Bacterial and Archaeal Diversity in Ground Waters of the Siberian Deep--Well Radioactive DisposaI Site Tomsk-7

Microbial diversity was studied in water samples collected from depths of 290 to 324 m near the radioactive waste injection site Tomsk-7 in Siberia, Russia. The biomass from the samples was concentrated via consequent filtration on filters with pore sizes of 1.2, 0.45 and 0.22 µm. 16S rDNA clone libraries were constructed for total DNA recovered simultaneously from the three filters and also for the DNA extracted individually from 0.45 and 0.22 µm filters in parallel. The analysis of the 16S rDNA libraries demonstrated that the estimation of microbial diversity strongly depends on the way of collecting the biomass.
About 65% of the clones retrieved in the total DNA were affiliated to the Rhodocyclus group. The rest of the clones represented very diverse bacterial groups. Euryarchaeota and Grenarchaeota were also identified in this total DNA.
No archaeal sequences were amplified in the 0.45 and 0.22 µm filter DNA. This indicates that the archaea were associated (possibly with some bacteria) with the larger aquatic particles.
In the 0.45 mm library the representatives of the Rhodocyclus group represented 30% of the total number of clones. Another 20% of the clones were affiliated with a low identity to a novel cyanobacteria related lineage.
Sequences representing the same "cyanobacteria-like" lineage were also found in the 0.22 µm library. However, populations of possibly oligotrophic Cytophagales were the most predominant in the latter library and represented about 55% of the clones. Microdiverse ultramicrobacterial isolates were cultured from one 0.22 µm filter and characterized morphologically and physiologically.