MINIMAL SALT MEDIUM - DIESEL DEGRADATION (Oct/21/2010 )

HI everybody.
I have the following question.
I am growing by bacteria in MSM of the following composition:
Minimum salts medium (MSM) was a mixture of solutions A, B and C.
Solution A contained (per 400 ml) 16 g of NH4NO3, 18.8 g of KH2PO4, 0.476 g of Na2HPO4, and 0.04 g of CaCl2 2H2O. This solution was adjusted to pH 7.0 with NaOH.
Solution B contained (per 400 ml) 4 g of MgSO4 7H2O, and 0.04 g of MnSO4 7H2O.
Solution C contained (per 400 ml) 0.03 g of FeSO4 7H2O.
10 ml of solution A mixed with 60 ml of distilled water, 10 ml of solution B, and 20 ml of solution C were separately autoclaved at 121C for 20 min, and then they were mixed.
I observe that after autoclaving and mixing a red sedimentation occurs.
This medium is used for growing bacteria with diesel and monitoring the degradation rates.
Also this sedimentation affects my O.D measurements.
I am waiting for your remarks


Gorens

Do you see the sedimentation right after autoclaving (not mixed) or after you mixed them?

It could be some sort of percipitationreaction.

pito on Thu Oct 21 10:49:58 2010 said:

Just after I autoclave solution C ( most probably due to the iron content).
Do you have any recommendations for alternative Minimal mediums for the described purpose?

Regards,

gorens

Right FeSo4 precipitates when autoclaved. We usually filter-sterilise it (or a stock solution which can be pipetted directly into the cooled agar medium.