Filter-sterilized aqueous solutions of sodium (Na) selenate and
Na-selenite (Sigma–Aldrich, Australia) were added to selenium free
MRS broth to a final volume of 4 ml in sterilized Hungate
tubes. A total of 4 concentration treatments plus a control treatment
were performed in duplicates, and the nominal concentrations
used were 1, 2, 3, 4 and 5 lg selenium/ml in selenate or
selenite forms. The growth and viability of bacteria were evaluated
by counting the living cells using MRS agar media as described
previously.