Viability and Growth of Secondary Cultures of Shewanella Oneidensis MR-1 in Tryptic Soy Broth and Glucose-Based Minimal Media

Radioiodine-129 (I129), in the form of iodate, organo-iodide, and iodide, is one of the major groundwater contaminants at the Hanford Site in Washington State due to the leakage from nuclear waste storage tanks. However, Shewanella oneidensis MR-1 is a bacteria strain that can reduce silver and uranium and has shown potential to act as a bioremediation agent that converts the iodate to a less harmful, more easily remediated iodide compound.

To maximize S. oneidensis’s growth and take advantage of its reductive capabilities, we hypothesized that the planktonic cultures needed to be initially grown in Tryptic Soy Broth (TSB) and then resuspended in glucose-based minimal media (GM9) for the bioremediation of iodate. We also proposed that after 24 hours, the bacteria cells in GM9 would remain viable enough to perform further iodate reduction.

UV Spectrophotometry was used to monitor the growth of S. oneidensis over several 24-hour time points. The experimental results proved that the growth in TSB is significantly greater than the growth in GM9. This emphasizes the need for an initial cultivation in TSB to have sufficient bacteria cells for the bioremediation in GM9. Additionally, the results showed that the bacteria cells remain viable in GM9. Further work is in progress to investigate the bacteria’s viability beyond 24 hours.

Success of this overall project will result in an established methodology for the investigation of planktonic S. oneidensis cells as a bioremediation agent against iodate. This may then be scaled to design novel microbial bioreactor systems for contaminated groundwater treatment.

Funder Acknowledgment(s): This study was supported by an NSF DEB Award#1832140 to Dr. Patrick Ymele-Leki.