Bacterial and archaeal diversity in waters at the Siberian deep-well monitoring site Tomsk-7

Microbial diversity was studied in water samples collected at depths of 290 to 324 m from the monitoring site S15 near the city of Tomsk, Siberia, Russia. The 16S rDNA retrieval was applied, in order to overcome the problems of culturability of the bacteria and archaea indigenous for that extreme habitat. The biomass from the samples was concentrated via consequent filtration on a glass-fibre filter and on filters with pore sizes of 0.45 and 0.22 µm. In this work two bacterial clone libraries were analysed: one constructed for the DNA isolated from the biomass collected on the filter with a size of 0.45µm and another one for those of the 0.22µm filter. In addition, an archaeal clone library was generated for the total DNA extracted simultaneously from all the tree filters (unfractioned DNA). Comparative analyses of the two bacterial libraries revealed significant differences in the predominant groups and in the species composition. In the 0.45µm clone library a dominance of Dechlorosoma spp. populations was found. This result is in agreement with our previous study on bacterial diversity in water at the site S15 which was performed by using total unfractioned DNA (1). However, in contrast of that previous analysis, now the predominance of the Dechlorosoma spp. was not too strong and we were able to find a larger variety of species from: d-subclass of Proteobacteria, Gramm positive bacteria, and in addition members of Candidate divisions OP8, TM7 and the Termite group. In the 0.22µm clone library Dechlorosoma sp. was not identified any more. In this case populations of Chrysobacterium spp. from the Cytophaga/Flavobacterium/Bacteroides group were predominant. There were some common Proteobacterial and Actinobacterial species, which were identified in both the 0.45µm and the 0.22µm libraries. Interestingly, relatively dense and diverse populations of deeply branched not yet cultured Cyanobacteria were found in both bacterial clone libraries. The phylogenetic analysis of Archaeal populations in the S15 sample revealed the presence of sequences which belong to Crenarchaeota and Euryarchaeota. The members of the latter were methanogens and some of them were related to clones identified in metal-rich freshwaters by others (2). Most of the Crenarchaeota 16S rDNA sequences were also similar to those found in other metal-rich environments (3).
Our analysis indicates that microbial communities at the monitoring site S15 are rather complex and diverse. The 0.45µm clone library exhibits greater overall diversity than the 0.22µm clone library. The archaeal populations are represented mainly by clones affiliated with organisms found in other metal pollutd environments.

References:

1. Nedelkova, M., et al. (2003) Environmental Geology (in press).
2. Stein, L. et al. (2001) Env. Microb. 3(1) : 10-18.
3. Stein, L. et al. (2002) FEMS Microb. Ecol. 42 : 431-440.