Bacterial community composition in the water column of the deepest freshwater Lake Baikal as determined by next-generation sequencing

Abstract

The composition of bacterial communities in Lake Baikal in different hydrological periods and at different depths (down to 1515 m) has been analyzed using pyrosequencing of the 16S rRNA gene V3 variable region. Most of the resulting 34 562 reads of the Bacteria domain have clustered into 1693 operational taxonomic units (OTUs) classified with the phyla Proteobacteria, Actinobacteria, Chloroflexi, Bacteroidetes, Firmicutes, Acidobacteria and Cyanobacteria. It has been found that their composition at the family level and relative contributions to bacterial communities distributed over the water column vary depending on hydrological period. The number of OTUs and the parameters of taxonomic richness (ACE, Chao1 indices) and diversity (Shannon and inverse Simpson index) reach the highest values in water layers. The composition of bacterial communities in these layers remains relatively constant, whereas that in surface layers differs between hydrological seasons. The dynamics of physicochemical conditions over the water column and their relative constancy in deep layers are decisive factors in shaping the pattern of bacterial communities in Lake Baikal.

Variation of bacterial communities along the vertical gradient in Lake Issyk Kul, Kyrgyzstan

“…This is the first study that describes the diversity and composition of bacterial communities in Lake Issyk Kul, Kyrgyzstan, using next generation sequencing and a high number of sampling points along the vertical gradient. The main finding is that the depth plays a decisive role in the variations of the community structure, which is consistent with the results of other studies conducted in deep lakes such as Lake Baikal in Russia, Crater Lake in the United States, and Lake Tanganyika in Central Africa (Glöckner et al 2000; Urbach et al 2001; Bel’kova et al 2003; De Wever et al 2005; Kurilkina et al 2016) . However, Lake Issyk Kul showed some differences in terms of the composition of the most abundant groups in the different layers, probably related to particular brackish conditions and high oxygenation.…”

“…Previous studies have shown the presence of Chloroflexi and Planctomycetes in deep waters (Urbach et al 2001; De Wever et al 2005; Breuker et al 2013; Campbell and Kirchman 2013; Luo et al 2014; Kurilkina et al 2016; Li et al 2018), however, this is the first study showing the dominance of these two phyla, and more specifically of Anaerolineaceae and Phycisphaeraceae-Gimesiaceae, in the deeper layers of a lake. The microorganisms in the deep waters of Lake Issyk Kul face aphotic conditions, higher salinity than in the surface, lower temperatures, high hydrostatic pressure, and high availability of oxygen.…”

“…The current knowledge about the distribution of planktonic bacterial communities along the vertical gradient in lake ecosystems is limited, particularly in lakes with depths greater than 200 m. Of the total existing lakes globally, only a few contain mesopelagic ecosystems (200 to 1000 m). Of these, only a handful has been studied concerning diversity and composition of their microbial communities, with examples mainly from Lake Baikal in Russia (Glöckner et al 2000; Bel’kova et al 2003; Kurilkina et al 2016), Lake Tanganyika in Africa (De Wever et al 2005), and Crater Lake in the United States (Urbach et al 2001).…”

Ubiquity and quantitative significance of bacterioplankton lineages inhabiting the oxygenated hypolimnion of deep freshwater lakes

“…Although these assumptions are speculative, future studies should verify them given their ubiquity and quantitative importance in deep freshwater systems. Indeed, the dominance of CL500-11 has been reported in the two largest deep freshwater systems on Earth, the Laurentian Great Lakes (Rozmarynowycz, 2014;Denef et al, 2016) and Lake Baikal (Kurilkina et al, 2016). of the hypolimnion inhabitants.…”

Microorganisms Collected from the Surface of Freshwater Lakes Using a Drone Water Sampling System (DOWSE)

“…Some bacteria are decomposers, breaking down organic matter into nitrate, phosphate, and other essential nutrients [1]. The diversity and abundance of microorganisms in lakes can drastically change the water quality of a freshwater system [2]. Cyanobacteria obtain their energy from photosynthesis and provide an important link in the food chain as they introduce oxygen and energy from the sun's light to freshwater systems [1].…”