FIG. 3.

Solubilization of CuO, Fe₂O₃, MnO₂, metallic zinc (Zn), and rock phosphate (Rp) by cell-free culture filtrates of T-22 grown in SY medium (SYT) in comparison with noninoculated medium filtrates (SY). Filtrates were either untreated, autoclaved (121°C for 20 min), or digested with protease K (50 μg/ml for 4 h at 37°C). Inoculated SY medium not supplemented with any of the above minerals provided the basic levels of the various elements in culture filtrates. Error bars indicate standard deviations of three replicate determinations.