Improving the level of water quality and plant species diversity in the reservoir accumulating natural effluents from the reclaimed uranium-containing industrial waste dump.

Due to the need to achieve the principles of sustainable development and to understand the processes of formation of phytocenoses in areas that were adversely affected by the industrial impact, this study assessed the condition of the Grachevsky uranium mine (Kazakhstan), which underwent conservation procedures about 25 years ago. The purpose is to determine the level of water quality and phytocenosis of the shores of the reservoir accumulating natural effluents from reclaimed dumps and anthropogenic sites of a uranium mine, as well as quality indicators and toxicology. The assessment included a qualitative research method (analysis of documents) to determine agro-climatic conditions and empirical methods of collecting information. The authors studied the intensity of ionizing radiation of the gamma background of the water surface of the reservoir (and sections of the shoreline and territories adjacent to the reservoir), and hydrochemical parameters of the waters of the reservoir, and performed a description of the botanical diversity. The vegetation cover of the sections of the reservoir shore is at different stages of syngenesis and is represented by pioneer groupings, group thicket communities, and diffuse communities. Favorable ecological conditions for the settlement and development of plants develop within the shores of the reservoir. The intensity levels of ionizing radiation do not exceed the maximum permissible levels and practically do not affect the formation of phytocenoses. An anthropogenically modified dry meadow with the participation of plants typical of the steppe zone has been formed on the floodplain terrace. Concerning the indicators of quality and toxicology of this reservoir, the water can be used for household and drinking purposes under the condition of prior water treatment. It can be concluded that a high level of natural purification of the reservoir waters occurred within twenty years after the reclamation of the uranium mine.

Electrochemical Characteristics of the Oxidation of Sulfur- and Iron-Containing Compounds by Acidophilic Microorganisms.

The electrochemical features of the interactions of sulfur- and iron-containing compounds (ferrous sulfate, elemental sulfur, pyrite tailings, cysteine, sodium thiosulfate) with a model acidophilic consortium, including the genera Leptospirillum, Sulfobacillus, Acidithiobacillus, Ferroplasma, and Acidiplasma, were studied. The method of cyclic voltammetry recorded redox processes at the electrode/solution interface in the presence of the studied sulfur- and iron-containing compounds. In general, the modeling consortium led to the intensification of these processes. The characteristics of the diffuse layer near the electrode/solution interface were studied using electrochemical impedance spectroscopy. The introduction of microorganisms and/or substrates into the supporting electrolyte led to a decrease in the slope and can be interpreted as evidence of their effect on the diffusion part of the double layer. Its contribution decreases in favor of ion transport. All this, in general, does not contradict the assumption of cell adsorption on the electrode surface. Confocal laser scanning microscopy confirmed this assumption and showed cell adhesion to the surface. The data obtained confirm the importance of bioelectrochemical processes of the studied group of microorganisms in biotechnological processes associated with the leaching of metals from sulfide ores.

Genome analysis of Acidiplasma sp. MBA-1, a polyextremophilic archaeon predominant in the microbial community of a bioleaching reactor.

Results of genome analysis of a member of the family Ferroplasmaceae, Acidiplasma sp. strain MBA-1, an extremely acidophilic, moderately thermophilic archaeon oxidizing ferrous iron under oxic conditions and utilizing organic compounds. This strain was previously shown to predominate in the community carrying out biooxidation of pyrite-arsenopyrite gold-bearing concentrate. The genome was sequenced using the Illumina HiSeq 2000 platform. A total of 2306800 pairwise reads were obtained, corresponding to 300-fold coverage. Assembly was carried out by three programs in parallel. The optimal assembly contained nine contigs, the genome size was 1747364 bp, and N50 was 446845 bp. Annotation of the genome revealed 1749 protein-encoding sequences, as well as 46 tRNA genes and one rRNA gene copy. The results of genome analysis confirmed the previous data on the physiology of this organism. The gene of sulfocyanin (TZ01_06185), a blue copper-containing protein playing the key role in the iron-oxidizing electron transport chain, was identified in the genome. The genes encoding sulfur oxidoreductase (TZ01_04750) and sulfateadenilyl transferase (TZ01_04545), the enzymes of sulfur oxidation, were also identified. The genes involved in the transport and catabolism of organic compounds and the genes of the 3-hydroxypropionate/4-hydroxybutyrate cycle were revealed. The genome of Acidiplasma sp. MBA-1 is the first genome of this genus deposited to a public database DDBJ/EMBL/GenBank (accession no. JYHS00000000) and is of interest for further investigation of Acidiplasma archaea.

[Biooxidation of gold-bearing sulfide ore and subsequent biological treatment of cyanidation residues].

The percolation biooxidation parameters of ore from the Bakyrchik deposit were studied. An investigation of the technological parameters (such as the concentration of leaching agents, irrigation intensity, and pauses at various stages of the leaching) revealed the optimal mode for precious metal extraction. The stages of the ore processing were biooxidation, gold extraction by cyanidation or thiosulfate leaching, and biological destruction of cyanide. The gold and silver recovery rates by cyanidation were 64.0 and 57.3%, respectively. The gold and silver recovery rates by thiosulfate leaching were 64.0 and 57.3%, respectively. Gold and silver recovery rates from unoxidized ore (control experiment) by cyanidation were 20.9 and 26.8%, respectively. Thiosulfate leaching of unoxidized ore allowed the extraction of 38.8 and 24.2% of the gold and silver, respectively. Cyanidation residues were treated with bacteria of the genus Alcaligenes in order to destruct cyanide.

[Leaching of Rare Earth Elements from Coal Ashes Using Acidophilic Chemolithotrophic Microbial Communities].

A method for leaching rare earth elements from coal ash in the presence of elemental sulfur using communities of acidophilic chemolithotrophic microorganisms was proposed. The optimal parameters determined for rare element leaching in reactors were as follows: temperature, 45 degrees C; initial pH, 2.0; pulp density, 10%; and the coal ash to elemental sulfur ratio, 10 : 1. After ten days of leaching, 52.0, 52.6, and 59.5% of scandium, yttrium, and lanthanum, respectively, were recovered.

[Physiological Properties of Acidithiobacillus ferrooxidans Strains Isolated from Sulfide Ore Deposits in Kazakhstan].

Acidithiobacillus ferroxidans strains were isolated from acidophilic microbial communities of Kazakhstan sulfide ore deposits. Their biotechnologically important properties (optimal and maximal growth temperatures and resistance to NaCl) were determined. While temperature optima of the strains were the same (30-32 degrees C), temperature ranges were different. Thus, strain TFBK oxidized iron very poorly at 37 degrees C, while for strain TFV, the iron oxidation rate at this temperature was insignificantly lower than at lesser temperatures. NaCl inhibited the oxidative activity of both strains. Iron oxidation by strain TFV was inhibited at 5 g/L NaCl and was suppressed almost completely at 20 g/L. Iron oxidation by strain TFBK was inhibited by NaCl to a lesser degree, so that iron oxidation rate was relatively high at 10 g/L, while at 20 g/L NaCl the process was not suppressed completely, although the oxidation rate was low. Sulfur oxidation by these strains was less affected by NaCl than oxidation of ferrous iron. Sulfur oxidation by strain TFV was considerably inhibited only at 20 g/L NaCl, but was not suppressed completely. Sulfur oxidation by strain TFBK was more affected by NaCl. At 10 g/L NaCl the oxidation rate was much lower than at lower NaCl concentrations (sulfate concentrations after 6 days of oxidation at 5 and 10 g/L NaCl were -130 and -100 mM, respectively). While sulfur oxidation by strain TFBK was considerably inhibited at 10 and 20 g/L NaCl, similar to strain TFV it was not suppressed completely. Our results indicate the adaptation of the species A. ferrooxidans to a broad range of growth conditions.

[Biooxidation of a Double-Refractory Gold-Bearing Sulfide Ore Concentrate].

The efficiency of biooxidation for treatment of a double-refractory gold-bearing sulfide ore concentrate from the Bakyrchik deposit (East Kazakhstan) was defined. The experiments were conducted in two different modes, i.e., with the standard liquid medium and the medium imitating the chemical composition of the Bakyrchik deposit groundwater and containing high concentrations of sodium, magnesium, and chloride. The concentrate contained 17.5% of organic carbon, 6% of pyrite and 13% arsenopyrite. Gold content was 57.5 g t@-1@. Direct gold recovery by cyanidation was very low (2.8%). While biooxidation was efficient in both cases (approximately 90% of sulfide sulfur was oxidized), the efficiency of cyanidation was low (39 and 32%, respectively). This fact suggests high efficiency of biooxidation is insufficient for efficient treatment of double-refractory gold-bearing sulfide ore concentrates.

[Selection of a community of acidochemolithotrophic microorganisms with a high oxidation rate of pyrrhotite- containing sulphide ore flotatation concentrate].

A community of acidochemolithotrophic microorganisms with a high oxidation rate of pyrrhotite-containing sulphide ore flotation concentrate was selected. The Acidithiobacillus caldus OP-1 and Ferroplasma acidiphilum OP-2 cultures were identified to be dominating members. The presence of the Acidithio- bacillusferrooxidans OP-3, Leptospirillumferriphilum OP-4, and Sulfobacillus thermosulfidooxidans OP-5 cultures in the community's composition was also mentioned. The analysis results of solid residues of the process showed a greater elemental sulfur oxidation level and gold recovery when the initial pH value in tank I was maintained at a level of 1.8-2.0 (90.5%) rather than 1.6-1.8 (86.3%).

[Oxidation of sulfur-containing substrates by aboriginal and experimentally designed microbial communities].

Aboriginal and experimental (constructed of pure microbial cultures) communities of acidophilic chemolithotrophs have been studied. The oxidation of elemental sulfur, sodium thiosulfate, and potassium tetrathionate as sole sources of energy has been monitored. The oxidation rate of the experimental community is higher as compared to the aboriginal community isolated from a flotation concentrate of pyrrhotine-containing pyrite-arsenopyrite gold-arsenic sulfide ore. The degree of oxidation of the mentioned S substrates amounts to 17.91, 68.30, and 93.94% for the experimental microbial community and to 10.71, 56.03, and 79.50% for the aboriginal community, respectively. The degree of oxidation of sulfur sulfide forms in the ore flotation concentrate is 59.15% by the aboriginal microbial community and 49.40% by the experimental microbial community. Despite a higher rate of oxidation of S substrates as a sole source of energy by the experimental microbial community, the aboriginal community oxidizes S substrates at a higher rate in the flotation concentrate of pyrrhotine-containing pyrite-arsenopyrite gold-arsenic sulfide ore, from which it was isolated. Bacterial-chemical oxidation of the flotation concentrate by the aboriginal microbial community allows for the extraction of an additional 32.3% of gold from sulfide minerals, which is by 5.7% larger compared to the yield obtained by the experimental microbial community.