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Investigations were carried out to study the process of sulfate reduction in freshwater lake Nazarovskoye (Konoshsky district, Arkhangelsk region). Field work was carried out in the winter (March) and summer (July) seasons from 2013 to 2017. Biogeochemical parameters (content of sulfates, iron, organic matter, sulfur forms) and the speed of the bacterial sulfate reduction process in the selected samples were determined using conventional or approved methods. The water in the lake was characterized as fresh, bicarbonate class of calcium group. In the water column, the maximum amounts of sulfates 107 mg/L and hydrogen sulfide 1355 μg / L were noted in the winter. In the bottom sediments of the lake, more intensive sulfate reduction occurred in the summer period (maximum process speed was 555 μg S/dm3 per day). In contrast to the majority of previously studied freshwater lakes in Arkhangelsk region, this reservoir had the highest concentrations of sulfates and hydrogen sulfide in water. At the same time, the lowest speed of the bacterial process of sulfate reduction both in water and bottom sediments was recorded. However, among the derivatives of hydrogen sulfide in bottom sediments, pyrite sulfur dominated among sulfide compounds in Lake Nazarovskoe, which may indirectly indicate a fairly active process of sulfate reduction in the sediments of this shallow reservoir. It can be assumed that despite the high speed of the process, in the summer the sulfide compounds formed in the upper layers of the sediments can be oxidized due to the penetration of oxygen to the bottom of the reservoir via the small depth of the lake; and in the winter compounds of reduced sulfur are accumulated in the bottom sediments (anaerobic conditions are noted even in the water column of the reservoir).

Following the WHO announcement of smallpox eradication, discontinuation of smallpox vaccination with vaccinia virus (VACV) was recommended. However, interest in VACV was soon renewed due to the opportunity of genetic engineering of the viral genome by directed insertion of foreign genes or introduction of mutations or deletions into selected viral genes. This genomic technology enabled production of stable attenuated VACV strains producing antigens of various infectious agents. Due to an increasing threat of human orthopoxvirus re-emergence, the development of safe highly immunogenic live orthopoxvirus vaccines using genetic engineering methods has been the challenge in recent years. In this study, we investigated an attenuated VACV LIVP-GFP (TK-) strain having an insertion of the green fluorescent protein gene into the viral thymidine kinase gene, which was generated on the basis of the LIVP (Lister-Institute for Viral Preparations) strain used in Russia as the first generation smallpox vaccine. We studied the effect of A34R gene modification and A35R gene deletion on the immunogenic and protective properties of the LIVP-GFP strain. The obtained data demonstrate that intradermal inoculation of the studied viruses induces higher production of VACV-specific antibodies compared to their levels after intranasal administration. Introduction of two point mutations into the A34R gene, which increase the yield of extracellular enveloped virions, and deletion of the A35R gene, the protein product of which inhibits presentation of antigens by MHC II, enhances protective potency of the created LIVP-TK--A34R*-dA35R virus against secondary lethal orthopoxvirus infection of BALB/c mice even at an intradermal dose as low as 103 plaque forming units (PFU)/mouse. This virus may be considered not only as a candidate attenuated live vaccine against smallpox and other human orthopoxvirus infections but also as a vector platform for development of safe multivalent live vaccines against other infectious diseases using genetic engineering methods.

Meromictic lakes are a unique model for the study of the anaerobic processes of organic matter degradation, such as methanogenesis and sulphate reduction. As a result of activity of sulfate-reducing bacteria hydrogen sulfide accumulates in monimolimnion of these lakes, whereas chemocline is the area of sharp vertical gradients of physical and chemical conditions and as a consequence is the ecological niche for different planktonic microorganisms. This paper describes some characteristics of meromictic freshwater Lake Svetloe, located in the north of the Arkhangelsk region, for which iron-manganese type of meromixia was defined. The distribution of the studied parameters corresponds to the distribution of the specific for meromictic lakes water layers formed in the presence of stable stratification. In the transition layer (chemocline) a sharp decrease in the oxygen content (almost to the analytical zero) is accompanied by an equally sharp increase in the value of the water conductivity and the emergence of dissolved hydrogen sulfide in the water. In the anaerobic zone the conductivity values remain high and accumulation of nutrients, iron, manganese, and hydrogen sulphide (average 30 mg/l) occurs. Besides, the significant decrease in the content of dissolved sulphate caused by its consumption by sulfate-reducing bacteria was noted in this layer. The number of sulphate-reducing bacteria in the water column during the time of observation varied in the range of 10 – 106 cells/ml with the highest content in the chemocline zone, where the maximum amounts of hydrogen sulphide (up to 130 mg/l) were also found

We consider the peculiarities of the process of sulfate reduction in three freshwater lakes with different anthropogenic impacts and groundwater types. Quantitative indicators of this process are presented. The results obtained are compared and the features of sulfate reduction in each of the reservoirs are highlighted. It is shown that the intensive sulfate reduction in water in summer is recorded for the most anthropogenically loaded lake. For a reservoir with the receipt of a sulfate type of groundwater, the process proceeds with the greatest accumulation of reduced sulfur compounds both in water and in bottom sediments.