Actinide and metal toxicity to prospective bioremediation bacteria

Abstract

Bacteria may be beneficial for alleviating actinide contaminant migration through processes such as bioaccumulation or metal reduction. However, sites with radioactive contamination often contain multiple additional contaminants, including metals and organic chelators. Bacteria-based bioremediation requires that the microorganism functions in the presence of the target contaminant, as well as other contaminants. Here, we evaluate the toxicity of actinides, metals and chelators to two different bacteria proposed for use in radionuclide bioremediation, Deinococcus radiodurans and Pseudomonas putida, and the toxicity of Pu(VI) to Shewanella putrefaciens. Growth of D. radiodurans was inhibited at metal concentrations ranging from 1.8 microM Cd(II) to 32 mM Fe(III). Growth of P. putida was inhibited at metal concentrations ranging from 50 microM Ni(II) to 240 mM Fe(III). Actinides inhibited growth at mM concentrations: chelated Pu(IV), U(VI) and Np(V) inhibit D. radiodurans growth at 5.2, 2.5 and 2.1 mM respectively. Chelated U(VI) inhibits P. putida growth at 1.7 mM, while 3.6 mM chelated Pu(IV) inhibits growth only slightly. Pu(VI) inhibits S. putrefaciens growth at 6 mM. These results indicate that actinide toxicity is primarily chemical (not radiological), and that radiation resistance does not ensure radionuclide tolerance. This study also shows that Pu is less toxic than U and that actinides are less toxic than other types of metals, which suggests that actinide toxicity will not impede bioremediation using naturally occurring bacteria.

Genes That Enhance the Ecological Fitness of Shewanella oneidensis MR-1 in Sediments Reveal the Value of Antibiotic Resistance

“…MICs for all three cultures were as follows: 200 nM HgCl 2 , 1.25 mM CuSO 4 , 0.8 mM CuCl 2 , 0.2 mM Na 2 HAsO 4 , 0.625 mM NaAsO 2 , and 1 mM CdCl 2 , PbCl 2 , and CoCl 2 . A similar NaAsO 2 MIC was reported for strain MR-1 previously (35); the MICs for CuCl 2 and Na 2 HAsO 4 are similar to values reported for Pseudomonas putida and Deinococcus radiodurans (34). Finally, the MIC for HgCl 2 is a little less than the 500 nM concentration that caused a lag in growth of Sulfolobus solfataricus (36).…”

“…The actual MIC for PbCl 2 was probably lower than we report, as some precipitation was observed. Metal loss due to precipitation may also explain why the MICs for CdCl 2 and CoCl 2 are also high compared to the MICs reported for P. putida and D. radiodurans (34).…”

Biosorption of metal and salt tolerant microbial isolates from a former uranium mining area. Their impact on changes in rare earth element patterns in acid mine drainage

“…U is both chemo-and radiotoxic to biota and causes, amongst others, DNA damage [5]. Copper is known to belong to the group of metals that expose high toxicity towards many bacterial taxa, although essential as cofactor in tiny amounts [30]. The toxic influence of REE on biota has been known for a long time [24].…”

Uranium Bioremediation: Approaches and Challenges

“…Any toxic metal would result in increased lag phase or decreased growth rate which might affect the bioremediation process at the contaminated sites. The concentrations of uranium that inhibited growth of various organisms like Deinococcus radiodurans, Escherichia coli, Pseudomonas putida, Caulobacter crescentus and Shewanella putrefaciens ranged from 500 μM to 3 mM (Hu et al 2005;Ruggiero et al 2005;Wade and DiChristina 2000). The minimum inhibitory concentration (MIC) for bacterial (aerobic, chemoheterotrophic) isolates from subsurface soils of uranium-rich deposits was found to be 4 mM (Kumar et al 2013a).…”