Differential utilization and speciation transformation of orthorhombic α-S8 and amorphous μ-S by substrate-acclimated mesophilic Acidithiobacillus ferrooxidans

The utilization and speciation transformation of α-S8 and μ-S by the typical mesophilic acidophilic strain Acidithiobacillus ferrooxidans ATCC 23270 were investigated. A. ferrooxidans cells first acclimated to the energy source α-S8 or μ-S, respectively. The results of cell growth and sulfur oxidation behavior showed that the strain grown on α-S8 entered slowly (about 1 d later) into the exponential phase, while grew faster in the exponential phase and attained higher maximal cell density and lower pH value than that on μ-S. After bio-corrosion, both of the two sulfur samples were evidently eroded and modified by A. ferrooxidans cells. After growth of A. ferrooxidans, the surface composition of amorphous μ-S became 63.1% μ-S and 36.9% α-S8, and that of orthorhombic α-S8 became 68.3% α-S8 and 31.7% μ-S, while the surface compositions of α-S8 and μ-S in sterile experiment were not changed, indicating that these two elemental sulfur species can be interconverted by A. ferrooxidans.