[Staining of sulfate-reducing bacteria with hexacyanoferrat-compounds (cultural and cytochemical evidence of Fe) (author's transl)]

Hexacyanoferrat-compounds are suitable 1. to indicate the valence of Fe-ions in cultures of desulfuricants (Desulfovibrio spec., Desulfotomaculum) in fluid and solid medium before and after inoculation; 2. stain directly the sulfate-reducing bacteria in presence of Fe-ions and give a colour-reaction of those parts of the cell containing Fe-compounds, e.g. FeS. Therefore they act as a cytochemical indicator system. The chemical base of the reactions are as follows: (1) 4HS + SO42 leads to H2S + 2H2O + OH- H2S leads to H+ + HS- leads to 2H+ + S2- (in the bacteria) (2) FeIII-salt + S2-leads to Fe2S3 leads to 2FeIIS + S 2FeIIS + FeIII(CN6) leads to FeIIIFeII(CN)6 (blue complex-compound).