Comparative Microbial Diversity in Uraniuim Wastes in Germany and in the USA

Structures of the natural bacterial and archaeal communities in soil and water samples from three U wastes in Germany and from two in the USA were compared by using the 16S rDNA and the RISA retrievals. We found that the composition of the bacterial communities is very diverse and site-specific. However, several particular groups of bacteria including also novel lineages were identified in the samples of all habitats. Some of the retrieved 16S rDNAs were related to sequences already found in other heavy metal contaminated environments and it seems that they represent not yet cultured bacterial populations characteristic for the latter.
A quantitative analysis of the Geobacter sp. populations demonstrated that they are present in low but site-specific number at the studied environments.
The archaeal populations in the studied environments were, in contrast to the bacterial, not very dense and they were limited to only two lineages of not yet cultured groups of Crenarchaeotae. Only in one of the samples studied representatives of methanogenic Euryarchaeotae were identified.
Chemolithoautotrophic strains involved in U mobilization and also heterotrophic U reducing and immobilizing strains were cultured from the samples from the U wastes. In addition, several ultramicrobacterial isolates were cultured on oligotrophic media. These isolates were characterized morphologically and physiologically. Their interactions with U and several other metals were studied by using ICP-MS, EXAFS, and IR spectroscopy.