Microbial and Monosaccharide Composition of Biofilms Developing on Sandy Loams from an Aquifer Contaminated with Liquid Radioactive Waste.

The development of microbial biofilms increases the survival of microorganisms in the extreme conditions of ecosystems contaminated with components of liquid radioactive waste (LRW) and may contribute to the successful bioremediation of groundwater. The purpose of this work was to compare the composition of the microorganisms and the exopolysaccharide matrix of the biofilms formed on sandy loams collected at the aquifer from a clean zone and from a zone with nitrate and radionuclide contamination. The aquifer is polluted from the nearby surface repository for liquid radioactive waste (Russia). The phylogenetic diversity of prokaryotes forming biofilms on the sandy loams' surface was determined during 100 days using high-throughput sequencing of the V4 region of the 16S rRNA genes. Scanning electron microscopy was used to study the development of microbial biofilms on the sandy loams. The ratio of proteins and carbohydrates in the biofilms changed in the course of their development, and the diversity of monosaccharides decreased, depending on the contamination of the sites from which the rocks were selected. The presence of pollution affects biofilm formation and EPS composition along with the dominant taxa of microorganisms and their activity. Biofilms establish a concentration gradient of the pollutant and allow the microorganisms involved to effectively participate in the reduction of nitrate and sulfate; they decrease the risk of nitrite accumulation during denitrification and suppress the migration of radionuclides. These biofilms can serve as an important barrier in underground water sources, preventing the spread of pollution. Pure cultures of microorganisms capable of forming a polysaccharide matrix and reducing nitrate, chromate, uranyl, and pertechnetate ions were isolated from the biofilms, which confirmed the possibility of their participation in the bioremediation of the aquifer from nonradioactive waste components and the decrease in the radionuclides' migration.

Structure elucidation and gene cluster annotation of the O-antigen of Pseudomonas veronii SHC-8-1 containing 2-acetamido-2,4,6-trideoxy-4-(3,5-dihydroxyhexanoylamino)-d-glucose.

O-polysaccharide (O-antigen, OPS) was isolated from the lipopolysaccharide of Pseudomonas veronii SHC-8-1 and studied by component analyses and 1D and 2D NMR spectroscopy. The following structure of the O-polysaccharide was established: where QuipNAc4N(dHh) is 2,4-diamino-2,4,6-trideoxy-dglucose (Bacillosamine) in which N-2 is acetylated and N-4 is acylated with 3,5-dihydroxyhexanoic acid (dHh). The O-antigen gene cluster of Pseudomonas veronii SHC-8-1 has been sequenced. The gene functions were tentatively assigned by comparison with sequences in the available databases and found to be in agreement with the OPS structure.

5,5-Di-chloro-6-hy-droxy-dihydro-pyrimidine-2,4(1H,3H)-dione: mol-ecular and crystal structure, Hirshfeld surface analysis and the new route for synthesis with Mg(ReO4)2 as a new catalyst.

The mol-ecular and crystal structures of the title compound, C4H4Cl2N2O3, were investigated by single-crystal X-ray diffraction and a Hirshfeld surface analysis. The title compound was synthesized by a new type of reaction using Mg(ReO4)2 as a new catalyst and a possible mechanism for this reaction is proposed. The six-membered ring adopts a half-chair conformation. In the crystal, hydrogen bonds connect the mol-ecules into double layers, which are connected to each other by halogen bonds. The Hirshfeld surface analysis revealed that the most important contributions for the crystal packing are from O⋯H/H⋯O (35.8%), Cl⋯Cl (19.6%), Cl⋯H/H⋯Cl (17.0%), H⋯H (8.3%), C⋯O/O⋯C (4.3%), Cl⋯O/O⋯Cl (4.2%) and O⋯O (4.1%) contacts.

Structure and gene cluster of the O-polysaccharide from Pseudomonas veronii A-6-5 and its uranium bonding.

A denitrifying bacterium Pseudomonas veronii A-6-5 was isolated from a deep aquifer contaminated with nitrates and uranium. The O-polysaccharide (OPS) was isolated by mild acid degradation of the lipopolysaccharide of P. veronii A-6-5 and studied using sugar analysis and 1D and 2D 1H and 13C NMR spectroscopy. The trisaccharide O-repeating unit was found to have the following structure: [Formula: see text] [Formula: see text] where Hb is 3-hydroxybutanoyl. The genome of P. veronii A-6-5 was sequenced and a respective OPS gene cluster was identified. Functions of the proteins encoded in the gene cluster, including the enzymes involved in the O-polysaccharide biosynthesis and glycosyl transferases, were putatively assigned by comparison with available database sequences. Formation of a new coordination bond between uranyl and the O-polysaccharide from P. veronii A-6-5 was demonstrated using FTIR spectroscopy; it may affect uranyl migration in the groundwaters due to its immobilization on microbial biofilms. Applied importance of this work is that the structure of the O-polysaccharide of a strain isolated from uranium-contaminated groundwater was determined and the character of interaction between the polysaccharide and the uranyl ion was established. The data obtained are of importance for development of the biotechnologies for treatment of uranium-contaminated groundwater and activated sludge.

Microbial Community and in situ Bioremediation of Groundwater by Nitrate Removal in the Zone of a Radioactive Waste Surface Repository.

The goal of the present work was to investigate the physicochemical and radiochemical conditions and the composition of the microbial community in the groundwater of a suspended surface repository for radioactive waste (Russia) and to determine the possibility of in situ groundwater bioremediation by removal of nitrate ions. Groundwater in the repository area (10-m depth) had elevated concentrations of strontium, tritium, nitrate, sulfate, and bicarbonate ions. High-throughput sequencing of the V3-V4/V4 region of the 16S rRNA gene revealed the presence of members of the phyla Proteobacteria (genera Acidovorax, Simplicispira, Thermomonas, Thiobacillus, Pseudomonas, Brevundimonas, and uncultured Oxalobacteraceae), Firmicutes (genera Bacillus and Paenibacillus), and Actinobacteria (Candidatus Planktophila, Gaiella). Canonical correspondence analysis suggested that major contaminant - nitrate, uranium, and sulfate shaped the composition of groundwater microbial community. Groundwater samples contained culturable aerobic organotrophic, as well as anaerobic fermenting, iron-reducing, and denitrifying bacteria. Pure cultures of 33 bacterial strains belonging to 15 genera were isolated. Members of the genera Pseudomonas, Rhizobium, Cupriavidus, Shewanella, Ensifer, and Thermomonas reduced nitrate to nitrite and/or dinitrogen. Application of specific primers revealed the nirS and nirK genes encoding nitrite reductases in bacteria of the genera Pseudomonas, Rhizobium, and Ensifer. Nitrate reduction by pure bacterial cultures resulted in decreased ambient Eh. Among the organic substrates tested, sodium acetate and milk whey were the best for stimulation of denitrification by the microcosms with groundwater microorganisms. Injection of these substrates into the subterranean horizon (single-well push-pull test) resulted in temporary removal of nitrate ions in the area of the suspended radioactive waste repository and confirmed the possibility for in situ application of this method for bioremediation.

Draft Genome Sequence of a Dissimilatory U(VI)-Reducing Bacterium, Shewanella xiamenensis Strain DCB2-1, Isolated from Nitrate- and Radionuclide-Contaminated Groundwater in Russia.

Here, we describe the draft genome sequence of Shewanella xiamenensis strain DCB2-1, isolated from nitrate- and radionuclide-contaminated groundwater. This strain is able to reduce nitrate, Tc(VII), Cr(VI), Fe(III), and U(VI), and its genome sequence contains several gene sets encoding denitrification, resistance to heavy metals, and reduction of metals and metalloids.