The EPS of Acidithiobacillus ferrooxidans--a model for structure-function relationships of attached bacteria and their physiology
Gehrke, T.; Hallmann, R.; Kinzler, K.; Sand, W.
Water Science and Technology a Journal of the International Association on Water Pollution Research 43(6): 159-167
2001
ISSN/ISBN: 0273-1223 PMID: 11381962 Document Number: 531433
To dissolve pyrite or sulphur, leaching bacteria like Acidithiobacillus ferrooxidans attach to these substrata by extracellular polymeric substances (specifically, lipopolysaccharides). The primary attachment to pyrite at pH 2 is mediated by exopolymer-complexed iron(III) ions in an electrostatic interaction with the negatively charged pyrite surface. Cells grown on sulphur exhibit a different composition of the extracellular lipopolysaccharides, namely with increased hydrophobic properties, and do not attach to pyrite. Thus, the cells adapt the chemical composition of their exopolymers to the substrate/substratum. It is concluded that the mechanism of bacterial pyrite oxidation is basically indirect. The actual corrosive agents are iron(III) ions. Preliminary data indicate that active strains complex more iron(III) ions in their EPS than less active ones. Obviously, the exopolymeric layer comprises a reaction space for the regeneration of these ions by the activity of the iron oxidising bacteria.