WordNet

restricted to a particular condition of life; "an obligate anaerobe can survive only in the absence of oxygen"
commit in order to fulfill an obligation; "obligate money"
an organism (especially a bacterium) that does not require air or free oxygen to live
caused by law or conscience to follow a certain course; "felt obligated to repay the kindness"; "was obligated to pay off the student loan"

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《受動態で》(道徳上または法律上)〈人〉‘に'義務を負わせる;〈人〉‘に'(・・・する)義務を負わせる《+『名』+『to』 do》
嫌(けん)気性生物(空気・遊離酸素を必要としない細菌類)

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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2016/07/26 11:45:50」(JST)

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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.

Obligate anaerobes are microorganisms killed by normal atmospheric concentrations of oxygen (20.95% O₂).^[1]^[2] Oxygen tolerance varies between species, some capable of surviving in up to 8% oxygen, others losing viability unless the oxygen concentration is less than 0.5%.^[3] An important distinction needs to be made here between the obligate anaerobes and the microaerophiles. Microaerophiles, like the obligate anaerobes, are damaged by normal atmospheric concentrations of oxygen. However, microaerophiles metabolise energy aerobically, and obligate anaerobes metabolise energy anaerobically. Microaerophiles therefore require oxygen (typically 2-10% O₂) for growth. Obligate anaerobes do not.^[1]^[3]^[4]

Oxygen sensitivity

The oxygen sensitivity of obligate anaerobes has been attributed to a combination of factors:

Because molecular oxygen contains two unpaired electrons in its outer orbital, it is readily reduced to superoxide (O−
2) and hydrogen peroxide (H
2O
2) within cells.^[1] Aerobic organisms produce superoxide dismutase and catalase to detoxify these products, but obligate anaerobes produce these enzymes in very small quantities, or not at all.^[1]^[2]^[3]^[5] (The variability in oxygen tolerance of obligate anaerobes (<0.5 to 8% O₂) is thought to reflect the quantity of superoxide dismutase and catalase being produced.^[2]^[3])
Dissolved oxygen increases the redox potential of a solution, and high redox potential inhibits the growth of some obligate anaerobes.^[3]^[5]^[6] For example, methanogens grow at a redox potential lower than -0.3 V.^[6]
Sulfide is an essential component of some enzymes, and molecular oxygen oxidizes this to form disulfide, thus inactivating certain enzymes (e.g. nitrogenase). Organisms may not be able to grow with these essential enzymes deactivated.^[1]^[5]^[6]
Growth may be inhibited due to a lack of reducing equivalents for biosynthesis, because electrons are exhausted in reducing oxygen.^[6]

Energy metabolism

Obligate anaerobes metabolise energy by anaerobic respiration or fermentation. In aerobic respiration, the pyruvate generated from glycolysis is converted to acetyl-CoA. This is then broken down via the TCA cycle and electron transport chain. Anaerobic respiration differs from aerobic respiration in that it uses an electron acceptor other than oxygen in the electron transport chain. Examples of alternative electron acceptors include sulfate, nitrate, iron, manganese, mercury, and carbon monoxide.^[4]

Fermentation differs from anaerobic respiration in that the pyruvate generated from glycolysis is broken down without the involvement of an electron transport chain (i.e. there is no oxidative phosphorylation). Numerous fermentation pathways exist e.g. lactic acid fermentation, mixed acid fermentation, 2-3 butanediol fermentation.^[4]

The energy yield of anaerobic respiration and fermentation (i.e. the number of ATP molecules generated) is less than in aerobic respiration.^[4] This is why facultative anaerobes, which can metabolise energy both aerobically and anaerobically, preferentially metabolise energy aerobically. This is observable when facultative anaerobes are cultured in thioglycollate broth.^[1]

Examples

Examples of obligately anaerobic bacterial genera include Actinomyces, Bacteroides, Clostridium, Fusobacterium, Peptostreptococcus, Porphyromonas, Prevotella, Propionibacterium, and Veillonella. Clostridium species are endospore-forming bacteria, and can survive in atmospheric concentrations of oxygen in this dormant form. The remaining bacteria listed do not form endospores.^[5]

Examples of obligately anaerobic fungal genera include the rumen fungi Neocallimastix, Piromonas, and Sphaeromonas.^[7]

References

^ ^a ^b ^c ^d ^e ^f Prescott LM, Harley JP, Klein DA (1996). Microbiology (3rd ed.). Wm. C. Brown Publishers. pp. 130–131. ISBN 0-697-29390-4.
^ ^a ^b ^c Brooks GF, Carroll KC, Butel JS, Morse SA (2007). Jawetz, Melnick & Adelberg's Medical Microbiology (24th ed.). McGraw Hill. pp. 307–312. ISBN 0-07-128735-3.
^ ^a ^b ^c ^d ^e Ryan KJ; Ray CG, eds. (2004). Sherris Medical Microbiology (4th ed.). McGraw Hill. pp. 309–326, 378–384. ISBN 0-8385-8529-9.
^ ^a ^b ^c ^d Hogg, S. (2005). Essential Microbiology (1st ed.). Wiley. pp. 99–100, 118–148. ISBN 0-471-49754-1.
^ ^a ^b ^c ^d Levinson, W. (2010). Review of Medical Microbiology and Immunology (11th ed.). McGraw-Hill. pp. 91–178. ISBN 978-0-07-174268-9.
^ ^a ^b ^c ^d Kim BH, Gadd GM (2008). Bacterial Physiology and Metabolism.
^ Carlile MJ, Watkinson SC (1994). The Fungi. Academic Press. pp. 33–34. ISBN 0-12-159960-4.

UpToDate Contents

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1. 嫌気菌：ヒトの正常細菌叢における歴史および役割 anaerobic bacteria history and role in normal human flora
2. 嫌気性細菌感染 anaerobic bacterial infections
3. メトロニダゾール：概要 metronidazole an overview
4. 嫌気性感染症における病態生理、臨床的な手がかり、および微生物の回収方法 pathophysiology clinical clues and recovery of organisms in anaerobic infections
5. 破傷風 tetanus

English Journal

Evidence for benzylsuccinate synthase subtypes obtained by using stable isotope tools.

Kümmel S, Kuntze K, Vogt C, Boll M, Heider J, Richnow HH.SourceHelmholtz Centre for Environmental Research-UFZ, Department of Isotope Biogeochemistry, Leipzig, Germany.
Journal of bacteriology.J Bacteriol.2013 Oct;195(20):4660-7. doi: 10.1128/JB.00477-13. Epub 2013 Aug 9.
We studied the benzylsuccinate synthase (Bss) reaction mechanism with respect to the hydrogen-carbon bond cleavage at the methyl group of toluene by using different stable isotope tools. Λ values (slopes of linear regression curves for carbon and hydrogen discrimination) for two-dimensional compoun
PMID 23935041

The second messenger c-di-GMP regulates Clostridium difficile toxin production by controlling expression of sigD.

McKee RW, Mangalea MR, Purcell EB, Borchardt EK, Tamayo R.SourceDepartment of Microbiology and Immunology, University of North Carolina at Chapel Hill, Chapel Hill, NC.
Journal of bacteriology.J Bacteriol.2013 Sep 13. [Epub ahead of print]
The Gram-positive obligate anaerobe Clostridium difficile causes potentially fatal intestinal diseases. How this organism regulates virulence gene expression is poorly understood. In many bacterial species, the second messenger c-di-GMP negatively regulates flagellar motility and, in some cases, vir
PMID 24039264

Diversity of cobalamin riboswitches in the corrinoid-producing organohalide respirer Desulfitobacterium hafniense.

Choudhary PK, Duret A, Rohrbach-Brandt E, Holliger C, Sigel RK, Maillard J.SourceInstitute of Inorganic Chemistry, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland.
Journal of bacteriology.J Bacteriol.2013 Sep 13. [Epub ahead of print]
The strategic adaptation of prokaryotes in polluted niches involves the efficient regulation of their metabolism. The obligate anaerobe and metabolically versatile Desulfitobacterium hafniense reductively dechlorinates halogenated organic compounds (so-called organohalides). Some D. hafniense strain
PMID 24039263

Japanese Journal

血液培養における「嫌気培養ボトル」併用の有効性評価 : 菌検出率と迅速陽性判定の解析から

玉寄美也子,山根誠久,木佐貫京子,河合美夢,仲宗根勇
臨床病理 57(12), 1145-1150, 2009-12-25
NAID 10026337899

SB-1 嫌気性菌の酸素適応機構(微生物の野生の姿に迫る-環境適応とそのメカニズム-, シンポジウム)

川崎信治
日本微生物生態学会講演要旨集 (25), 45, 2009-11-21
NAID 110007520376

Cloning and Expression of the MutM Gene from Obligate Anaerobic Bacterium Desulfovibrio vulgaris (Miyazaki F)

SANADA Hideaki,NAKANISHI Takeshi,INOUE Hideo,KITAMURA Masaya
The journal of biochemistry 145(4), 525-532, 2009-04-01
NAID 10026302275

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