Syntrophy: An overview

  • It’s a situation in which two different organism works to degrade one substance and also conserve energy by doing this.
  • This degradation cannot be done individually.
  • Most syntrophic reaction are secondary fermentation.
  • In this the organism format the fermentation product of other anaerobes.

Reaction details:-

  • The centre of almost all syntrophic reaction is hydrogen production by one partner which is consumed by the other partner.
  • The H2 consumer can be of any number and variety of organism as example denitrifying bacteria, ferric ion reducing bacteria, sulfate reducing bacteria, acetogens, methanogen.

Example 1

  • This fund of syntrophic reaction is called as instaspecies hydrogen transfer for hydrogen metabolism is the main in the process.
  • In this reaction of ethanol fermentation to acetate acid production of methane in the process takes place.
  • Ethanol fermentor do a reaction as example unfavourable in the standard free energy change.
  • The hydrogen produced by the ethanol fermentor can be used as an electron donor for methanogenesis reaction by methanogens.
  • But if the two reaction are summed or put together the overall reaction is exergonic and supplies the energy needed for the growth of both partners into the syntrophic relationship.

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Types of reactions

Endergonic reaction:-

  • It is also known as unfavourable reaction for a non spontaneous reaction in which standard change in free energy is positive and energy is absorbed.
  • In layman’s term the total amount of energy is a loss it takes more energy to start a reaction then what you get out of it so the total energy is a negative result .
  • This reaction can be achieved if they are added with a exergonic like stability, increasing negative changes in free energy process.
  • Endergonic reaction can be coupled with another reaction which is strongly exergonic through shared intermediate.
  • This is often how biological reaction process as X+Y=XY
  • It maybe too endergonic to ok yeah but it may be possible by coupling into strongly exergonic reaction like the decomposition of ATP into ADP and Pi ions.



XP+ Y—-> XY+Pi

  • In this reaction the ATP decomposition supply free energy to make an endergonic reaction occurs it is so common in cell biochemistry that ATP is often called as the universal energy currency of all living organism.

Exergonic reaction:-

  • It is occur spontaneously which release free energy.
  • They require small input of energy from outside source to cause the reaction.
  • Activation energy is required high for endergonic.
  • The outside energy is called activation energy.
  • And many reaction in the cell are endergonic.


  • Another example of entropy is oxidation of butyrate to acetate + hydrogen by the fatty acid oxidizing syntroph syntrophomonas.
  • Butyrate + 2 H2O–>2 acetate + H+ + 2H2
  • The free energy changes in this reaction is highly unfavourable.
  • In a pure culture centrophomonas will not grow on butyrate but if H2 is consumed by a partner then introphomonas as well grow in co culture with the H2 consumer.
  • The energetics of the oxidation of ethanol or butyrate to acetate + H2 is a reaction that is endergonic.
  • But if the concentration of H2 is kept extremely low by consumption by the partner then delta G for the oxidation of butyrate by cyntrophomonas yield -18 kj/ mol.

Characteristics of syntrophs:-

  • Syntrophs use the fermentation product of primary fermentor and release a key product.
  • For methanogens acetogens and other H2 consumers and syntrophy is characteristics of anoxic process in which:-
  • The energy available is only very small.
  • one or more product is continuously removed.
  • The organism are highly specialised to explanting energetically at a very limited amount in this reaction.

 Syntrophy and methanogenesis:-

  • to convert most organic compound to methane the methanogenesis must therefore team of with partner organism that can supply them with methanogenes materials. This is the work of the syntrophs.

Anoxic decomposition and syntrophy:-

  • Syntrophy is a process in which two or more organisms co-operate in the anaerobic degradation of organic compound.
  • Polysaccharides protein lipids and nucleic acid from dead organism normally goes naturally into some anoxic habitats.
  • Then they go for hydrolysis and the resultant monomers are excellent electron donors for energy metabolism.
  • Breakdown of a typical polysaccharide like cellulose of cellulolytic bacteria start hydrolysing cellulose in to cellobiose and then in to glucose.
  • The glucose is fermented by primary fermentor to short chain fatty acid and to alcohols H2 and CO2
  • H2 is quickly removed by methanogens along with acetate.
  • But directly this organic carbons can’t be directly utilised by methanogens.
  • The catabolism of this compound requires syntrophy and the important fermentative acetic of syntrophic bacteria.

Role of the syntrophs:-

  • The main bacteria in the conversion of organic material to methane are syntrophs.
  • These are secondary fermentors.
  • Syntrophs ferments the product of primary fermentors producing primary hydrogen CO2 and acetate.


Syntrophomonas wolfii:-

  • Oxidizes C4 to c8 fatty acids yielding acetate CO2 and H2 .
  • Some syntrophomonas use fatty acid upto c18 in length including some unsaturated fatty acid.

Syntrophobactor walinni:-

  • It is specialise in propionate C3 fermentation building acetate, CO2 and H2