Pu-239 Accumulation in E. Coli and P. Putida Grown in Liquid Cultures

Understanding of the behavior and effects of plutonium (Pu) in the environment is an important aspect of developing responsible and effective strategies for remediation and environmental stewardship. This work studies the sorption and uptake of 239Pu by common environmental bacteria, Escherichia coli DH10β and Pseudomonas putida KT-2440. Plutonium was directly incorporated into growth media prior to inoculation (0.12 kBq mL-1), and samples from the liquid cultures of E. coli and P. putida were analyzed over a 15-d growth period through liquid scintillation counting (LSC) of plutonium in cell pellets and cell culture media following centrifugation. To improve its solubility in the liquid cultures, Pu was complexed with citrate prior to inoculation. P. putida cultures were also grown without citrate to examine potential impact of P. putida's ability to use citrate as a food source. The accumulation of Pu in P. putida cells was found to increase both with and without citrate complexation for the first 5 d and then plateau until the end of the study period (15 d). A higher activity concentration of Pu was found in P. putida cells grown with citrate complexation than without. The activity concentration of plutonium in E. coli cells was greater than that in P. putida cells, which may be the result of a stronger complexing agent made by E. coli for the purpose of iron uptake. There are a variety of factors that influence Pu behavior in bacterial systems, and results confirm that even in a simple system, multiple mechanisms are at play.