322 TRANSURANIC ELEMENTS IN THE ENVIRONMENT 



TABLE 6 Distribution of Plutonium in Mixed Microbial Cultures* Continuously 

 Exposed to Plutonium and Grown on Different Carbon Sources 



*Cultures were not replicated. Analytical precision was < ± 10% (1 a). Plutonium present in 

 cell washes before homogenization is not included. 



sets of culture conditions, there was a high concentration of plutonium bound to the cell 

 wall and membrane fractions and thus was insoluble. As these materials are degraded by 

 lytic enzymes, e.g., proteases and chitinases, soluble plutonium compounds may be 

 formed. 



Preliminary characterization, using gel permeation chromatography, of the mixed 

 culture of fungi isolated from soil and grown in sugars indicated that the plutonium form 

 was altered during fungal growth (Fig. 7). The exocellular and intracellular soluble 

 fractions obtained from organisms exposed to plutonium in a single exposure and in 

 continuous exposure contained a majority of plutonium in compounds of molecular size 

 greater than Pu— DTPA, which was used as the source of soluble plutonium. Furthermore, 

 there appeared to be a difference in plutonium chemical form when plutonium complexes 

 formed on simple interaction of plutonium with metabolites (single exposure) and 

 plutonium complexes formed on interaction after continuous plutonium exposure of the 

 culture were compared. This suggests either that the culture grown in the continuous 

 presence of plutonium contained metabolites capable of interacting with plutonium 

 which were different chemically from those produced by the culture grown in the 

 absence of plutonium or that the culture grown in the presence of plutonium contained 

 different organisms that were capable of adaptive response to the element leading to the 

 synthesis of compounds relatively specific to detoxification of plutonium. 



Further chemical characterization with the use of thin-layer chromatography and 

 electrophoresis verified differences in plutonium form. Several solvents of different 

 polarities and pH values were used to provide a range of chemical conditions for 

 separation. Solvent systems included: A, butanol— pyridine, a system used in the 

 resolution of amino acids; D, pentanol— formic acid, a system used in the separation of 

 sugars and sugar acids; and G, water— acetic acid, a solvent used in the resolution of 

 keto-acids and sugars. These systems were used to resolve plutonium as Pu— DTPA and 

 plutonium in the soluble exocellular and soluble intracellular fractions of the above 

 cultures (Fig. 8). Thin-layer chromatography with the use of solvent A indicated that the 

 exocellular fraction contained one component of chromatographic mobility different 

 from the added Pu-DTPA, but the complex remained present in detectable quantities. 

 The intracellular soluble fraction contained a component of lesser chromatographic 

 mobility, but there was no evidence of Pu-DTPA. Solvents D and G did not provide good 

 resolution. Solvent D did not mobilize Pu-DTPA or other possible complexes; solvent G 

 mobilized Pu-DTPA and indicated the presence of immobile plutonium components in 

 the exocellular and intracellular fractions, but these were not resolved. 



