Irina V. Tikhonova

Ecological development and genetic diversity of Microcystis aeruginosa from artificial reservoir in Russia.

Microcystis aeruginosa is a well-known Cyanobacterium responsible for the formation of toxic water blooms around the world. Shallow, warm, and eutrophic reservoirs provide the most favourable conditions for M. aeruginosa development. Numerous studies have been devoted to this species, but there still is a necessity to develop additional approaches for the monitoring of cyanobacteria in reservoirs. In this study, M. aeruginosa in the water column of a hypereutrophic Siberian reservoir was investigated by fluorescence, light, and electron microscopy as well as genetic analysis using a mcyE marker. Here, we demonstrate the genetic diversity and features of the fluorescence spectra for different ecotypes of this species. We suggest that a fluorescence approach can be used to identify M. aeruginosa in a natural environment in order to increase the effectiveness of ecological monitoring and water quality evaluation.

Age-related changes of skin blood flow during postocclusive reactive hyperemia in human

The objective was to study age‐related alterations in the time‐amplitude characteristics of the oscillatory components of peripheral blood flow in healthy humans during postocclusive reactive hyperemia.

Identification of Cyanobacterial Producers of Shellfish Paralytic Toxins in Lake Baikal and Reservoirs of the Angara River

The goal of the present work was to search for PST� producing cyanobacteria in Lake Baikal and reservoirs of the Angara River using a marker for the polyketide synthase gene stxA and to detect saxitoxin and its ana� logues by enzymelinked immunosorbent assay (ELISA) and mass spectrometry. Samples from Lake Baikal were collected in August 2010 in the coastal zone of the Barguzin and Kurkut Bays (Maloe More Strait). Samples were taken from the Irkutsk reservoir (near Patrony village), Bratsk res� ervoir (near NovoDolonovo village), and UstIlimsk reservoir (near Zheleznodorozhnik settlement) in July 2010. Plankton was sampled with a Ruttner sampler from 1�m depth and with an Apstein plankton net by filtration of the upper 1.5�m water layer. The bottle samples were used for qualitative and quantitative assessment of cyanobacteria as described previously (5). Total DNA was extracted from net samples fixed with 70% ethanol using the DNAsorb kit (InterLab� Servis, Russia). The

Stratified distribution of nutrients and extremophile biota within freshwater ice covering the surface of Lake Baikal

Biological entities and gradients of selected chemicals within the seemingly barren ice layers covering Lake Baikal were investigated. Ice cores 40–68 cm long were obtained from inshore and offshore sites of Southern Lake Baikal during the cold period of a year (March–April) in 2007 and 2008. In microscopic observations of the melted ice, both algae and bacteria were found in considerable numbers (>103 cells/L and >104 cells/ml, respectively). Among all organisms found, diatom was generally the most predominant taxon in the ice. Interestingly, both planktonic and benthic algae were present in considerable numbers (2–4×104 cells/L). Dominant phototrophic picoplankton were comprised of small green algae of various taxa and cyanobacteria of Synechococcus and Cyanobium. The bacterial community consisted mostly of short rod and cocci cells, either free-living or aggregated. Large numbers of yeast-like cells and actinomycete mycelium were also observed. Concentrations of silica, phosphorus, and nitrate were low by an order of magnitude where biota was abundant. The profile of the ice could be interpreted as vertical stratification of nutrients and biomass due to biological activities. Therefore, the organisms in the ice were regarded to maintain high activity while thriving under freezing conditions. Based on the results, it was concluded that the freshwater ice covering the surface of Lake Baikal is considerably populated by extremophilic microorganisms that actively metabolize and form a detritus food chain in the unique large freshwater ecosystem of Lake Baikal.

Age-related differences in the dynamics of the skin blood flow oscillations during postocclusive reactive hyperemia

Age-related changes in peripheral microcirculation were studied using laser Doppler flowmetry in 60 apparently healthy subjects. The response of microcirculation to short-term ischemia was studied using the occlusion test. Changes in the amplitude of the peripheral blood flow oscillations were determined using time-amplitude analysis based on continuous adaptive wavelet filtration. The oscillation amplitude in the frequency range of the heart rate was found to reach the maximum with a delay after the removal of the occlusion, whereas in the range of the respiratory rhythm, no delay was observed. The hyperemic response to short-term ischemia is assumed to develop under the predominant influence of the arterial-arteriolar component, whereas the dynamics of amplitude oscillations in the range of the respiratory rhythm is a result of the devastation of the venular component after removal of occlusion. In response to short-term ischemia, the maximum oscillation amplitudes of myogenic, neurogenic, and endothelial rhythms decreased with age, which demonstrates the restriction of the regulatory control of the peripheral blood flow by the corresponding systems.

First detection of benthic cyanobacteria in Lake Baikal producing paralytic shellfish toxins

Cyanobacteria were screened from the surface of diseased sponges, stone and bedrock in Lake Baikal for the presence of saxitoxin using enzyme-linked immunosorbent assay. In sequel, eight paralytic shellfish toxin (PST) variants were identified using a MALDI mass spectrometry. Microscopic examination found that Tolypothrix distorta dominated in the biofouling samples. PCR and sequencing detected sxtA gene involved in saxitoxin biosynthesis, thereby providing evidence of the PST producing potential of Baikal cyanobacterial communities inhabiting different substrates.

Diversity of cyanobacterial species and phylotypes in biofilms from the littoral zone of Lake Baikal.

The majority of naturally occurring biofilms contain numerous microorganisms that have not yet been cultured. Additionally, there is little information available regarding the genetic structure and species diversity of these communities. Therefore, we characterised the species diversity, structure and metagenome of biofilms grown on stones and steel plates in the littoral zone of Lake Baikal (East Siberia, Russia) by applying three different approaches. First, light microscopy enabled identification of the species diversity of biofilm-forming cyanobacteria on different substrates with the dominance of Rivularia rufescens, Tolypothrix limbata, Chamaesiphon fuscus, Ch. subglobosus, and Heteroleibleinia pusilla. Additionally, scanning electron microscopy was used to show the spatial structure of biofilms. Finally, sequence analysis of 30,660 16S rRNA clones indicated a high diversity within the biofilm communities, with the majority of the microbes being closely related to Cyanobacteria (8–46% sequences), Proteobacteria (14–43%), and Bacteroidetes (10–41%). Rivularia sp., Pseudanabaena sp., and Chamaesiphon spp. were the dominant cyanobacterial phylotypes.

Identification of two cyanobacterial strains isolated from the Kotel’nikovskii hot spring of the Baikal rift

Two cyanobacterial strains, Pseudanabaena sp. 0411 and Synechococcus sp. 0431, were isolated from a sample collected in the Kotel’nikovskii hot spring of the Baikal rift. According to the results of light and transmission electron microscopy, as well as of the phylogenetic analysis of the 16S rRNA gene, these cyanobacteria were classified as Pseudanabaena sp. nov. and Synechococcus bigranulatus Skuja. The constructed phylogenetic tree shows that the studied strains are positioned in the clades of cyanobacteria isolated from hydrothermal vents of Asia and New Zealand, separately from marine and freshwater members of these genera, including those isolated from Lake Baikal.

Saxitoxin-Producing cyanobacteria in Lake Baikal

Cyanobacteria containing neurotoxic saxitoxin synthesis genes were found in the coastal zone of Lake Baikal near the village of Turka for the first time. Phylogenetic analysis showed that the sequences of saxitoxin synthesis genes belong to the genus Anabaena Bory. Saxitoxin concentration in the water according to ELISA was 1.93 ± 0.64 mg/L. The genetic and taxonomic composition of the bacterial community of the central part of Lake Baikal was characterized using 16S rRNA gene pyrosequencing. It was established that the phylum Cyanobacteria dominated in the composition of summer bacterioplankton in both littoral and pelagic zones of the lake, but higher species diversity was found in the plankton of littoral zone.

Nitrogen-fixing cyanobacterium Trichormus variabilis of the Lake Baikal phytoplankton

A new filamentous cyanobacterial strain BAC 9610 was isolated from the lake Baikal pelagial. Data obtained by light, scanning, and transmission electron microscopy, along with 16S rRNA gene sequence analysis, allowed the bacterium identification as Trichormus variabilis, previously known as Anabaena variabilis. Trichormus is a cyanobacterial genus not presented in the list of Baikal plankton algae; A. variabilis also hasn’t been previously detected in Baikal phytoplankton. T. variabilis nitrogen fixation ability was demonstrated. The gene responsible for nitrogen fixation, nifH, was identified by PCR and was partially sequenced. No hepatotoxin synthesis genes were revealed in the strain.