Diversity and activity of bacteria in uranium waste piles


Diversity and activity of bacteria in uranium waste piles

Selenska-Pobell, S.

The pollution of the environment with toxic metals is one of the most severe problems of our industrial age. Uranium mining waste piles are a subject of particular attention, because in the soils, sediments, and drainage waters of these environments significant amounts of many hazardous metals are present, such as uranium, selenium, molybdenum, arsenic, cadmium, chromium, mercury, lead, copper, nickel and zinc (Francis, 1990). In addition, significant amounts of thorium, radium, polonium and other decay products may also be present in the so-called uranium 'mill tailings' where the extraction of uranium from the ores was performed.

Even in the most heavily polluted uranium wastes, large numbers of bacteria are present (Cerda et al., 1993; Goebel & Stackebrandt, 1994; Shippers et al., 1994). Moreover, different groups of bacteria can interact in different ways with metals and radionuclides (see Chapters ????). Some of the most important mechanisms by which bacteria can biotransform and influence the mobilization and/or immobilisation of metals are listed below:

i) direct oxidation and/or reduction of metals, which affect their solubility (DiSpirito & Tuovinen, 1982; Lovley, 1993; Nelson et al., 1999; Sharma et al. 2000; Wildung et al., 2000);
ii) direct or indirect oxidation of metal sulfides and the associated solubilization of certain elements (Bosecker, 1997; Krebs & Brandl, 1997);
iii) indirect alteration of metal speciation caused by microbially-induced pH and Eh changes in the medium (Bosecker, 1997; Bacelar-Nicolau & Johnson, 1999);
iv) bioaccumulation [biosorption by cell surface polymers (DiSpirito et al., 1983; Douglas & Beveridge, 1998; Macaskie et al., 1992; Panak et al., 1999; Selenska-Pobell et al., 1999; Valentive et al., 1996) and/or uptake of metals inside the cells (Klaus et al., 1999; Marques et al., 1991; Purchase et al., 1997)];
v) bio-mineralization, including induction of metal precipitation by specific metabolic functions and the consequent generation of minerals (Brown and Beveridge, 1998; Douglas and Beveridge, 1998; Francis, 1998);
vi) release of biosorbed metals by chelation, alkylation, or decomposition (Bosecker, 1997; Francis, 1990; Francis et al., 1998).
It is clear that the bacterial activities described above strongly influence the fate and migration of toxic metals in and outside the sites where uranium mining has been performed. In addition to the living cells, significant amounts of different bacterial metabolites are present in the wastes and these also interact with the heavy metals and influence their behaviour. For these reasons, knowledge of the diversity and activity of the indigenous bacteria in the uranium waste piles is of fundamental importance for understanding the biogeochemical processes occurring in these environments and especially for modelling the migration of the heavy metals and radionuclides.

Until recently, information about bacterial diversity in uranium waste piles was limited to several studies dealing with culturable bacteria (Berthelot et al., 1997; Cerda et al., 1993; Francis et al., 1991; Goebel & Stackebrandt, 1994; Shippers et al., 1994). This, however, is not sufficient because only a few percent of natural bacterial populations can be cultured and studied in the laboratory (Chapter 2) due to our limited knowledge of the nutrient requirements and other life-necessities for most bacterial species in nature (Pace, 1997; Service, 1997; Ward et al., 1990). The development and application of molecular approaches in bacterial ecology during the last decade has revealed a tremendous prokaryotic diversity which was overlooked by traditional culture enrichment techniques (Byers et al., 1998; Chandler et al., 1997; Dojka et al., 2000; Pace, 1997; Service, 1997).

One of these approaches, 16S rDNA retrieval, has been applied to analysis of bacterial diversity in deep granitic rocks and in an aquifer around a nuclear fuel repository in Sweden (chap...

  • Book (Authorship)
    Interactions of Bacteria with Radionuclides Elsevier Sciences, Oxford, UK pp. 225-253

Permalink: https://www.hzdr.de/publications/Publ-4596
Publ.-Id: 4596