Application of thin-layer-electrophoresis (pH 6.6, pyridine-acetate buffer system; cellulose support) indicated the presence (Fig. 11) of a relatively large amount of material of greater negative charge than Pu-DTPA in the exocellular fraction along with Pu-DTPA. The Pu liganda in the intracellular fraction were either neutral in charge in this buffer system or were of a molecular size too large to migrate under the conditions of electrophoresis. Similar alterations of Pu form by a single Pu-resistant fungus exposed continously to Pu during growth have also been reported (Robinson Pus Several phenomena may have been responsible for the observed changes in chemical form of Pu. The organism may have synthesized compounds which either bind Pu-DTPA or bind Pu more tightly than DTPA, thereby successfully competing for Pu in the presence of DTPA. Alternatively, the organism may degrade or modify the DTPA moiety allowing Pu transfer to ligands arising from microbial synthesia and degradation. EXOCELLULAR SOLUBLE et al., 1977). The number of known compounds with the potential to bind Pu more strongly than DTPA appears to be quite limited although hydroxamate derivatives, (Emergy, 1974) catechol derivatives, (Tait, 1975} and tetrapyrrole ring systems (Balker, 1969) may exhibit this property. If modification of the Pu-DTPA occurred prior to ligand transfer, then a myriad of microbiaily- produced compounds, e.g., phenolic acids, peptides, and carboxylic acids CONTROL e INITIAL . TLE, Fig. 11. fetare, om SPOTTING . 20 MIT Thin-layer electrophoretic behavior of plutonium separated by gel permeation chromatography (Senior authors, unpublished). to be elucidated, the solubility (discussed in a previous section) and 160 ® a> potential for complexation may be preliminarily assessed from known chemistry (Table 7), It ia evident that the transuranic elements form DTPA complexes with stabilities similar in magnitude to Pu-DTPA over environmental pH ranges. It may be concluded that complexation with organic ligands produced by soil microflora is highly probable and investigations to identify and characterize the indirect processes and the ligands responsible for complexation of Pu in soil are equally applicable to other transuranic elements. Cycling During Decomposition. A final process whereby the soil microflora may play a role in transformation of the transuranic elementea involves the ® e SOLUBLE were capable, through simple expression of the metabolic potential of Although published information on transuranic elements other than Pu is limited, it is likely that similar transformations will occur. The extent of these transformations will be dependent upon the solubility of the element, its availability to microorganiems, its toxicity to microorganisms and its potential for complexation. While microbial interactions remain 3 INTRACELLULAR have potential for binding Pu (see previous section; also Alexander, 1971). In either case, the Pu was not in the form initially added. Thus, applications of gel permeation chromatography, thin-layer chromatography and thin-layer electrophoresis indicate that cultures of soil microorganiems microorganism present in soil, of changing the chemical form of Pu-DTPA with the resulting formation of a number of Pu complexes exhibiting a range in chemical properties. Differences in Pu distribution in microbial systems and in Pu form resulted from both simple interaction with metabolites and perhaps, more specific processes. These differences were dependent on organism type, metabolism and Pu resistance. DTPA. 162