Bulk and surface characterization of crystalline and plastic sulphur oxidized by two Thiobacillus species

This work studies the surface interaction between Thiobacillus ferrooxidans and Thiobacillus thiooxidans with crystalline and plastic elemental sulphu r. The interaction mechanisms were analysed by fractal geometry which descr ibes textural modifications of the substrate caused by bacterial action. Th e results demonstrated that the bacteria are able to produce two different effects depending on the substrates. Only surface smoothing (decrease on fr actal dimension values) was detected on crystalline sulphur (this effect be ing stronger with T. ferrooxidans than with T. thiooxidans), but, perforati on of the bulk was also observed in plastic sulphur (C) 1999 Elsevier Scien ce Ltd. All rights reserved.