I am doing experiments with indigenous species isolated from black shale. Surprisingly the consortium containing only bacterial species (without methanogens) produces methane with native as well as with sterilized shale. I am going to repeat the experiment with more accurately sterilized samples (t=100 deg, on 3 following days) but if methane production still persists - either the isolates are not pure but co-cultures with some aero- and/ or thermotolerant Methanosarcinas (more likely) or there is another mechanism for methane production? Many thanks for any suggestions!
SAR11.
http://phys.org/news/2014-07-sar11-oceans-abundant-ability-methane.html
http://www.nature.com/ncomms/2014/140707/ncomms5346/full/ncomms5346.html
http://www.popsci.com/article/science/where-does-oceanic-methane-come-seas-most-abundant-organism
It is an alpha-proteobacterium, not an archaean, as far as I understand.
https://en.wikipedia.org/wiki/Phylogenetic_tree
Trees can also make methane.
http://www.eurekalert.org/pub_releases/2006-01/m-tfm011006.php
Regards,
Joachim
Dear Joachim,
Thank you very much your comprehensive reply with interesting references!
Thus all these organisms could come into consideration, except trees :-)
My own suspicion was from Ryde, U. and Jensen, K.P. (2005) Comparison of chemical properties of iron, cobalt, and nickel porphyrins, corrins, and hydrocorphins. J Porphyrins and Phtalocyanins, 9:
"However, it is still possible that a Ni–CH3 bond is formed in F430 by a heterolytic methyl transfer reaction, provided that the donor is appropriate, e.g. if coenzyme M is protonated. This can be facilitated by the adjacent SO3-group in this coenzyme and by the axial glutamine ligand, which stabilizes the NiIII state. Our results also show that a NiIII–CH3 complex is readily hydrolysed to form a methane molecule and that the NiIII hydrolysis product can oxidize coenzyme B and M to a heterodisulphide in the reaction mechanism of methyl coenzyme M reductase."
Best regards,
Anne.
The question actually have a very simple answer, but one, many people ignore or do not realize: when it comes to metabolic activity, it is veru important to understand tne border of the main catabolic reactions, such as in methanogenic archae and marginal conversions, such as anabolic reactions or side (unspecific) processes. When it comes to biomethane (bio means that it is not thermogenic methane), the only real source are methanogens. No other organisms have the mcr catalyzing the final stage of the methyl group conversion into CH4. There are some evidences that tiny amounts of methane could be releazed as unspecific products from nitrogenase and in clostridia. In you particular case most probably methanogens were present in low numbers but you missed them, which often happen when 16S-rRNA gene is used as a marker. Therefore you must use the methogens-specific functional gene marker - mcrA
Thank you for this thorough explanation! In ongoing experiments already three out of four combinations of isolates show intensive methane gas production (with sterilized shale). I will definitely test all of them with mcrA markers.
Best regards,
Anne Menert.
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