Comparative molecular biological analysis of the microbial community of the Holocene and Pleistocene deposits of Posol’skaya Shoal, Lake Baikal

The bacterial diversity was studied in sediment layers of Posol’skaya Shoal station (Southern Baikal) belonging to different periods. A set of primers specific to individual bacterial groups was used to analyze the 16S rRNA gene fragments. The bacterial diversity in the Holocene deposits was found to be higher than in the Pleistocene ones. In the upper sediments, a positive PCR reaction with bacterial primers and with specific cyanobacterial and archaebacterial primers was detected. The following phylogenetic groups were revealed in the microbial community of the surface horizon: green nonsulfur bacteria, δ-proteobacteria, β-proteobacteria (Nitrospirae), α-proteobacteria, acidobacteria, crenarchaeota, euryarchaeota, and groups of uncultured bacteria. From the DNA of the Pleistocene deposits, the PCR product was obtained only with bacterial primers. The representatives of the genus Pseudomonas were most closely related to the sequences obtained (95–97% homology).