Autotrophic microorganisms in water

In terms of obtaining drinking and process water, it is not only saprophytic bacteria which are of significance. In addition the so-called iron and manganese bacteria and sulphur bacteria can be of special importance as autotrophic bacteria. 

Iron and manganese bacteria live primarily in waters containing iron and manganese. They oxidize bivalent iron and manganese compounds in these waters to higher levels of oxidation. For this purpose these bacteria need oxygen, albeit only in very small quantities. 

As a rule metallic iron is not attacked directly but, instead, only ferrous ions are utilised and for this their concentration must lie between 0.2 and 12 mg/1. Cultures stop growing when the iron concentration is more than 14 

Presence of ferrous ions or manganese (II) ions in the necessary concen- 

Redox potential and pH in the growth field for iron and manganese bacte- 

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