Hello,
I am currently testing various methanogenic mediums for growth of methanogenic archaea, but the MM medium keeps failing to create a blackish sediment of Na2S in the solution after the preparations. Instead it creates milk-like haze in the solution with white precipitation on the base.
I am preparing medium in the flask under anoxic condition of CO2/H2 (g) atmosphere with the N2 (g) atmosphere of the other solution.
I have checked the temperature of the solution prior to adition of Na2S if it was cool enough, I have tackled the pH with 0,1 M NaOH solution, or I left it unchanged and I´ve regulated it after completing it.
I´ve been working on the MM medium for some time and I´ve never been adjusting pH or watched the temperature of the solution. I also made a new solution of Na2S and managed to get a new, pure substance, but nothing has changed.
Dis somebody have this issue with MM medium preparation? If yes, please, help me with this step, thus I can continue in use of this medium for cultivation.
Hi Martin Černý:
In principle heavy metal sulfides are insoluble and specifically FeS is black. Sodium and ammonium sulfide are very soluble. I recommend you check for possible heavy metal impurities (Cu, Pb, Fe, Cd, etc.) since the presence of small amounts of those, they could form sediments, but not with Na2S.
Luck and a big hug
Nelson
Hi,
What kind of Methanogen are u trying to cultivate? Mono-culture or a consortium?
Try using different medium, BY, RM02 etc.
Also be sure that the redox potential is low enough in your sample.
Good luck
Nir
Thank you both very much.
To Mr. Farro:
Thank you for your insight to my problem. To this medium, we add Na2S as a main compound and FeSO4 * 7 H2O as a microelement. The black sediment is a desired state.
So from your info, the fact that the sediment isnt forming may be a fact of a bad state of the FeSO4 added to the medium?
Dont you know at which properties of medium (pH, temperature) is reaction Na2S + FeSO4 favourable?
To Dr. Friedman
Thank you very much, I will try the other media too, but I need to solve the problem, because many of our experiments are designed with this medium.
The medium serve as a vessel for both, the consortium for the further isolation of the clear cultures but as well as a medium for the pure microorganisms.
The main one are Methanosarcina sp. but we were trying to cultivate various species from the anaerobic waste sludge, as well as rumen and intestines of various mammals.
I will try to measure and adjust redoxpotential to see what happens.
I am really happy for your help.
Thanks for your kindness.
Best regards.
Martin Černý
Hi Martin Černý:
If the FeS precipitate is desired, then it is better to modify the pH and maintain the constant temperature at which the microorganism develops. Now, since in the hydrolysis reaction:
S2- + H2O ===== HS- + OH-
The presence of S2- is favored by neutral to slightly alkaline pH. You can try, first without adding NaOH, since Na2S gives an alkaline solution by dissolving in water.
Good luck
Nelson
are you using ultrapure (milli Q) water?
Also check if your Na2S 9H2O stock solutiuon is well prepared
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