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Original: "Methylotroph"

General microbiology

Methylotrophs are a diverse group, including both Gram-negative and Gram-positive genera. None of them make resting structures like exospores or cysts and none of them have the complex intracellular membrane systems that characterize methanotrophs growing on methane

There are two sub groups:

  1. obligate methylotrophs.
  2. facultative methylotrophs.
Obligate methylotrophs

A single obligate methylotroph (methylophilus) is known. It is Gram-negative, polarly flagellated rod capable of rapid growth with methanol. Some strains can also utilize formaldehyde or methylamines. Carbon is assimilated via the ribulose mono phosphate pathway.

Facultative methylotrophs

It is relatively widely distributed trait among heterotrophic bacteria. It may also be common among chemoautotrophs: several thiobacilli and nitrifying bacteria can drive CO2 assimilation via the Calvin-Benson cycle by formate oxidation.

Edit: "Methylotroph"


Metabolism

The key intermediate behind methylotrophic metabolism is formaldehyde which can be diverted to either catabolism or anabolism.[1] Methylotrophs arrive at formaldehyde through oxidation of methanol and/or methane. Methane oxidation requires the enzyme methane monooxygenase (MMO)[2][3]. Methylotrophs with this enzyme are given the name methanotrophs. The oxidation of methane (or methanol) can be assimilatory or dissimilatory in nature (See Figure 1). If dissimilatory, the formaldehyde product will be oxidized completely into to produce reductant and energy[4][5]. If assimilatory, formaldehyde is used to synthesize a 3-Carbon () compound used for the production of biomass[1][6]. Many methylotrophs may use multi-carbon compounds for anabolism, limiting their use of formaldehyde to dissimilatory processes, while methanotrophs are generally limited to only metabolism.

Compounds known to support methylotrophic metabolism[6][7][8][9][10]
Single Carbon Compounds Chemical Formula Multi-Carbon Compounds Chemical Formula
Carbon monoxide Dimethyl ether
Formaldehyde Dimethylamine
Formamide Dimethyl sulfide
Formic acid Tetramethylammonium
Methane Trimethylamine
Methanol Trimethylamine N-oxide
Methylamine Trimethylsuphonium
Methyl halide
File:Common methylotrophic metabolic pathways.jpg
General steps of methylotrophic metabolism displaying 4 known assimilatory methylotrophic pathways. The general catabolic pathway is also shown. Q denotes a membrane-bound quinone. Methane monooxygenase (MMO) and Formate dehydrogenase (FDH) may be membrane-associated or cytoplasmic while Methanol dehydrogenase (MDH) and Formaldehyde dehydrogenase (FALDH) are always membrane-associated.

Catabolism

Methylotrophs use the electron transport chain to conserve the energy from the oxidation steps. For methanotrophs, an activation step is required to make chemically-stable methane amenable for further degradation. This oxidation to methanol is catalyzed by MMO which incorporates 1 oxygen atom into methane and reduces the other oxygen atom to water, which requires 2 equivalents of reducing power[3][4]. Methanol is then oxidized to formaldehyde through the action of either methanol dehydrogenase (MDH) in bacteria[11] or a non-specific alcohol oxidase in yeast[12]. Electrons from methanol oxidation are passed to a membrane-associated quinone of the electron transport chain to produce [13].

In dissimilatory processes, formaldehyde is completely oxidized to and released. Formaldehyde is oxidized to formate via the action of Formaldehyde dehydrogenase (FALDH) which directly provide electrons to a membrane associated quinone of the electron transport chain, usually cytochrome b or c[1][4]. In the case of associated dehydrogenases, is produced[6]. Formate is oxidized to by cytoplasmic or membrane-bound Formate dehydrogenase (FDH) which produces [14]. 

Anabolism

The main metabolic challenge for methylotrophs is the assimilation of single carbon units into biomass. Through de novo synthesis, Methylotrophs must form carbon-carbon bonds with each 1-Carbon () molecule. This is an energy intensive process which facultative methylotrophs avoid by using a range of larger organic compounds[15]. However, obligate methylotrophs must assimilate molecules. There are four distinct assimilation pathways with the common theme of generating one molecule [1]. Bacteria use three of these pathways[6][10] while Fungi use one[16]. All four pathways use multi-carbon intermediates to incorporate the 3 molecules into, then perform a cleavage step which creates a new molecule for biomass. The remaining intermediates are rearranged to regenerate the original multi-carbon intermediates.

CodeSwitch (talk) 14:55, 2 November 2017 (UTC)

CodeSwitch (talk) 01:47, 19 November 2017 (UTC)

  1. ^ a b c d Yurimoto, Hiroya; Kato, Nobuo; Sakai, Yasuyoshi (2005-01-01). "Assimilation, dissimilation, and detoxification of formaldehyde, a central metabolic intermediate of methylotrophic metabolism". The Chemical Record. 5 (6): 367–375. doi:10.1002/tcr.20056. ISSN 1528-0691.
  2. ^ Nguyen, Ngoc-Loi; Yu, Woon-Jong; Yang, Hye-Young; Kim, Jong-Geol; Jung, Man-Young; Park, Soo-Je; Roh, Seong-Woon; Rhee, Sung-Keun (28 September 2017). "A novel methanotroph in the genus Methylomonas that contains a distinct clade of soluble methane monooxygenase". Journal of Microbiology. 55 (10): 775–782. doi:10.1007/s12275-017-7317-3.
  3. ^ a b Ross, Matthew O.; Rosenzweig, Amy C. (2017-04-01). "A tale of two methane monooxygenases". JBIC Journal of Biological Inorganic Chemistry. 22 (2–3): 307–319. doi:10.1007/s00775-016-1419-y. ISSN 0949-8257.
  4. ^ a b c Hanson, R. S.; Hanson, T. E. (1996-06-01). "Methanotrophic bacteria". Microbiological Reviews. 60 (2): 439–471. ISSN 1092-2172. PMID 8801441.
  5. ^ Vorholt, Julia A. (2002-10-01). "Cofactor-dependent pathways of formaldehyde oxidation in methylotrophic bacteria". Archives of Microbiology. 178 (4): 239–249. doi:10.1007/s00203-002-0450-2. ISSN 0302-8933.
  6. ^ a b c d J Colby; H Dalton; Whittenbury, and R. (1979). "Biological and Biochemical Aspects of Microbial Growth on C1 Compounds". Annual Review of Microbiology. 33 (1): 481–517. doi:10.1146/annurev.mi.33.100179.002405. PMID 386931.
  7. ^ Oremland, Ronald S.; Kiene, Ronald P.; Mathrani, Indra; Whiticar, Michael J.; Boone, David R. (1989-04-01). "Description of an Estuarine Methylotrophic Methanogen Which Grows on Dimethyl Sulfide". Applied and Environmental Microbiology. 55 (4): 994–1002. ISSN 0099-2240. PMID 16347900.
  8. ^ Holmes, Andrew J.; Kelly, D. P.; Baker, Simon C.; Thompson, A. S.; Marco, Paolo De; Kenna, Elizabeth M.; Murrell, J. Colin (1997-01-01). "Methylosulfonomonas methylovora gen. nov., sp. nov., and Marinosulfonomonas methylotropha gen. nov., sp. nov.: novel methylotrophs able to grow on methanesulfonic acid". Archives of Microbiology. 167 (1): 46–53. doi:10.1007/s002030050415. ISSN 0302-8933.
  9. ^ Kelly, Don P.; Baker, Simon C.; Trickett, Jim; Davey, Margaret; Murrell, J. Colin (1994). "Methanesulphonate utilization by a novel methylotrophic bacterium involves an unusual monooxygenase". Microbiology. 140 (6): 1419–1426. doi:10.1099/00221287-140-6-1419.{{cite journal}}: CS1 maint: unflagged free DOI (link)
  10. ^ a b Firsova, Julia; Doronina, Nina; Lang, Elke; Spröer, Cathrin; Vuilleumier, Stéphane; Trotsenko, Yuri. "Ancylobacter dichloromethanicus sp. nov. – a new aerobic facultatively methylotrophic bacterium utilizing dichloromethane". Systematic and Applied Microbiology. 32 (4): 227–232. doi:10.1016/j.syapm.2009.02.002.
  11. ^ Duine, J.a.; Frank, J.; Berkhout, M.p.j. (1984-03-26). "NAD-dependent, PQQ-containing methanol dehydrogenase: a bacterial dehydrogenase in a multienzyme complex". FEBS Letters. 168 (2): 217–221. doi:10.1016/0014-5793(84)80249-5. ISSN 1873-3468.
  12. ^ Murray, William D.; Duff, Sheldon J. B.; Lanthier, Patricia H. (1989-11-01). "Induction and stability of alcohol oxidase in the methylotrophic yeast Pichia pastoris". Applied Microbiology and Biotechnology. 32 (1): 95–100. doi:10.1007/BF00164829. ISSN 0175-7598.
  13. ^ Verseveld, H. W. Van; Stouthamer, A. H. (1978-07-01). "Electron-transport chain and coupled oxidative phosphorylation in methanol-grown Paracoccus denitrificans". Archives of Microbiology. 118 (1): 13–20. doi:10.1007/BF00406068. ISSN 0302-8933.
  14. ^ Chistoserdova, Ludmila; Crowther, Gregory J.; Vorholt, Julia A.; Skovran, Elizabeth; Portais, Jean-Charles; Lidstrom, Mary E. (2007-12-15). "Identification of a Fourth Formate Dehydrogenase in Methylobacterium extorquens AM1 and Confirmation of the Essential Role of Formate Oxidation in Methylotrophy". Journal of Bacteriology. 189 (24): 9076–9081. doi:10.1128/jb.01229-07. ISSN 0021-9193. PMID 17921299.
  15. ^ Reed, William M.; Dugan, Patrick R. (1987). "Isolation and Characterization of the Facultative Methylotroph Mycobacterium ID-Y". Microbiology. 133 (5): 1389–1395. doi:10.1099/00221287-133-5-1389.{{cite journal}}: CS1 maint: unflagged free DOI (link)
  16. ^ van der Klei, Ida J.; Yurimoto, Hiroya; Sakai, Yasuyoshi; Veenhuis, Marten. "The significance of peroxisomes in methanol metabolism in methylotrophic yeast". Biochimica et Biophysica Acta (BBA) - Molecular Cell Research. 1763 (12): 1453–1462. doi:10.1016/j.bbamcr.2006.07.016.
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