Relationship among the secretion of extracellular polymeric substances, heat resistance, and bioleaching ability of Metallosphaera sedula

This paper describes the investigation of the secretion of extracellular polymeric substances (EPS) by an extremely thermoacidophilic archaea, Metallosphaera sedula (M. sedula), during the bioleaching of pyrite under different temperatures and discusses the relationship among the EPS secretion, its heat resistance, and its ability to bioleach pyrite. The investigation results indicate that the amount of extracellular proteins is significantly higher than the amount of extracellular polysaccharides in the extracted EPS whether free cells or attached cells; these results are quite different from the behavior of mesophilic Acidithiobacillus ferrooxidans. Although the growth of M. sedula is inhibited at 80℃, the bioleaching ability of M. sedula is only slightly lower than that at the optimum growth temperature of 72℃ because of the heat resistance mechanism based on EPS secretion. The secretion of more extracellular proteins is an important heat resistance mechanism of M. sedula.