Evolution of Compositions and Contents of Capsule and Slime EPSs for Adaptation to and Action on Energy Substrates and Heavy Metals by Typical Bioleaching Microorganisms

摘要

Adaption to the energy substrates and heavy metals by bioleaching micoorganisms is the prerequisite for efficient microbe-mineral interaction in bioleaching process. It is known that extracellular polymer substances (EPSs) take an important role in mediating the adaption to and action on energy substrates and heavy metals. This report presents the evolution of compositions and contents of the major components of EPSs of the typical bioleaching microorganisms (Acidithiobacillus ferrooxidans, Leptospirillum ferriphilum, Sulfobacillus thermosulfidooxidans, and Acidianus manzaensis,) exposed to different energy substrates and heavy metal ions. These strains were acclimated firstly to Fe~(2+) substrate, and then on the substrates of elemental sulfur (S°), pyrite and chalcopyrite, respectively. It was found that the major components of capsule and slime EPSs in terms of proteins, polysaccharides and lipids, as well as uronic acids were quite different in contents for the Fe~(2+)-acclimated strains, and they even changed more when the Fe~(2+)-acclimated strains were further acclimated to the other substrates. When exposed to heavy metals, all strains demonstrated much decrease in contents of capsule EPSs, and much increase in slime EPSs contents and the heavy metals were found to be bound to the slime parts. It was for the first time that the EPSs of the bioleaching strains were fractionated into capsule part and slime part. We found the differences in evolution of compositions and contents of the major organic components as well as the inorganic matters of capsule EPSs and slime EPSs when the bioleaching strains were exposed to different energy substrates and heavy metals.