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Down into the Earth: microbial diversity of the deepest cave of the world

Abstract In our work, microbial diversity of Krubera-Voronja cave was evaluated in the view of the frequency of human visits in different locations as well as the sampling depth. Sampling in this cave was performed at depths of 220 m to 1640 m. Cultivation-independent method, namely barcoded pyrosequencing of 16S rRNA gene, was used for this analysis. Our results demonstrated high bacterial diversity at the phylum and genus levels. We have shown that the bacterial diversity at the phylum level depends on both the sampling depth and the frequency of human visits in Krubera-Voronja cave. Frequently visited locations were more diverse at the phylum level than the rarely visited branches. The total number of bacterial genera both per phylum and per sample correlated with the frequency of human visits but not with the sampling depth. Some genera, found in Krubera-Voronja cave, seem to be absent or very rare in other caves. The present study represents the first report on the microbial diversity in Krubera-Voronja cave