on the vertical distribution of microorganisms in lake baikal during spring deep-water renewal

The vertical distribution of microorganisms during spring deep-water renewal in Lake Baikal was studied. The downward advection of trophogenic waters was found to create conditions for the extensive growth of microorganisms capable of decomposing and mineralizing organic carbon, nitrogen, and phosphorus in deep water layers. These processes occur annually at spring thermal bars near the underwater slope of Lake Baikal, whereas in its pelagic zone, the deep intrusions of waters rich in organic material are observed only in the years when enhanced deep-water renewal is accompanied by a high spring yield of phytoplankton.     

Taxonomic composition of Lake Baikal bacterioneuston communities

The taxonomic composition of microbial communities of Lake Baikal surface microlayer was studied by pyrosequencing of the 16S rDNA amplicons. Statistically reliable differences were found between bacterioneuston of the shallow and deep-water stations. The shallow station community was characterized by higher diversity than the deep-water one. While bacterioneuston communities were shown to be less diverse than the water column communities, their diversity was comparable to that of other biofilm associations. Microbial communities of Lake Baikal surface microlayer were shown to be similar to those of the water column in the composition of predominant phyla, while differing considerably at the genus level. Bacterioneuston of Lake Baikal was comparable to microbial communities of the surface microlayer of other freshwater basins, although it was characterized by high abundance of the Alphaproteobacteria and Verrucomicrobia. High abundance of photoheterotrophs compared to the water column communities of other freshwater basins was another distinctive feature of Lake Baikal bacterioneuston. Our results showed the Lake Baikal surface microlayer to be a specific microbial community with low species diversity and relatively high abundance of photoheterotrophic microorganisms.     

Transformation of Organic Matter by a Microbial Community in Sediments of Lake Baikal under Experimental Thermobaric Conditions of Protocatagenesis

Early diagenesis of organic matter in bottom sediments of Lake Baikal is a focus of many geochemical studies, because it is one of the few sites of petroleum formation in a nonmarine environment. Although Baikal is a rift lake and considered one of the prospective fields for deep biosphere investigations, the transformation processes of organic matter by microbial communities from deep bottom sediments and likely entering of the microorganisms from deep sediments into the near-surface sediments were not previously studied in Lake Baikal. The natural microbial community from near-surface sediments of the cold methane seep Goloustnoe (Southern Baikal Basin) was incubated with methane and the diatom Synedra acus at 80°C and 49.5 atm to simulate catagenesis. The 11-month incubation yielded the enrichment culture of viable thermophilic microorganisms. Their presence in low-temperature sediment layers may be indicative of their migration through fault zones together with gas-bearing fluids. After culturing, molecular biological methods allowed for the detection of both widespread microorganisms and unique clones whose phylogenetic status is currently unknown. The sediment after the experiment showed the formation of polycyclic aromatic hydrocarbon, retene. Retene can be either a conifer or algal biomarker, thus, interpretation of paleoclimate data is tenuous.     

The classification and the monitoring of the state of mouth riverine and lacustrine ecosystems in lake Baikal based on the composition of local microbiocenoses and their activity

The paper presents the results of the long-term investigation of microbial communities in the technogenically vulnerable mouth riverine and lacustrine ecosystems of Lake Baikal. The structural and functional parameters of the microbial communities were analyzed from the standpoint of developing destructive processes. The analysis showed that the total number of microorganisms (TNM), the number of saprophytic bacteria (NSB), and bacterial production (BP) were greater in the river-mouth water than in the near-mouth lake water. In the offshore direction, TNM and NSB decreased by a factor of 1.5 to 2, and BP decreased by a factor of 4 to 7. Based on TNM, NSB, and BP data, we classified the Lake Baikal rivers with respect to the degree of the impact of human activities on them. The degrading capability of the riverine microbial communities was found to be such that they degrade daily from tenths of a percent to 3.5% of the total amount of organic compounds polluted the river waters.     

Plankton composition and water chemistry in the mixing zone of the Selenga River with Lake Baikal

Chemical and biological components of the Selenga River waters, the largest tributary of Lake Baikal, differ significantly from the lake waters. Active transformation processes of river waters into the lake ones occur in the vast barrier-like zone in the river-sea boundary areas. This study presents results on the spatial distribution and dynamics of water chemistry as well as the quantity and diversity of phyto- and bacterioplankton at a distance of 14 km off the Selenga River mouth. The most representative tracers of river and lake waters are total amount of ions and sulphates. Principal changes of chemical and biological parameters were fixed at 1–3 km off the Selenga River mouth that was determined as a mixing zone. Intense development of phytoplankton and eukaryotic picoplankton causing the decrease of nitrate and phosphate concentrations and organic matter rise were registered in this area. Gradual replacement of river phytoplankton by the lake one, abundance reduction of microorganisms and organotrophic bacteria and percentage increase of oligotrophic and psychrotolerant bacteria occurred in the mixing zone. Replacement of PC-rich picocyanobacteria by PE-rich ones was also recorded here. At a distance of 5–7 km off the shore, nutrient concentration and plankton composition were similar to those of Lake Baikal.     

Investigation of distribution,species composition,and degree of resistance to antibiotics of the bacteria of the <Emphasis Type="Italic">Enterococcus</Emphasis> genus in Lake Baikal

The paper presents the result of investigation of species composition, distribution and degree of resistance to antibiotics of the Enterococcus bacteria in Lake Baikal. It is shown that they live in littoral zones of the lake. In the deep-water part of the lake the studied microorganisms are not found. We isolated 120 strains identified as E. faecium, E. avium, E. faecalis, E. mundii, E. hirae, E. durans, E. gallinarum. On the whole, the strains of enterococcus isolated from Lake Baikal are characterized as antibiotic-sensitive. Nevertheless, the antibiotic-resistant strains of enterococci are found in the studied collection, including those with typical intermediate level of resistance to vancomycin.     

The Classification and the Monitoring of the State of Mouth Riverine and Lacustrine Ecosystems in Lake Baikal Based on the Composition of Local Microbiocenoses and Their Activity

The paper presents the results of the long-term investigation of microbial communities in the technogenically vulnerable mouth riverine and lacustrine ecosystems of Lake Baikal. The structural and functional parameters of the microbial communities were analyzed from the standpoint of developing destructive processes. The analysis showed that the total number of microorganisms (TNM), the number of saprophytic bacteria (NSB), and bacterial production (BP) were greater in the river-mouth water than in the near-mouth lake water. In the offshore direction, TNM and NSB decreased by a factor of 1.5 to 2, and BP decreased by a factor of 4 to 7. Based on TNM, NSB, and BP data, we classified the Lake Baikal rivers with respect to the degree of the impact of human activities on them. The degrading capability of the riverine microbial communities was found to be such that they degrade daily from tenths of a percent to 3.5% of the total amount of organic compounds polluting the river waters.     

Diversity of laboratory-reared prokaryotes in the bottom sediments of the Akademichesky Ridge,Lake Baikal

Microbial communities in the bottom sediments of the Akademichesky Ridge, Lake Baikal, were studied. The samples were taken by deep drilling BDP-96 (a 100-m core). Vertical distribution of the prokaryotes with different physiological characteristics was studied for the core. The phylogenetic analysis of the organotrophic laboratory-reared microorganisms revealed the clusterization of Baikal strains and species which have not been identified yet.     

Phylogenetic diversity of microorganisms associated with the deep-water sponge Baikalospongia intermedia

The diversity of bacteria associated with deep-water sponge Baikalospongia intermedia was evaluated by sequence analysis of 16S rRNA genes from two sponge samples collected in Lake Baikal from depths of 550 and 1204 m. A total of 64 operational taxonomic units, belonging to nine bacterial phyla, Proteobacteria (classes Alphaproteobacteria, Betaproteobacteria, Gammaproteobacteria, and Deltaproteobacteria), Actinobacteria, Planctomycetes, Cloroflexi, Verrucomicrobia, Acidobacteria, Chlorobi, and Nitrospirae, including candidate phylum WS5, were identified. Phylogenetic analysis showed that the examined communities contained phylotypes exhibiting homology to uncultured bacteria from different lake ecosystems, freshwater sediments, soil and geological formations. Moreover, a number of phylotypes were relative to psychrophilic, methane-oxidizing, sulfate-reducing bacteria, and to microorganisms resistant to the influence of heavy metals. It is noted that the unusual habitation conditions of deep-water sponges contribute to the taxonomic diversity of associated bacteria and have an influence on the presence of functionally important microorganisms in bacterial communities.     

Distribution of dissolved organic carbon in Lake Baikal and its watershed

 Concentrations of dissolved organic carbon (DOC) in Lake Baikal ranged from 90 to 110 μM C, considerably higher than those in oceanic environments. The DOC concentrations in the epilimnion were higher than those in the hypolimnion. Since particulate organic carbon (POC) concentrations in the pelagic waters of Lake Baikal were <10–40 μM C in the epilimnion and 2–5 μM C in the hypolimnion, DOC constitutes a major component of the organic carbon pool in Lake Baikal, especially in the deep layers. The DOC concentrations downstream of the Barguzin and Selenga Rivers were quite high (400–500 μM C). Probably because of the high concentrations of DOC in these rivers, the DOC levels in Barguzin Bay and offshore at the mouth of the Selenga River were higher than those in the pelagic regions of the central and south basins of Lake Baikal. The relationship between DOC and electric conductivity revealed the transport of DOC from rivers to the pelagic area in Lake Baikal. The spatial distribution of DOC suggested that a major part of DOC in the lake was allochthonous (land-derived). Received: July 26, 2002 / Accepted: September 16, 2002 Present address:Research Institute for Humanity and Nature, 335 Takashima-cho, Marutamachi Kawaramachi, Kamigyo-ku, Kyoto 602-0878, Japan Tel. +81-75-229-6167; Fax +81-75-229-6150 e-mail: yos@chikyu.ac.jp Acknowldgments The authors wish to thank Director Prof. M. Grachev and Dr. O. Timoshkin of the Limnological Institute, Siberian Branch, Academy of Science, Russia, for arranging the cruise on Lake Baikal. We are also indebted to Drs. V. Sinyukovich, I. Khanaev, and A. Zhdanov for their kind assistance during the expeditions. We wish to thank Ms. Y. Ito for measuring the DOC concentrations. This work was supported and financed by Grants-in-Aid for Scientific Research from the Ministry of Education, Culture, Sports, Science and Technology (MEXT), Japan (No. 09041159) and for Scientific Research of Priority Area B (No. 11213101) and by the International Geosphere-Biosphere Programme (IGBP) at Nagoya University. Correspondence to:T. Yoshioka     

Microorganisms of Lake Baikal and Lake Nyasa as indicators of anthropogenic influence: prospects of use in biotechnology

Restriction endonucleases (RENs) were detected in 650 microbial strains isolated from water columns and bottom sediments of deep rift lakes, Baikal (Russia) and Nyasa (Southeastern Africa). They enzymes included unique (Fan I, Aca I, and Sse 91) and very rare (Bsi I, and Cci N I) species not typical of aquatic ecosystems. Water columns, deep cores, and bottom sediments of pure areas of the lakes contained no microorganisms with new RENs. Thus, inshore areas of Lake Baikal exposed to anthropogenic influence may contain mutant bacterial strains expressing RENs that have not been described previously.     

Microorganisms of Lake Baikal and Lake Nyasa as Indicators of Anthropogenic Influence: Prospects for Use in Biotechnology

Restriction endonucleases (RENs) were detected in 650 microbial strains isolated from water columns and bottom sediments of deep rift lakes, Baikal (Russia) and Nyasa (Southeastern Africa). They enzymes included unique (Fan I, Aca I, and Sse 91) and very rare (Bsi I, and Cci N I) species not typical of aquatic ecosystems. Water columns, deep cores, and bottom sediments of pure areas of the lakes contained no microorganisms with new RENs. Thus, the inshore areas of Lake Baikal, having been exposed to anthropogenic influences, may contain mutant bacterial strains expressing RENs that have not been described previously.     

Antagonistic activity of actinomycetes of Lake Baikal

It was demonstrated that actinomycetes of Lake Baikal are strong antagonists of other microorganisms. Representatives of the genera Streptomyces and Micromonospora inhibit the growth of bacteria isolated from the lake, as well as of antibiotic-resistant microorganisms causing various human diseases. Baikal actinomycetes display a wide range of antagonistic activity and are potential producers of new biologically active substances.     

Genomic and phenotypic analyses of microorganisms isolated from the sediments of Lake Baikal

Genetic and biochemical methods and morphological examination were used to study microorganisms isolated from samples of deep drilling of the Lake Baikal bottom sediments. Based on blot hybridization patterns, the strains investigated were divided into several groups according to the degree of homology of their genomic DNA. Morphological, biochemical, and ultrastructural characteristics of bacterial strains are described, and their compliance with the genomic analysis data is demonstrated.     

Genomic and Phenotypic Analyses of Microorganisms Isolated from the Sediments of Lake Baikal

Genetic and biochemical methods and morphological examination were used to study microorganisms isolated from samples of deep drilling of the Lake Baikal bottom sediments. Based on blot hybridization patterns, the strains investigated were divided into several groups according to the degree of homology of their genomic DNA. Morphological, biochemical, and ultrastructural characteristics of bacterial strains are described, and their compliance with the genomic analysis data is demonstrated.     

Comparative character of the deep-water and inshore cottoid fishes endemic to Lake Baikal

Lake Baikal's 29 endemic species of cottoid fishes form three groups: shallow-water species in depths to 350 m; eurybathic species from 50 to 1300 m; and abyssal species from 400 to 1600 m. These groups differ in their abilities to withstand high hydrostatic pressure. As in marine deep-water fishes, abyssal cottoids in Baikal have few or no cones in the retina, and some have tubular eyes. Their seismosensory systems predominate, based chiefly on free neuromasts. The proportion of species with canal systems decreases with depth. Diversity of the predominantly gammarid foods also decreases from 45 species in shallow water to five species in deep water, and the lateral line system plays the dominant role in food detection at all depths. Two abyssal cottoids have become secondary pelagic, achieving close to neutral buoyancy through high lipid levels and reduced skeletal mineralization. These forms take advantage of the abundant pelagic planktonic amphipod populations. The adaptations of abyssal forms parallel those seen in deep-water marine fishes.     

Oxygen concentration profiles in sediments of two ancient lakes: Lake Baikal (Siberia,Russia) and Lake Malawi (East Africa)

Oxygen concentration profiles have been measured, by means of with microelectrodes in sediments of Lake Baikal and Lake Malawi, along transects allowing to give a survey of two major ancient Rift lakes: Lake Baikal (Eastern Siberia) and Lake Malawi (East Africa), along depth transects in the constitutive basins of the lakes and/or of relevant depths with regard to oxygen (including including the deepest point, 1680 m, in Lake Baikal). Sediment oxygen penetration depths (SOPs) display very different patterns, depending on the lake in the two lakes. In Lake Baikal, SOPs are variable, show no significant relationship with bathymetric depth and are surprisingly deep on Akademichesky ridge (> 50.0 mm), emphasizing the distinctive feature of this region in the lake. While the Selenga river is an important source of eutrophication, the similarity of SOP-values in the Selenga shallow with those of most other sites suggests either a dilution of organic material by allochthonous matter, or a strong south-to-north transport of particles. In Lake Malawi, available oxygen is restricted to a maximum of three millimetres of the sediment, and there is a negative relationship with bathymetric depth, as a result of a steady decline of oxygen concentration with depth through the water column. Amongst the few parameters known to affect SOPs, the oxygen consumption by the sediment seems the most significant in both lakes. SOP-values furthermore confirm differences in the trophic status of Baikal and Malawi, respectively. The importance of oxygen as a factor likely to create ecological segregation for benthic organisms is discussed. Lake Malawi offers possibilities of bathymetric segregation but no vertical segregation in the sediment. In contrast, no bathymetric segregation related to oxygen is possible in Lake Baikal, but vertical segregation in the sediment is very likely. This revised version was published online in July 2006 with corrections to the Cover Date.     

Thermophilic Bacteria in Lake Baikal Bottom Sediments Associated with Hydrocarbon Discharge

Microbiology - The research was aimed at detection of thermophilic microorganisms in Lake Baikal low-temperature sediments associated with discharge of gas-saturated fluids. Members of the order...     

Antagonistic activity of actinomycetes of Lake Baikal

It was demonstrated that the actinomycetes of Lake Baikal are strong antagonists of other microorganisms. Representatives of the genera Streptomyces and Micromonospora inhibit the growth of bacteria isolated from the lake, as well as of antibiotic-resistant microorganisms causing various human diseases. Baikal actinomycetes display a wide range of antagonistic activity and are potential producers of new biologically active substances.     

Response of microbial communities of Lake Baikal to extreme temperatures

The survival rate, metabolic activity, and ability for growth of microbial communities of Lake Baikal after exposure to extremely low temperatures (freeze-thawing) for different lengths of time have been first studied. It has been shown that short-term freezing (1-3 days) inhibits the growth and activity of microbial communities. The quantity of microorganisms increased after 7- and 15-day freezing. In the periods of maximums, the total number of microorganisms in the test samples was twice as high as in the control. It was established that after more prolonged freezing the microorganisms required more time after thawing to adapt to new conditions. In the variants with 7- and 15-day freezing, the activities of defrosted microbial communities were three or more times higher than in the control. The survival rate and activity of Baikal microorganisms after freeze-thawing confirms the fact that the Baikal microbial communities are highly resistant to this type of stress impact.