SURFACE-CHEMISTRY OF THIOBACILLUS-FERROOXIDANS RELEVANT TO ADHESION ON MINERAL SURFACES

Thiobacillus ferrooxidans cells grown on sulfur, pyrite, and chalcopyr ite exhibit greater hydrophobicity than ferrous ion-grown cells. The i soelectric points of sulfur-, pyrite-, and chalcopyrite-grown cells we re observed to be at a pH higher than that for ferrous ion-grown cells . Microbe-mineral interactions result in change in the surface chemist ry of the organism as well as that of the minerals with which it has i nteracted. Sulfur, pyrite, and chalcopyrite after interaction with T. ferrooxidans exhibited a significant shift in their isoelectric points from the initial values exhibited by uninteracted minerals. With anti bodies raised against sulfur-grown T. ferrooxidans, pyrite- and chalco pyrite-grown cells showed immunoreactivity, whereas ferrous ion-grown cells failed to do so. Fourier transform infrared spectroscopy of sulf ur-grown cells suggested that a proteinaceous new cell surface appenda ge synthesized in mineral-grown cells brings about adhesion to the sol id mineral substrates. Such an appendage was found to be absent in fer rous ion-grown cells as it is not required during growth in liquid sub strates.