Bacterial diversity in water samples from two uranium mill tailings as revealed by 16S rDNA retrieval

Bacterial diversity was assessed in water samples collected from two uranium mill tailings, one in Germany and one in the USA, by using the 16S rDNA retrieval. Mainly individual RFLP types were found in the 16S rDNA library constructed for the samples of the German tailings, Gittersee/Coschütz, that indicated a high bacterial diversity. Several small groups of Proteobacteria and of Cytophagales were identified in those samples as well. Significantly lower bacterial diversity was demonstrated in the samples collected from the Shiprock tailings in the USA, which were predominated by a few large populations of gamma-Proteobacteria.
Key words: bacterial diversity, 16S rDNA, uranium mill tailings
Introduction: Bacteria significantly influence the migration and the toxicity of heavy metals and radionuclides in nature due to their ability to biotransform and accumulate them [1,2]. Uranium mining wastes are contaminated with radionuclides and other toxic metals [2]. The toxicity of uranium is primarily attributed to its chemical properties rather than to its radioactivity [3]. As in other extreme environments, most parts of the indigenous bacterial populations in the uranium mining wastes are not yet cultured due to the limited knowledge of their life necessities. The problems of culturability in the analysis of bacterial diversity were overcome during the last decade by the application of direct molecular methods for analysis, such as the 16S rDNA retrieval [4]. This molecular method was successfully used for compositional analysis of the natural microbial communities in many different environments [5,6,7]. The aim of the present work was to assess bacterial diversity in water samples collected from two uranium wastes by using the 16S rDNA retrieval.
Materials and methods. Samples collection. Samples were collected from two uranium mill tailings: Gittersee/Coschütz, a former uranium-coal mine, near the town of Dresden in Germany and Shiprock, New Mexico, in the USA, located in north western New Mexico,