Chromium(VI) resistance and removal by <Emphasis Type="Italic">Acinetobacter haemolyticus</Emphasis>

The present work highlighted the studies on Cr(VI) reduction by cells of Acinetobacter haemolyticus (A. haemolyticus). The strain tolerated 90 mg Cr(VI) l⁻¹ in LB broth compared to only 30 mg Cr(VI) l⁻¹ in LB agar. From the FTIR analysis, the Cr(III) species formed was also most likely to form complexes with carboxyl, hydroxyl, and amide groups from the bacteria. A TEM study showed the absence of precipitates on the cell wall region of the bacteria. Instead, microprecipitates were observed in the cytoplasmic region of the cells, suggesting the transportation of Cr(VI) into the cells. Intracellular reduction of Cr(VI) was supported by a reductase test using soluble crude cell-free extracts. The specific reductase activity obtained was 0.52 μg Cr(VI) reduced per mg of protein an hour at pH 7.2 and 37°C. Our results indicated that A. haemolyticus can be used as a promising microorganism for Cr(VI) reduction from industrial wastewaters.