After growth for 96 hr, the culturee were separated into cellular and exocellular fractiona, The cell fraction was, in turn, homogenized into intracellular soluble and cell debris fractions. The results of studies in which Pu was added at the stationary growth phase of cultures of fungi or bacteria grown on mixed organic acide or sugare are summarized in Table 5. These cultures, selected only on the basis of their ability to grow on either of two C sources, differed to a first approximation, in their interactions with Pu. In general, the majority of Pu was associated with the exocellular fraction, but significant quantities were insoluble and associated with the cell wall and membrane fractions. However, the distribution of Pu between fractiona was dependent upon microorganism type and C-source. In the case of fungi, the exocellular fraction of organisms grown on the organic acid C source contained less Pu than when mixed sugate were utilized as a C source. The reverse of this relationship occurred with the bacteria. Differences in Pu distribution as a function of C source used in enrichment were also found in cultures grown in the presence of Pu throughout incubation (Table 6). The fungal cultures grown on mixed organic acids Mu no gw au Ba qi7 x mm mit oc one ms * mm aml on =) eod rict “ w wad on eno “ax ~~ mmT Aaond mNA Amn mt red ‘Al > ord ray & a F n OW “doh AB mn on™ oa ca Bui O moG ~ ro . TAM ow a e+ AAW orm An mom FF uw mri < . Maw a4 qa w ™ 3S cow ea aw am m mam om . mowe “ . & mmm Fal as “4 oe > UO tw PED gan HO ug & Av Yo. Age oer ogz Coo g u ‘A BE ou <4 O O & mmm 9000 900900 009 ade wx x Mow Orme me etn woo a Mx Nowe som raw amo AMD HMmw wt mn dad “MMO + ama” naan xx x RAR aay Km mm wm mam are wn wn nN w ” od x oO cal a ooo at add a el 9000 Artest uv wv a H y a) =z exhibited larger concentrations of Pu both in the exocellular fraction and 154 rm 155 v a Hd uv “A u *arithmetic mean of 3 samples. In preliminary (unpublished) studies by the senior authore and others, mixed cultures of soil organisms, fsolated from soil on the basis of C requirements and Pu resistance, were analyzed as to their ability to transport Pu into celle and to alter Pu form in the cellular and exocellular media. In addition an experiment was conducted to distinguish complexation reactions resulting from Pu interactions with metabolites arising from normal metabolic processes and Pu interactions with metabolites arising from Pu resistance. To make thia distinction sojl microorganisms were isolated from soil in the absence of Pu and Pu added at the stationary growth phase of an enriched culture, and, transport and complexation were compared to microbial cultures isolated from Pu-contsining soiland grown in the presence of Pu. om 1 ol ono Q Plutonium Transport to the Spores of Aspergillue niger (Beckert and Au, 1976). There is a growing literature on organic acida and bases, capable of complexing heavy elements, which are produced directly or by secondary syntheses by a variety of microorganisms. These products may be expected to be present in soils (discussed in detail in a previous section). Their concentration and form will be dependent upon the environmental factors influencing microbial metaboliam, such as C-source, (previous section), and their residence time will be dependent upon subsequent chemical and microbiological stability. m mi od Me Table 4. uptake was related to pH ard expected solubility of the Pu added with Pu in the initially soluble nitrate and citrate forme exhibiting a factor of 2 to 3 greater uptake than the dioxide (Table 4). Availability to microorganisms of the Pu in citrate and nitrate might be expected to be considerably higher than the oxide from solubility considerations at the pCi/ml level. The relatively high microbial availability of Pu ae the oxide is highly significant, and further studies are warranted to determine the mechanisms of solubilization and uptake and the significance of microorganisms in recycling processes,