Bacterial diversity and activity along a salinity gradient in soda lakes of the Kulunda Steppe (Altai, Russia)

Here we describe the diversity and activity of sulfate reducing bacteria along a salinity gradient in four different soda lakes from the Kulunda Steppe (South East Siberia, Russia). For this purpose, a combination of culture-dependent and independent techniques was applied. The general bacterial and SRB diversity were analyzed by denaturing gradient gel electrophoresis (DGGE) targeting the 16S rDNA gene. DNA was used to detect the microbial populations that were present in the soda lake sediments, whereas ribosomal RNA was used as a template to obtain information on those that were active. Individual DGGE bands were sequenced and a phylogenetic analysis was performed. In addition, the overall activity of SRB was obtained by measuring the sulfate reduction rates (SRR) and their abundance was estimated by serial dilution. Our results showed the presence of minor, but highly active microbial populations, mostly represented by members of the Proteobacteria. Remarkably high SRR were measured at hypersaline conditions (200 g L(-1)). A relatively high viable count indicated that sulfate reducing bacteria could be highly active in hypersaline soda lakes. Furthermore, the increase of sodium carbonate/bicarbonate seemed to affect the composition of the microbial community in soda lakes, but not the rate of sulfate reduction.