Is the growth a fungal isolate on the N-Free medium sufficient to conclude that the isolate is a nitrogen-fixing fungi?
Aspergillus could be an exception , otherwise all AMs are so aggressive nitrogen fixers, lichens , such exceptional cases could be isolated and debated by and large , how fungi participates in nitrogen fixation...
Hello Professor,
your answer interests me because I am confronted with the same case.
I isolate a strain of aspergillus which can grow on N free medium, but no article reports that fungal strain possesses this faculty.
I would like to know if there is another easy test to confirm this capacity of fixation of atmospheric nitrogen.
Thank you in advance for any help you can provide
Salam
It is known that the ability to fix atmospheric nitrogen is the fonction of certain groups of specialized prokaryotes
(1) the free or non-symbiotic fixatives (ex. Azotobacter, Azomonas, Xanthobacter & Beijerinckia...)
.
(2) the associatif non-symbiotic fixatives (ex. Azospirillum which juxtapose the roots of Poaceae) and
(3) the symbiotic fixatives (the so-called RHIZOBIA : Rhizobium, Bradyrhizobium and the ACTINORHIZA : Frankia)
So concerning Fungi, despite having complicated metabolic devices but the ability to fix diatomic nitrogen is a little known function in these organisms (ex Pleurotus spp.)
The question that arises: does the nitrogenase complex exist or not in these groups? It is important to remember that this function is generally dependent on the biological system, which for example in the case of Pleurotus is apparently associative with diazotrophs, but it has not been fully elucidated especially if you put into consideration that the enzymatic reduction of Hydrogen ions is an extremely energy demanding process ??!!
For the ARA method, it is possible to reveal the reducing function of an enzyme or enzymatic complex to simulate for example the nitrogenase
And if you try your experiments under anaerobic conditions ? As well as the effect of phosphorus (as a source of biological energy)??
Somehow, there is no convincing report where a non-prokaryotic organism has been credited for N-fixing ability. If your strain is able to grow on N free medium, I recommend the following steps:
1. See the inoculation condition and re-check if traces of nitrogen source is going in medium/glassware by some practical error.
2. Perform ARA, with sealed tubes having growth of your organism.
3. Use heavy Nitrogen, and find traces of it in biomolecules of your isolate.
(just growth on medium can not be considered as confirmatory)
Azul,
i'd like to suggest a diferent type of approach (Inverse Methodology), which is to query the NCBI or PDB database and look for the enzymes involved in azote fixation in relation with the isolated fungus.
Good luck.
There is not evidence scientific that demostrates such ability
Salam, tanmirt ik a Rafik
Biological fixation of nitrogen is specific for a prokaryotic group (bacteria and archaea). No eukaryote (plant and fungi) is able to convert N2 into active nitrogen species (NH3).
In these microorganisms, the fixation of N2 is ensured by an enzymatic complex called nitrogenase. This complex is composed of 2 metallo-enzymes.
For more information, see this article:
"State of the art in eukaryotic nitrogenase engineering" Article State of the Art in Eukaryotic Nitrogenase Engineering
Please have a look at the following RG link.
Article Potential for Nitrogen Fixation in the Fungus-Growing Termit...
Hi,
There are recent reports which say that fungus may contain endophytic N2 fixing bacteria which may fix nitrogen. So I think in your case it should be tested.
Check the link below:
https://www.eurekalert.org/pub_releases/2019-11/asop-iwf112019.php?fbclid=IwAR0eDga36-B0M-g3anCJ8JLXmDgRt5155kScuPoeTUJ1G8xlrcCbLPYTO80#.Xdg_9SRsVMY.facebook
Hope that helps.
Best,
SS
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