Microbial life in geothermal waters

Abstract

Geothermal waters usually contain many salts, often in varying concentrations. Some of these salts, especially if they consist of oxidizable or reducible ones, can be subject to microbial conversion and/or (bio)precipitation. Microorganisms can oxidize, sometimes even under anoxic conditions, reduced sulfur compounds, iron(II)ions, manganese(II)ions to mention just a few important ones. On the other hand, partially or fully oxidized compounds can be reduced by microorganisms. To be mentioned are sulfur compounds, iron(III)ions, manganese(IV)ions, nitrogen oxides like nitrite and nitrate, and finally bicarbonate and carbonate ions. If organic compounds are present, these may also be oxidized or reduced. A plentiful of microorganisms exists, which are able to perform such metabolism under aerobic or anoxic conditions. All these (bio)processes allow bacteria to grow and proliferate. Consequences may be biocorrosion and biodeterioration. The growth requirements and the biodeterioration mechanisms will be discussed in this review.