Chromate reduction by Bacillus megaterium TKW3 isolated from marine sediments

Summary

Bacillus megaterium strain TKW3 was isolated from multiple-metal-contaminated marine sediments of Tokwawan, Hong Kong SAR. This facultative aerobe utilized arabinose, mannitol, N-acetylglucosamine, maltose, caprate, citrate, butyrate or lactate as the sole source of carbon and energy for growth.B. megaterium TKW3 reduced highly toxic and soluble Cr⁶⁺ (as CrO ²⁻₄ ) into almost non-toxic and insoluble Cr³⁺ under aerobic conditions. Complete reduction of 0.20 mM Cr⁶⁺ by B. megaterium TKW3 was achieved within 360 h. Initial Cr⁶⁺ concentration below 0.90 mM or inoculum less than 10⁷ cells ml⁻¹ did not have significant effect on ⁶⁺ reduction, while the residue Cr⁶⁺ concentration was the lowest at 10⁷ cells ml⁻¹. Cr⁶⁺ reduction by this strain was inhibited by high levels of NaCl (55%). B. megaterium TKW3 was also resistant to other oxyanions including 0.34 mM Cr₂O ²⁻₇ 0.32 mM AsO ³⁻₄ , 0.58 mM SeO ²⁻₃ and 0.53 mM SeO ²⁻₄ , and reduced soluble Se⁴⁺ (as SeO ²⁻₃ ) to insoluble red amorphous Se⁰. B. megaterium TKW3 might have potential application in bioremediation of Cr-laden sediments associated with other oxyanions.