FIG. 3.

XAS spectra of Tc(VII) (pertechnetate anion), Tc(IV) reduced via biogenic magnetite (in good agreement with the reference spectrum for TcO₂ [1]), and Tc reduced via a direct hydrogen-dependent mechanism. A spectrum modelled by assuming 60% reduced Tc(IV) and 40% Tc(VII) is also included and is in good agreement with the spectrum obtained from the cultures containing Tc reduced by the direct, hydrogen-dependent mechanism [at a similar ratio of 60% Tc(IV) to 40% residual Tc(VII) as determined independently using a phosphorimager-based technique (19)].