Form III RubisCO-mediated transaldolase variant of the Calvin cycle in a chemolithoautotrophic bacterium.

The Calvin-Benson-Bassham (CBB) cycle assimilates CO2 for the primary production of organic matter in all plants and algae, as well as in some autotrophic bacteria. The key enzyme of the CBB cycle, ribulose-bisphosphate carboxylase/oxygenase (RubisCO), is a main determinant of de novo organic matter production on Earth. Of the three carboxylating forms of RubisCO, forms I and II participate in autotrophy, and form III so far has been associated only with nucleotide and nucleoside metabolism. Here, we report that form III RubisCO functions in the CBB cycle in the thermophilic chemolithoautotrophic bacterium Thermodesulfobium acidiphilum, a phylum-level lineage representative. We further show that autotrophic CO2 fixation in T. acidiphilum is accomplished via the transaldolase variant of the CBB cycle, which has not been previously demonstrated experimentally and has been considered unlikely to occur. Thus, this work reveals a distinct form of the key pathway of CO2 fixation.

Metabolic Diversity and Evolutionary History of the Archaeal Phylum "Candidatus Micrarchaeota" Uncovered from a Freshwater Lake Metagenome.

Acidophilic archaea of the archaeal Richmond Mine acidophilic nanoorganisms (ARMAN) group from the uncultured candidate phylum "Candidatus Micrarchaeota" have small genomes and cell sizes and are known to be metabolically dependent and physically associated with their Thermoplasmatales hosts. However, phylogenetically diverse "Ca Micrarchaeota" are widely distributed in various nonacidic environments, and it remains uncertain because of the lack of complete genomes whether they are also devoted to a partner-dependent lifestyle. Here, we obtained nine metagenome-assembled genomes of "Ca Micrarchaeota" from the sediments of a meromictic freshwater lake, including a complete, closed 1.2 Mbp genome of "Ca Micrarchaeota" Sv326, an archaeon phylogenetically distant from the ARMAN lineage. Genome analysis revealed that, contrary to ARMAN "Ca Micrarchaeota," the Sv326 archaeon has complete glycolytic pathways and ATP generation mechanisms in substrate phosphorylation reactions, the capacities to utilize some sugars and amino acids as substrates, and pathways for de novo nucleotide biosynthesis but lacked an aerobic respiratory chain. We suppose that Sv326 is a free-living scavenger rather than an obligate parasite/symbiont. Comparative analysis of "Ca Micrarchaeota" genomes representing different order-level divisions indicated that evolution of the "Ca Micrarchaeota" from a free-living "Candidatus Diapherotrites"-like ancestor involved losses of important metabolic pathways in different lineages and gains of specific functions in the course of adaptation to a partner-dependent lifestyle and specific environmental conditions. The ARMAN group represents the most pronounced case of genome reduction and gene loss, while the Sv326 lineage appeared to be rather close to the ancestral state of the "Ca Micrarchaeota" in terms of metabolic potential.IMPORTANCE The recently described superphylum DPANN includes several phyla of uncultivated archaea with small cell sizes, reduced genomes, and limited metabolic capabilities. One of these phyla, "Ca Micrarchaeota," comprises an enigmatic group of archaea found in acid mine drainage environments, the archaeal Richmond Mine acidophilic nanoorganisms (ARMAN) group. Analysis of their reduced genomes revealed the absence of key metabolic pathways consistent with their partner-associated lifestyle, and physical associations of ARMAN cells with their hosts were documented. However, "Ca Micrarchaeota" include several lineages besides the ARMAN group found in nonacidic environments, and none of them have been characterized. Here, we report a complete genome of "Ca Micrarchaeota" from a non-ARMAN lineage. Analysis of this genome revealed the presence of metabolic capacities lost in ARMAN genomes that could enable a free-living lifestyle. These results expand our understanding of genetic diversity, lifestyle, and evolution of "Ca Micrarchaeota."

Bacterial Communities in Areas of Oil and Methane Seeps in Pelagic of Lake Baikal.

We have assessed the diversity of bacteria near oil-methane (area I) and methane (area II) seeps in the pelagic zone of Lake Baikal using massive parallel sequencing of 16S rRNA, pmoA, and mxaF gene fragments amplified from total DNA. At depths from the surface to 100 m, sequences belonging to Cyanobacteria dominated. In the communities to a depth of 200 m of the studied areas, Proteobacteria dominated the deeper layers of the water column. Alphaproteobacteria sequences were predominant in the community near the oil-methane seep, while the community near the methane seep was characterized by the prevalence of Alpha- and Gammaproteobacteria. Among representatives of these classes, type I methanotrophs prevailed in the 16S rRNA gene libraries from the near-bottom area, and type II methanotrophs were detected in minor quantities at different depths. In the analysis of the libraries of the pmoA and mxaF functional genes, we observed the different taxonomic composition of methanotrophic bacteria in the surface and deep layers of the water column. All pmoA sequences from area I were type II methanotrophs and were detected at a depth of 300 m, while sequences of type I methanotrophs were the most abundant in deep layers of the water column of area II. All mxaF gene sequences belonged to Methylobacterium representatives. Based on comparative analyses of 16S rRNA, pmoA, and mxaF gene fragment libraries, we suggest that there must be a wider spectrum of functional genes facilitating methane oxidation that were not detected with the primers used.

Isolation, characterization, and genome insights into an anaerobic sulfidogenic Tissierella bacterium from Cu-bearing coins.

Recent reports on antimicrobial effects of metallic Cu prompted this study of anaerobic microbial communities on copper surfaces. Widely circulating copper-containing coinage was used as a potential source for microorganisms that had had human contact and were tolerant to copper. This study reports on the isolation, characterization, and genome of an anaerobic sulfidogenic Tissierella sp. P1from copper-containing brass coinage. Dissimilatory (bi)sulfite reductase dsrAB present in strain P1 genome and the visible absorbance around 630 nm in the cells suggested the presence of a desulfoviridin-type protein. However, the sulfate reduction rate measurements with 35SO42- did not confirm the dissimilatory sulfate reduction by the strain. The P1 genome lacks APS reductase, sulfate adenylyltransferase, DsrC, and DsrMK necessary for dissimilatory sulfate reduction. The isolate produced up to 0.79 mM H2S during growth, possibly due to cysteine synthase (CysK) and/or cysteine desulfhydrase (CdsH) activities, encoded in the genome. The strain can tolerate up to 2.4 mM Cu2+(150 mg/l) in liquid medium, shows affinity to metallic copper, and can survive on copper-containing coins up to three days under ambient air and dry conditions. The genome sequence of strain P1 contained cutC, encoding a copper resistance protein, which distinguishes it from all other Tissierella strains with published genomes.

Proteinivorax hydrogeniformans sp. nov., an anaerobic, haloalkaliphilic bacterium fermenting proteinaceous compounds with high hydrogen production.

A search for the organisms responsible for the degradation of biomass of primary producers in Tanatar lakes resulted in the isolation of a novel anaerobic, haloalkaliphilic microorganism, strain Z-710T. The strain grows on proteinaceous substrates (peptides) but not on proteins. A rather limited range of substances of other classes can be utilised together with tryptone but not individually. An interesting physiological feature of the novel strain is a high capacity for hydrogen production (up to 30% v/v) during proteolytic fermentation. Phylogenetic analysis based on the 16S rRNA gene sequence similarity revealed that the organism can be assigned to the previously described genus Proteinivorax. According to its physiological features and the low DNA-DNA hybridisation level of the strain with the type strain of the only previously described Proteinivorax species-Proteinivorax tanatarense Z-910T-strain Z-710T is described here as representing a novel species with the name Proteinivorax hydrogeniformans sp. nov. The type strain is Z-710T (= DSM 102085T = VKM B-3042T).

Microbial processes of the carbon and sulfur cycles in an ice-covered, iron-rich meromictic lake Svetloe (Arkhangelsk region, Russia).

Biogeochemical, isotope geochemical and microbiological investigation of Lake Svetloe (White Sea basin), a meromictic freshwater was carried out in April 2014, when ice thickness was ∼0.5 m, and the ice-covered water column contained oxygen to 23 m depth. Below, the anoxic water column contained ferrous iron (up to 240 µµM), manganese (60 µM), sulfide (up to 2 µM) and dissolved methane (960 µM). The highest abundance of microbial cells revealed by epifluorescence microscopy was found in the chemocline (redox zone) at 23-24.5 m. Oxygenic photosynthesis exhibited two peaks: the major one (0.43 µmol C L-1  day-1 ) below the ice and the minor one in the chemocline zone, where cyanobacteria related to Synechococcus rubescens were detected. The maximum of anoxygenic photosynthesis (0.69 µmol C L-1  day-1 ) at the oxic/anoxic interface, for which green sulfur bacteria Chlorobium phaeoclathratiforme were probably responsible, exceeded the value for oxygenic photosynthesis. Bacterial sulfate reduction peaked (1.5 µmol S L-1  day-1 ) below the chemocline zone. The rates of methane oxidation were as high as 1.8 µmol CH4  L-1  day-1 at the oxi/anoxic interface and much lower in the oxic zone. Small phycoerythrin-containing Synechococcus-related cyanobacteria were probably involved in accumulation of metal oxides in the redox zone.

Microbial diversity and autotrophic activity in Kamchatka hot springs.

Microbial communities of Kamchatka Peninsula terrestrial hot springs were studied using molecular, radioisotopic and cultural approaches. Analysis of 16S rRNA gene fragments performed by means of high-throughput sequencing revealed that aerobic autotrophic sulfur-oxidizing bacteria of the genus Sulfurihydrogenibium (phylum Aquificae) dominated in a majority of streamers. Another widely distributed and abundant group was that of anaerobic bacteria of the genus Caldimicrobium (phylum Thermodesulfobacteria). Archaea of the genus Vulcanisaeta were abundant in a high-temperature, slightly acidic hot spring, where they were accompanied by numerous Nanoarchaeota, while the domination of uncultured Thermoplasmataceae A10 was characteristic for moderately thermophilic acidic habitats. The highest rates of inorganic carbon assimilation determined by the in situ incubation of samples in the presence of 14C-labeled bicarbonate were found in oxygen-dependent streamers; in two sediment samples taken from the hottest springs this process, though much weaker, was found to be not dependent on oxygen. The isolation of anaerobic lithoautotrophic prokaryotes from Kamchatka hot springs revealed a wide distribution of the ability for sulfur disproportionation, a new lithoautotrophic process capable to fuel autonomous anaerobic ecosystems.

Microbial life in Bourlyashchy, the hottest thermal pool of Uzon Caldera, Kamchatka.

Bourlyashchy is the largest and hottest pool in the Uzon Caldera, located in the territory of Kronotsky Nature Reserve, Kamchatka, Russia, with sediment surface temperatures at the margins ranging from 86 to 97 °C, and pH from 6.0 to 7.0. The microbial communities of the pool water and sediments were studied comprehensively from 2005 to 2014. Radioisotopic tracer studies revealed the processes of inorganic carbon assimilation, sulfate reduction, lithotrophic methanogenesis and potentially very active process of acetate oxidation to CO2. The total number of microbial cells in water was different in different years ranging from 5.2 to 7.0 × 10(6); in sediments, it changed from year to year between 6.3 × 10(6) and 1.75 × 10(8), increasing with a decrease in temperature. FISH with Archaea- and Bacteria-specific probes showed that the share of Bacteria differed with year, changing from 34 to 71%. According to 16S rRNA gene pyrosequencing data, lithoautotrophs (Aquificales and Thermoproteales) predominated in water samples, while in sediments they shared the niche with organotrophic Crenarchaeota, Korarchaeota, and bacteria of the genus Caldimicrobium (phylum Thermodesulfobacteria). The majority of organisms in water belonged to cultivated orders of prokaryotes; the only large uncultured group was that representing a novel order in class Thermoprotei. In sediments, unclassified Aquificeae comprised a significant part of the bacterial population. Thus, we showed that the hottest of the terrestrial hot pools studied contains numerous and active microbial populations where Bacteria represent a significant part of the microbial community, and planktonic and sediment populations differ in both composition and function.

Gammaproteobacterial methanotrophs dominate cold methane seeps in floodplains of West Siberian rivers.

A complex system of muddy fluid-discharging and methane (CH4)-releasing seeps was discovered in a valley of the river Mukhrinskaya, one of the small rivers of the Irtysh Basin, West Siberia. CH4 flux from most (90%) of these gas ebullition sites did not exceed 1.45 g CH4 h(-1), while some seeps emitted up to 5.54 g CH4 h(-1). The δ(13)C value of methane released from these seeps varied between -71.1 and -71.3‰, suggesting its biogenic origin. Although the seeps were characterized by low in situ temperatures (3.5 to 5°C), relatively high rates of methane oxidation (15.5 to 15.9 nmol CH4 ml(-1) day(-1)) were measured in mud samples. Fluorescence in situ hybridization detected 10(7) methanotrophic bacteria (MB) per g of mud (dry weight), which accounted for up to 20.5% of total bacterial cell counts. Most (95.8 to 99.3%) methanotroph cells were type I (gammaproteobacterial) MB. The diversity of methanotrophs in this habitat was further assessed by pyrosequencing of pmoA genes, encoding particulate methane monooxygenase. A total of 53,828 pmoA gene sequences of seep-inhabiting methanotrophs were retrieved and analyzed. Nearly all of these sequences affiliated with type I MB, including the Methylobacter-Methylovulum-Methylosoma group, lake cluster 2, and several as-yet-uncharacterized methanotroph clades. Apparently, microbial communities attenuating methane fluxes from these local but strong CH4 sources in floodplains of high-latitude rivers have a large proportion of potentially novel, psychrotolerant methanotrophs, thereby providing a challenge for future isolation studies.

Salinity-induced succession of phototrophic communities in a southwestern Siberian soda lake during the solar activity cycle.

A variety of lakes located in the dry steppe area of southwestern Siberia are exposed to rapid climatic changes, including intra-century cycles with alternating dry and wet phases driven by solar activity. As a result, the salt lakes of that region experience significant fluctuations in water level and salinity, which have an essential impact on the indigenous microbial communities. But there are few microbiological studies that have analyzed this impact, despite its importance for understanding the functioning of regional water ecosystems. This work is a retrospective study aimed at analyzing how solar activity-related changes in hydrological regime affect phototrophic microbial communities using the example of the shallow soda lake Tanatar VI, located in the Kulunda steppe (Altai Region, Russia, southwestern Siberia). The main approach used in this study was the comparison of hydrochemical and microscopic data obtained during annual field work with satellite and solar activity data for the 12-year observation period (2011-2022). The occurrence of 33 morphotypes of cyanobacteria, two key morphotypes of chlorophytes, and four morphotypes of anoxygenic phototrophic bacteria was analyzed due to their easily recognizable morphology. During the study period, the lake surface changed threefold and the salinity changed by more than an order of magnitude, which strongly correlated with the phases of the solar activity cycles. The periods of high (2011-2014; 100-250 g/L), medium (2015-2016; 60 g/L), extremely low (2017-2020; 13-16 g/L), and low (2021-2022; 23-34 g/L) salinity with unique biodiversity of phototrophic communities were distinguished. This study shows that solar activity cycles determine the dynamics of the total salinity of a southwestern Siberian soda lake, which in turn determines the communities and microorganisms that will occur in the lake, ultimately leading to cyclical changes in alternative states of the ecosystem (dynamic stability).

Progress towards elimination of viral hepatitis: a Lancet Gastroenterology & Hepatology Commission update.

The top 20 highest burdened countries (in disability-adjusted life years) account for more than 75% of the global burden of viral hepatitis. An effective response in these 20 countries is crucial if global elimination targets are to be achieved. In this update of the Lancet Gastroenterology & Hepatology Commission on accelerating the elimination of viral hepatitis, we convene national experts from each of the top 20 highest burdened countries to provide an update on progress. Although the global burden of diseases is falling, progress towards elimination varies greatly by country. By use of a hepatitis elimination policy index conceived as part of the 2019 Commission, we measure countries' progress towards elimination. Progress in elimination policy has been made in 14 of 20 countries with the highest burden since 2018, with the most substantial gains observed in Bangladesh, India, Indonesia, Japan, and Russia. Most improvements are attributable to the publication of formalised national action plans for the elimination of viral hepatitis, provision of publicly funded screening programmes, and government subsidisation of antiviral treatments. Key themes that emerged from discussion between national commissioners from the highest burdened countries build on the original recommendations to accelerate the global elimination of viral hepatitis. These themes include the need for simplified models of care, improved access to appropriate diagnostics, financing initiatives, and rapid implementation of lessons from the COVID-19 pandemic.

Halanaerobium polyolivorans sp. nov.-A Novel Halophilic Alkalitolerant Bacterium Capable of Polyol Degradation: Physiological Properties and Genomic Insights.

A search for the microorganisms responsible for the anaerobic degradation of osmoprotectants in soda lakes resulted in the isolation of a novel halophilic and alkalitolerant strain, designated Z-7514T. The cells were Gram-stain-negative and non-endospore-forming rods. Optimal growth occurs at 1.6-2.1 M Na+, pH 8.0-8.5, and 31-35 °C. The strain utilized mainly sugars, low molecular polyols, and ethanolamine as well. The G+C content of the genomic DNA of strain Z-7514T was 33.3 mol%. Phylogenetic and phylogenomic analyses revealed that strain Z-7514T belongs to the genus Halanaerobium. On the basis of phenotypic properties and the dDDH and ANI values with close validly published species, it was proposed to evolve strain Z-7514T within the genus Halanaerobium into novel species, for which the name Halanaerobium polyolivorans sp. nov. was proposed. The type strain was Z-7514T (=KCTC 25405T = VKM B-3577T). For species of the genus Halanaerobium, the utilization of ethylene glycol, propylene glycol, and ethanolamine were shown for the first time. The anaerobic degradation of glycols and ethanolamine by strain Z-7514T may represent a novel metabiotic pathway within the alkaliphilic microbial community. Based on a detailed genomic analysis, the main pathways of catabolism of most of the used substrates have been identified.

A Novel View of the Diversity of Anoxygenic Phototrophic Bacteria Inhabiting the Chemocline of Meromictic Karst Lakes.

The rates of oxygenic and anoxygenic photosynthesis, the microorganisms responsible for these processes, and the hydrochemical characteristics of the sulfide-containing karst lakes, Black Kichier and Big Kichier (Mari El Republic), were investigated. In these lakes, a plate of anoxygenic phototrophic bacteria (APB) is formed at the upper boundary of sulfide occurrence in the water. The phototrophic community of the chemocline zone was analyzed using a combination of high-throughput sequencing of the 16S rRNA gene fragments and light and electron microscopic techniques. Green-colored Chlorobium clathratiforme were absolutely predominant in both lakes. The minor components included green sulfur bacteria (GSB) Chlorobium spp., symbiotic consortia Chlorochromatium magnum and Pelochromatium roseum, purple sulfur bacteria (PSB) Chromatium okenii, and unidentified phylotypes of the family Chromatiaceae, as well as members of the Chloroflexota: Chloronema sp. and Oscillochloris sp. Based on the results of the molecular analysis, the taxonomic status of Ancalochloris perfilievii and other prosthecate GSB, as well as of the PSB Thiopedia rosea, which were visually revealed in the studied freshwater lakes, is discussed.

Biogeochemical Activity of Methane-Related Microbial Communities in Bottom Sediments of Cold Seeps of the Laptev Sea.

Bottom sediments at methane discharge sites of the Laptev Sea shelf were investigated. The rates of microbial methanogenesis and methane oxidation were measured, and the communities responsible for these processes were analyzed. Methane content in the sediments varied from 0.9 to 37 µmol CH4 dm-3. Methane carbon isotopic composition (δ13C-CH4) varied from -98.9 to -77.6‱, indicating its biogenic origin. The rates of hydrogenotrophic methanogenesis were low (0.4-5.0 nmol dm-3 day-1). Methane oxidation rates varied from 0.4 to 1.2 µmol dm-3 day-1 at the seep stations. Four lineages of anaerobic methanotrophic archaea (ANME) (1, 2a-2b, 2c, and 3) were found in the deeper sediments at the seep stations along with sulfate-reducing Desulfobacteriota. The ANME-2a-2b clade was predominant among ANME. Aerobic ammonium-oxidizing Crenarchaeota (family Nitrosopumilaceae) predominated in the upper sediments along with heterotrophic Actinobacteriota and Bacteroidota, and mehtanotrophs of the classes Alphaproteobacteria (Methyloceanibacter) and Gammaproteobacteria (families Methylophilaceae and Methylomonadaceae). Members of the genera Sulfurovum and Sulfurimonas occurred in the sediments of the seep stations. Mehtanotrophs of the classes Alphaproteobacteria (Methyloceanibacter) and Gammaproteobacteria (families Methylophilaceae and Methylomonadaceae) occurred in the sediments of all stations. The microbial community composition was similar to that of methane seep sediments from geographically remote areas of the global ocean.

Treatment and monitoring of children and adolescents with hepatitis C in Russia: Results from a multi-centre survey on policy and practice.

BACKGROUND: The Russian Federation has the largest paediatric hepatitis C virus (HCV) disease burden in the World Health Organization European region with an estimated 118,000 children living with HCV viraemia. Direct-acting antivirals (DAAs) have been available for adults in Russia since 2015 and approved for treatment of adolescents aged ≥12 years since 2019. We evaluated DAA availability and uptake for HCV treatment of children and adolescents and clinical practices on diagnosis and management of paediatric HCV in Russia. METHODS: A survey was distributed to regional ministries of health in 85 administrative regions during September 2020. The survey consisted of 22 items collecting data on: type of facility, aggregate patient characteristics, HCV testing practices for children and pregnant women and HCV management and treatment practices for children. RESULTS: Survey responses were received from 37 of the 85 regions in Russia (response rate 44%). 2159 children and adolescents with chronic HCV were in follow-up; 1089 (50%) were female. Of 2080 children with available data on age-groups, 134 (6%) were <3 years, 336 (16%) 3-<6 years, 718 (35%) 6-<12 years and 892 (43%) 12-<18 years. 134 (15%) of 892 adolescents ≥12 years received DAAs, 96 (72%) glecaprevir/pibrentasvir, 26 (19%) sofosbuvir, 8 (6%) daclatasvir and 4 (3%) sofosbuvir/ledipasvir. CONCLUSIONS: This study provides a baseline of DAA uptake in early stages of rollout for children and adolescents. The use of DAAs for treatment of adolescents in Russia presents a unique opportunity for HCV micro-elimination in this population.

The Baltic Sea methane pockmark microbiome: The new insights into the patterns of relative abundance and ANME niche separation.

Pockmarks are important "pumps", which are believed to play a significant role in the global methane cycling and harboring a unique assemblage of very diverse prokaryotes. This study reports the results of massive sequencing of the 16S rRNA gene V4 hypervariable regions for the samples from thirteen pockmark horizons (the Baltic Sea) collected at depths from 0 to 280 cm below seafloor (cmbsf) and the rates of microbially mediated anaerobic oxidation of methane (AOM) and sulfate reduction (SR). Altogether, 76 bacterial and 12 archaeal phyla were identified, 23 of which were candidate divisions. Of the total obtained in the pockmark sequences, 84.3% of them were classified as Bacteria and 12.4% as Archaea; 3.3% of the sequences were assigned to unknown operational taxonomic units (OTUs). Members of the phyla Planctomycetota, Chloroflexota, Desulfobacterota, Caldatribacteriota, Acidobacteriota and Proteobacteria predominated across all horizons, comprising 58.5% of the total prokaryotic community. These phyla showed different types of patterns of relative abundance. Analysis of AOM-SR-mediated prokaryotes abundance and biogeochemical measurements revealed that ANME-2a-2b subcluster was predominant in sulfate-rich upper horizons (including sulfate-methane transition zone (SMTZ)) and together with sulfate-reducing bacterial group SEEP-SRB1 had a primary role in AOM coupled to SR. At deeper sulfate-depleted horizons ANME-2a-2b shifted to ANME-1a and ANME-1b which alone mediated AOM or switch to methanogenic metabolism. Shifting of the ANME subclusters depending on depth reflect a tendency for niche separation in these groups. It was shown that the abundance of Caldatribacteriota and organohalide-respiring Dehalococcoidia (Chloroflexota) exhibited a strong correlation with AOM rates. This is the first detailed study of depth profiles of prokaryotic diversity, patterns of relative abundance, and ANME niche separation in the Baltic Sea pockmark microbiomes sheds light on assembly of prokaryotes in a pockmark.

Epidemiology and Genotype Distribution of Hepatitis C Virus in Russia.

The hepatitis C virus (HCV) causes both acute and chronic infection of the liver that can lead to liver cirrhosis, cancer, and liver failure. HCV is characterized by high genetic diversity and substantial variations in the prevalence of specific HCV genotypes throughout the world. Many effective regimens of direct-acting antivirals (DAAs), including pan-genotypic, can successfully treat HCV infection. Additionally, genotype-specific treatments for HCV are being actively employed in national plans for eliminating HCV infection around the world. The evaluation of HCV genotype prevalence in a given country is necessary for the successful implementation of the HCV elimination plans and for allocating financial resources to the DAAs which are the most effective against those specific HCV genotypes prevalent in a given country. Here, we analyzed HCV genotypes, subgenotypes, and recombinants in 10,107 serum samples collected in 2015-2017 from patients with chronic HCV infection living in all federal districts of Russia. This is the first and largest evaluation of HCV genotypes performed on samples from all territories of Russia, from its Central federal district to the Far East. Moreover, we have updated retrospective epidemiological analysis of chronic and acute HCV infection in Russia from 2001 to 2021. We demonstrate that the incidence of acute HCV (AHC) infection in Russia decreased from 16.7 cases per 100,000 people in 2001 to 0.6/100,000 in 2021. The number of cases of chronic HCV (CHC) infection also decreased from 29.5 to 16.4 per 100,000 people during this period. The HCV genotype analysis indicated that HCV genotype 1 dominates in Russia (53.6%), while genotypes 3 and 2 were detected in 35.4% and 7.8% of patients, respectively. These proportions are virtually identical in all regions of Russia except for the Far East, where HCV genotype 2 was detected in only 1% of the samples. HCV genotypes 1 and 2 are more widespread in women, and HCV genotype 3 in men. Genotype 3 was the most prevalent in 31-40-year-olds (44.9%), and genotype 1 was most prevalent in those over 70 years of age (72.2%). HCV genotype 2 was predominant among HCV-infected persons older than 40 years. Discriminating between HCV genotype 2 and recombinant RF1_2k/1b, which are frequently misclassified, is important for successful antiviral treatment. For the first time, we demonstrate, here, countrywide prevalence of HCV RF1_2k/1b in different regions of Russia. HCV RF1_2k/1b makes up 3.2% of HCV genotypes, reaching 30% among samples classified as genotype 2 by some commercial genotyping tests. The highest proportion of HCV RF1_2k/1b was detected in the North-West (60%), Southern (41.6%), and Central (31.6%) federal districts; its frequency in the Far Eastern and North Caucasus districts was ~14.3%. HCV RF1_2k/1b, and it was not detected in the Volga, Ural, or Siberian districts. To conclude, this is the first and most complete evaluation of HCV epidemiology and genotype/subgenotype distribution in Russia.

Activity and distribution of thermophilic prokaryotes in hydrothermal fluid, sulfidic structures, and sheaths of alvinellids (East Pacific Rise, 13°N).

Processes of inorganic carbon assimilation, methanogenesis, sulfate reduction, and acetate oxidation to CO(2) occurring in samples from the East Pacific Rise at 13°N were traced, using radioisotopically labeled substrates, at temperatures ranging from 65 to 100°C. Molecular hydrogen stimulated lithotrophic methanogenesis and sulfate reduction but inhibited inorganic carbon assimilation. Active mineralization of acetate was observed in an organic-rich Alvinella-associated system at 80°C. Members of the Thermococcales were the most numerous hyperthermophilic archaea in these samples, their density achieving 10(8) cells per cm(3), while the numbers of cultured hydrogen-utilizing thermophilic lithotrophs were several orders of magnitude lower.

Anaerobic transformation of carbon monoxide by microbial communities of Kamchatka hot springs.

Carbon monoxide (CO) is one of the common gaseous compounds found in hot volcanic environments. It is known to serve as the growth substrate for a number of thermophilic prokaryotes, both aerobic and anaerobic. The goal of this work was to study the process of anaerobic transformation of CO by microbial communities inhabiting natural thermal environments: hot springs of Uzon Caldera, Kamchatka. The anaerobic microbial community of Treshchinny Spring (80°C, pH 6.5) was found to exhibit two peaks of affinity for CO (K (S1) = 54 nM and K (S2) = 1 µM). The actual rate of anaerobic CO transformation by the microbial community of this spring, calculated after obtaining the concentration dependence curve and extrapolated to the natural concentration of CO dissolved in the hot spring water (20 nM), was found to be 120 µmol l(-1) of sediment day(-1). In all the hot springs studied, more than 90% of the carbon of (14)CO upon anaerobic incubation was recovered as (14)CO(2). From 1 to 5% of (14)CO was transformed to volatile fatty acids (VFA). The number of microorganisms capable of anaerobic CO oxidation determined by dilution-to-extinction method reached 10(6) cells ml(-1) of sediment. CO-transforming anaerobic thermophilic microorganisms isolated from the springs under study exhibited hydrogenogenic type of CO oxidation and belonged to the bacterial genera Carboxydocella and Dictyoglomus. These data suggest a significant role of hydrogenogenic carboxydotrophic prokaryotes in anaerobic CO transformation in Uzon Caldera hot springs.

Diversity and Activity of Sulfate-Reducing Prokaryotes in Kamchatka Hot Springs.

Microbial communities of the Kamchatka Peninsula terrestrial hot springs were studied using radioisotopic and cultural approaches, as well as by the amplification and sequencing of dsrB and 16S rRNA genes fragments. Radioisotopic experiments with 35S-labeled sulfate showed that microbial communities of the Kamchatka hot springs are actively reducing sulfate. Both the cultivation experiments and the results of dsrB and 16S rRNA genes fragments analyses indicated the presence of microorganisms participating in the reductive part of the sulfur cycle. It was found that sulfate-reducing prokaryotes (SRP) belonging to Desulfobacterota, Nitrospirota and Firmicutes phyla inhabited neutral and slightly acidic hot springs, while bacteria of phylum Thermodesulofobiota preferred moderately acidic hot springs. In high-temperature acidic springs sulfate reduction was mediated by archaea of the phylum Crenarchaeota, chemoorganoheterotrophic representatives of genus Vulcanisaeta being the most probable candidates. The 16S rRNA taxonomic profiling showed that in most of the studied communities SRP was present only as a minor component. Only in one microbial community, the representatives of genus Vulcanisaeta comprised a significant group. Thus, in spite of comparatively low sulfate concentrations in terrestrial hot springs of the Kamchatka, phylogenetically and metabolically diverse groups of sulfate-reducing prokaryotes are operating there coupling carbon and sulfur cycles in these habitats.