Growth-dependent cr(VI) reduction by Alteromonas sp. ORB2 under haloalkaline conditions: toxicity, removal mechanism and effect of heavy metals

This study investigated Cr(VI) reduction under complex haloalkaline conditions by anAlteromonas sp. ORB2 isolated from aerobic granular sludge cultivated from the seawater-microbiome. Optimum growth ofAlteromonas sp. ORB2 was observed under haloalkaline conditions at 3.5 –9.5% NaCl and pH 7–11. The bacterial growth in normal culture conditions (3.5% NaCl; pH 7.6) was not inhibited by 100 mg/l Cr(VI)/ As(V)/ Pb(II), 50 mg/l Cu(II) or 5 mg/l Cd(II). Near complete reduction of 100 mg/l Cr(VI) was achieved within 24 h at 3.5–7.5% NaCl and pH 8–11. Cr(VI) re duction byAlteromonassp. ORB2 was not inhibited by 100  mg/L As(V), 100 mg/L Pb(II), 50 mg/L Cu(II) or 5 mg/L Cd(II). The bacterial cells grew in the medium with 100 mg/l Cr(VI) contained lower esterase activity and higher reactive oxygen species levels indicating toxicity and oxidative stress. In-spite of toxicity, the cells grew and reduced 100  mg/l Cr(VI) completely within 24 h. Cr(VI) removal from the medium was driven by bacterial reduction to Cr(III) which remained in the complex medium. Cr(VI) reduction was strongly linked to aerobic growth ofAlteromonas sp. The Cr(VI) reductase activity of cytosolic protein fraction was pronounced by supplementing with NADPH in vitro assays. This study demonstrated a growth-dependent aerobic Cr(VI) reduction byAlteromonas sp. ORB2 under complex haloalkaline conditions akin to wastewaters.
Source: World Journal of Microbiology and Biotechnology - Category: Microbiology Source Type: research