COMPARING THE CAPACITY OF BACILLUS SUBTILIS, MICROCOCCUS LUTEUS, AND PSEUDOMONAS AERUGINOSA TO REDUCE CHROMIUM (VI) TO CHROMIUM (III)

Chromium, a common component in industrial manufacturing, can cause serious environmental problems when released into the environment, affecting soils, groundwater, and the atmosphere. Chromium takes either the hexavalent (Cr⁶⁺) form or the trivalent form (Cr³⁺) when released into the environment, with Cr⁶⁺ exhibiting higher solubility, mobility, and toxicity than Cr³⁺. In this study, we evaluated the capability of three different aerobic bacteria, Bacillus subtilis, Micrococcus luteus, and Pseudomonas aeruginosa, to convert the mobile, soluble, and toxic Cr⁶⁺ to Cr³⁺, which poses much less of a threat to the environment and human health. In our study, the organisms had no previous exposure to chromium, indicating their availability for use without the need to acclimate them to a chromium-rich environment before deployment.

The strains of bacteria are standardized American Type Culture Collection (ATCC) strains acquired from a local hospital. These organisms will be grown on blood agar plates (BAP), and 0.25 mL of a 0.5 MacFarland standard will be transferred to 25 mL LB broth after 24 hours of incubation. A 10 mM K2CrO4 stock solution will be diluted to achieve a final concentration of 1 uM, 50 uM, or 100 uM in the reduction experiments, and these concentrations will be added to the inoculated LB broth flasks. After an additional 24-hour incubation, the concentrations of Cr⁶⁺ will be determined using a UV-VIS spectrometer using prepared standards as a baseline reference.

Preliminary runs indicated that all three bacterial strains reduced Cr⁶⁺, and that B. subtilis was the most effective reducer, followed by M. luteus and P. aeruginosa. These aerobic bacteria are commonly encountered in the environment and our preliminary results indicate that native bacteria are a potential remediation tool for chromium impacted areas.