Fig. 4. Changes in the concentrations of Se⁴⁺, Se^2–, and accumulated Se during incubation after addition of Se⁶⁺ to the coal mine tailings pond sediment. () Sterilized sediment (heat-killed) inoculated with Enterobacter hormaechei; (•) Nonsterilized sediment (live) inoculated with Enterobacter hormaechei; () Nonsterilized sediment (live) without any inoculation; (*) Sterilized sediment (heat-killed) without any inoculation (control). Error bars (±) represent standard error of the mean (n = 3).