Methylotroph
Methylotrophs are a diverse group of microorganisms that can use reduced one-carbon compounds, such as methanol or methane, as the carbon source for their growth; and multi-carbon compounds that contain no carbon-carbon bonds, such as dimethyl ether and dimethylamine.
This group of microorganisms also includes those capable of assimilating reduced one-carbon compounds by way of carbon dioxide using the ribulose bisphosphate pathway.
[1] These organisms should not be confused with methanogens which on the contrary produce methane as a by-product from various one-carbon compounds such as carbon dioxide.
Some methylotrophs can degrade the greenhouse gas methane, and in this case they are called methanotrophs.
The abundance, purity, and low price of methanol compared to commonly used sugars make methylotrophs competent organisms for production of amino acids, vitamins, recombinant proteins, single-cell proteins, co-enzymes and cytochromes.
The key intermediate in methylotrophic metabolism is formaldehyde, which can be diverted to either assimilatory or dissimilatory pathways.
[2][5] Methylotrophs use the electron transport chain to conserve energy produced from the oxidation of
An additional activation step is required in methanotrophic metabolism to allow degradation of chemically-stable methane.
The main metabolic challenge for methylotrophs is the assimilation of single carbon units into biomass.
This is an energy intensive process, which facultative methylotrophs avoid by using a range of larger organic compounds.
Reduction of 6 DPGA by the enzyme glyceraldehyde phosphate dehydrogenase generates 6 molecules of the
[22] Through radio-labelling experiments, it was shown that M. methanica used the ribulose monophosphate (RuMP) pathway.
However, instead of phosphorylating ribulose-5-phosphate, 3 molecules of formaldehyde form a C-C bond through an aldol condensation, producing 3
This produces two molecules of the amino acid serine, the key intermediate of this pathway.
[22][23] Methylotrophic yeast metabolism differs from bacteria primarily on the basis of the enzymes used and the carbon assimilation pathway.
Unlike bacteria which use bacterial MDH, methylotrophic yeasts oxidize methanol in their peroxisomes with a non-specific alcohol oxidase.
[27] As key players in the carbon cycle, methylotrophs work to reduce global warming primarily through the uptake of methane and other greenhouse gases.
Symbiosis between methanogens and methanotrophic bacteria greatly decreases the amount of methane released into the atmosphere.
Marine bacteria are very important to food webs and biogeochemical cycles, particularly in coastal surface waters but also in other key ecosystems such as hydrothermal vents.
There is evidence of widespread and diverse groups of methylotrophs in the ocean that have potential to significantly impact marine and estuarine ecosystems.
[29] One-carbon compounds used as a carbon and energy source by methylotrophs are found throughout the ocean.
Studies have found that methylotrophic capacity varies with the productivity of a system, so the impacts of methylotrophy are likely seasonal.
Because some of the one-carbon compounds used by methylotrophs, such as methanol and TMAO, are produced by phytoplankton, their availability will vary temporally and seasonally depending on phytoplankton blooms, weather events, and other ecosystem inputs.
[33] This means that methylotrophic metabolism is expected to follow similar dynamics, which will then impact biogeochemical cycles and carbon fluxes.
The expansion of omics technologies has accelerated research on the diversity of methylotrophs, their abundance and activity in a variety of environmental niches, and their interspecies interactions.
[35] Further research must be done on these bacteria and the overall effect of bacterial drawdown and transformation of one-carbon compounds in the ocean.
Current evidence points to a potentially substantial role for methylotrophs in the ocean in the cycling of carbon but also potentially in the global nitrogen, sulfur and phosphorus cycles as well as the air-sea flux of carbon compounds, which could have global climate impacts.
Traditional chemical fertilizers supply nutrients not readily available from soil but can have some negative environmental impacts and are costly to produce.
[36] Methylotrophs have high potential as alternative biofertilizers and bioinoculants due to their ability to form mutualistic relationships with several plant species.
[37] Methylotrophic biofertilizers used either alone or together with chemical fertilizers have been shown to increase both crop yield and quality without loss of nutrients.
