Hi! I am prepping a sulfate reducer (Desulfovibrio sp.) medium (M63 from DSMZ https://mediadive.dsmz.de/medium/63) and I am trying to make sense of the formulation.
So far my understanding is:
K2HPO4 - P / phosphate source
NH4Cl - N source
Na2SO4 - sulfate (e acceptor)
MgSO4 x 7 H2O - sulfate (e acceptor)
CaCl2 x 2 H2O - Ca source / osmotic agent? not sure, but don't care
Yeast extract - carbon source, e donor, everything source :P
Na-thioglycolate - prevents oxygenation of the medium
Ascorbic acid - something similar to thioglycolate?
But most importantly, I do not understand the role of Na-DL-lactate in this medium; I am reading different reports ranging from growth inhibition (huh?) to carbon source ...
The reason I am interested in this, besides understanding what I am doing, is whether I can substitute lactate with a cheaper chemical such as acetate.
Would Na-acetate work the same way?
Thanks a lot for the input!
Kind regards,
Artur
Lactate is the best carbon source for sulphate reducers. Substituting it for acetate can work for some species of SRB but basically you could get minimal growth or no growth. Also, the iron sulphate solution is very important.
Jakub Grzesiak thanks a lot for the input!
So is lactate just the carbon source or/also the e donor? Asking because I am testing H2 consumption by sulfate reducers and am going to provide gaseous H2 as the e donor anyway. So shouldn't the yeast extract cover for the carbon source requirement?
The reason why I omitted FeSo4 was because I thought I would avoid FeS precipitation, i.e. I wanted to make sure I can measure H2S in the gas phase.
Or will I still be able to measure it anyway?
So is the FeSO4 actually necessary for growth specifically as the Fe source? Then the same question applies: doesn't the yeast extract not cover for the iron requirement sufficiently?
Taken together, would you maybe advice to increase the yeast extract content in order to avoid adding FeSO4 (so that I don't precipitate all sulfide)
That's a lot of questions, sorry!
Thanks! : )
Kind regards,
Artur
I did not try to cultivate sulphate reducers on hydrogen, but apparently they need to be adapted (see attached paper). Lactate is both - electron donor and carbon source. Therefore if you want to conduct lithotrophic growth you need to gas the medium with hydrogen and CO2. For sulphide measurement I used the iodometric method - I've taken the liquid with the suspended FeS. Yeast extract is basically there to supply growth factors - vitamins, etc. It does contain some minuscule amounts of glucose (not the best for SRBs). You can try to add some trace elements chelated with EDTA or NTA - they should provide Fe which does not react with sulphides. But I guess you need to find out what conditions work best for your strain.
Best of luck
Jakub
Dear Jakub Grzesiak , thanks a lot for the weath of your input. I think my question is answered more than sufficiently!
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