Changes in archaeal community of a uranium mining waste pile induced by treatments with uranyl or sodium nitrate.

Changes in the archaeal community of a uranium mining waste pile, called Haberland caused by the addition of uranyl or sodium nitrate were investigated by using the 16S rRNA gene retrieval. The natural archaeal diversity in studied environment was limited to only a few lineages of mesophilic Crenarchaeota, predominantly of subgroup 1.1a. Addition of and subsequent incubation with uranyl nitrate for 4 weeks resulted in a significant shifting of the archaeal populations to the soil/sediment cluster 1.1b of Crenarchaeota. The proliferation of the latter populations occurred independently of the amount of the added uranium and the aeration conditions during the incubation. The same shifting of the archaeal populations was also observed in the parallel control samples which were supplemented with sodium nitrate.
Efforts to culture members of the 1.1b Crenarchaeota resulted in their enrichment together with representatives of Firmicutes, mainly of Clostridium spp. Clostridia can effectively interact with uranium and they can also fermentatively reduce nitrate to ammonium. Because an ammonia oxidizing activity was deduced on the basis of meta-genomic analyses of the closest relative to the stimulated in our case 1.1b populations, we speculate that the clostridia possibly supply the crenarchaeal members of the recovered synergetic consortium with ammonia.