, Geertje; White, Janet; Sawers, R. GaryYR 2010 (2010).
"The obligate aerobe Streptomyces coelicolor A3(2) synthesizes three active respiratory nitrate reductases" . Microbiology . 156 (10): 3166–3179.
doi :
10.1099/mic.0.042572-0 .
ISSN
1465-2080 .
PMID
20595262 . {{
cite journal }}
: CS1 maint: numeric names: authors list (
link )
^
a
b
c
d Berney, Michael; Greening, Chris; Conrad, Ralf; Jacobs, William R.; Cook, Gregory M. (2014-08-05).
"An obligately aerobic spirillum fermentative hydrogen production to survive reductive stress during hypoxia" . Proceedings of the National Academy of Sciences of the United States of America . 111 (31): 11479–11484.
Bibcode :
2014PNAS..11111479B .
doi :
10.1073/pnas.1407034111 .
ISSN
0027-8424 .
PMC
4128101 .
PMID
25049411 .
^
"What is oxidative stress? Effects on the body and how to reduce" . www.medicalnewstoday.com . 2019-04-03. Retrieved 2021-05-08 .