[Effect of temperature on the rate of oxidation of pyrrhotite-rich sulfide ore flotation concentrate and the structure of the acidophilic chemolithoautotrophic microbial community]

Oxidation of flotation concentrate of a pyrrhotite-rich sulfide ore by acidophilic chemolithoautotrophic microbial communities at 35, 40, and 45 degrees C was investigated. According to the physicochemical parameters of the liquid phase of the pulp, as well as the results of analysis of the solid residue after biooxidation and cyanidation, the community developed at 40 degrees C exhibited the highest rate of oxidation. The degree of gold recovery at 35, 40, and 45 degrees C was 89.34, 94.59, and 83.25%, respectively. At 40 degrees C, the highest number of microbial cells (6.01 x 10(9) cells/mL) was observed. While temperature had very little effect on the species composition of microbial communities, except for the absence of Leptospirillum ferriphilum at 35 degrees C, the shares of individual species in the communities varied with temperature. Relatively high numbers of Sulfobacillus thermosulfidooxidans, the organism oxidizing iron and elemental sulfur at higher rates than other acidophilic chemolithotrophic species, were observed at 40 degrees C.

[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.

[Leaching of copper ore of the Udokanskoe deposit at low temperatures by an association of acidophilic chemolithotrophic microorganisms]

Pure cultures of indigenous microorganisms Acidithiobacillus ferrooxidans strain TFUd, Leptospirillum ferrooxidans strain LUd, and Sulfobacillus thermotolerans strain SUd have been isolated from the oxidation zone of sulfide copper ore of the Udokanskoe deposit. Regimes of bacterial-chemical leaching of ore have been studied over a temperature range from -10 to +20 degrees C. Effects of pH, temperature, and the presence of microorganisms on the extraction of copper have been shown. Bacterial leaching has been detected only at positive values of temperature, and has been much more active at +20 than at +4 degrees C. The process of leaching was more active when the ore contained more hydrophilic and oxidized minerals. The possibility of copper ore leaching of the Udokanskoe deposit using sulfuric acid with pH 0.4 at negative values of temperature and applying acidophilic chemolithotrophic microorganisms at positive values of temperature and low pH values was shown.

[Species and strain composition of microbial associations oxidizing different types of gold-bearing concentrates]

Quantitative abundance of microbial species within an association was found to depend on the energy substrate and the oxidation temperature of sulfide minerals. The number of microbial cells varied depending on the position of reactor in the chain, i.e., the stage of the energy substrate oxidation. Microbial associations oxidized the energy substrate more efficiently than any of their individual components. The increase in pulp density up to the solid : liquid ratio of 1 : 2.5 had an unfavorable effect on microorganisms comprising microbial associations.

[Oxidation of sulfur-containing substrates by an association of acidophilic chemolithotrophic microorganisms]

Quantitative and qualitative changes in the content of elements in the solid and liquid phases occurred as the pulp moved through fermenters during biooxidation of an ore flotation concentrate. The association of microorganisms were adapted for utilizing sulfur-containing substrates; however, the rate of their oxidation was insufficient, which led to an increase in the amount of sodium cyanide required for gold recovery. The replacement of one-fourth of the liquid phase of the pulp (density, 13%) with a mineral medium without an energy source, the fractional addition of FeSO4 x 7H2O (1 g/l per day), and the improvement of pulp aeration made it possible to increase the content of SO4(2-) by 80.7, 86.2, and 58.5%, respectively. When one-fourth of the liquid phasa of the pulp (density, 24%) was replaced with a mineral medium without an energy source, the rate of additional oxidation of sulfide minerals increased, which increased the efficiency of gold extraction into solution and gold recovery on charcoal by 3.4 and 3.6%, respectively, and reduced sodium cyanide consumption by 3 kg/ton.

[Effect of acidic treatment of the chemical composition and bacterial oxidation of arsenic-bearing gold concentrate]

Effect of acidic pretreatment of arsenic-bearing gold concentrate, a promising gold source, on its chemical composition and efficiency of its bacterial oxidation (BO) was studied. The titer of sulfobacilli during BO of the concentrate after high-temperature acidic treatment was 9.0 x 10(7) cells/ml, the degree of arsenic sulfide oxidation being 71.1%, and in the control, 6.5 x 10(7) cells/ml with the oxidation degree as low as 48.7%. Deeper oxidation of the main gold-containing mineral, arsenic sulfide, would allow more efficient gold recovery from the concentrate.

[Sulfobacillus sibiricus sp. nov., a new moderately thermophilic bacterium]

In the course of pilot industrial testing of a biohydrometallurgical technology for processing goldarsenic concentrate obtained from the Nezhdaninskoe ore deposit (East Siberia, Sakha, Yakutiya), a new gram-positive rod-shaped spore-forming moderately thermophilic bacterium (designated as strain N1) oxidizing Fe2+, S0, and sulfide minerals in the presence of yeast extract (0.02%) was isolated from a dense pulp. Physiologically, strain N1 differs from previously described species of the genus Sulfobacillus in having a somewhat higher optimal growth temperature (55 degrees C). Unlike the type strain of S. thermosulfidooxidans, strain N1 could grow on medium with 1 mM thiosulfate or sodium tetrathionate as a source of energy only within several passages and failed to grow, in the absence of an inorganic energy source, on media with sucrose, fructose, glucose, reduced glutathione, alanine, cysteine, sorbitol, sodium acetate, or pyruvate. The G + C content of the DNA of strain N1 was 48.2 mol %. The strain showed 42% homology after DNA-DNA hybridization with the type strain of S. thermosulfidooxidans and 10% homology with the type strain of S. acidophilus. The isolate differed from previously studied strains of S. thermosulfidooxidans in the structure of its chromosomal DNA (determined by the method of pulsed-field gel electrophoresis) which remained stable as growth conditions were changed. According to the results of the 16S rRNA gene analysis, the new strain forms a single cluster with the bacteria of the species Sulfobacillus thermosulfidooxidans (sequence similarity of 97.9-98.6%). Based on these genetic and physiological features, strain N1 is described as a new species Sulfobacillus sibiricus sp. nov.

[Phenotypic features of Ferroplasma acidiphilum strains Yt and Y-2]

Earlier, we described a new family of mesophilic, strictly autotrophic Fe(2+)-oxidizing archaebacteria, Ferroplasmaceae, which belongs to the order Thermoplasmales and includes the genus Ferroplasma and species F. acidiphilum (strain YT) [1]. The present work is concerned with a comparative study of phenotypic characteristics of the type strain YT and a new strain, F. acidiphilum Y-2, isolated from dense pulps produced during oxidation of arsenogold concentrates from the Bakyrchikskoe (Kazakhstan) and Olimpiadinskoe (Krasnoyarsk Krai) ore deposits, respectively. The G + C content of DNA from strains YT and Y-2 comprised 35.1 and 35.2 mol%, respectively; the level of DNA-DNA homology between the strains was 84%. Restriction profiles of chromosomal DNA from both strains exhibited a similarity coefficient of 0.87. Genotypic characteristics of these strains indicate their affiliation to the same species. The cells of both strains are polymorphic and lack cell walls. Strains of F. acidiphilum oxidized ferrous oxide and pyrite as the sole source of energy and fixed carbon dioxide as the sole carbon source. Strains required yeast extract as a growth factor. Optimum pH for cell growth ranged from 1.7 to 1.8; the temperature optima for the growth of strains YT and Y-2 were 34-36 and 40-42 degrees C, respectively. Comparative analysis of total lipids revealed their close similarity in the strains; two glycophospholipids comprised 90% of total lipids: lipid I, beta-D-glucopyranosylcaldarchaetidylglycerol (about 55%), and lipid II, trihexosylcaldarchaetidylglycerol (26%), whose isopranyl chains contained no cyclopentane rings. The carbohydrate fraction of lipid I hydrolysate contained only D-glucose, whereas hydrolysate of lipid II contained both D-glucose and D-galactose in a molar ratio of 2:1. Thus, it was established that the intraspecific phylogenetic divergence within F. acidiphilum is manifested in two the strains by different temperature optima against the background of similarity in other phenotypic properties.

[Characteristics of the restriction profile of chromosomal DNA in strains of Acidithiobacillus ferroxidans, adapted to various oxidation substrates]

Restriction profiles of chromosomal DNA were studied in different Acidithiobacillus ferrooxidans strains grown on medium with Fe2+ and further adapted to another oxidation substrate (S0, FeS2, or sulfide ore concentrates). The restriction endonuclease XbaI digested the chromosomal DNA from different strains into different numbers of fragments of various sizes. Adaptation of two strains (TFBk and TFN-d) to new oxidation substrates resulted in structural changes in XbaI-restriction patterns of their chromosomal DNA. Such changes in the DNA restriction patterns occurred in strain TFBk after the adaptation to precyanidated gravitational pyrite-arsenopyrite concentrate (no. 1) from the Nezhdaninskoe deposit or to copper-containing ore from the Udokanskoe deposit and also in strain TFN-d adapted to untreated pyrite-arsenopyrite concentrate (no. 2) from the Nezhdaninskoe deposit. No changes in the number or size of the XbaI-restriction patterns of chromosomal DNA were revealed in either strain TFBk cultivated on media with pyrite from the Angren and Tulun deposits or in strains TFN-d and TFO grown on media with S0 and pyrite. Neither were changes observed in the XbaI-restriction patterns of the DNA from strain TFV-1, isolated from the copper ore of the Volkovskoe deposit, when Fe2+ was substituted with alternative substrates--S0, pyrite or concentrate no. 2 from the ore of Nezhdaninskoe deposit. In strain TFO, no differences in the XbaI-restriction patterns of the chromosomal DNA were revealed between the culture grown on medium containing concentrate no. 2 or the concentrate of surface-lying ore from Olimpiadinskoe deposit and the culture grown on medium with Fe2+. When strain TFO was cultivated on the ore concentrate from deeper horizons of the Olimpiadinskoe deposit, which are characterized by lower oxidation degree and high antimony content, mutant TFO-2 differing from the parent strain in the chromosomal DNA structure was isolated. The correlation between the lability of chromosomal DNA structure in A. ferrooxidans strains and the physical and chemical peculiarities of the isolation substrate and habitat is discussed.

[Strain polymorphism of the plasmid profiles in Acidithiobacillus ferrooxidans]

Plasmid profiles were studied in 27 Acidithiobacillus ferrooxidans strains isolated from different geographic zones and substrates differing in the composition of the main sulfide minerals, and also in experimentally obtained strains with acquired enhanced resistance to the ions of heavy metals (Fe, Ni, Cu, Zn, As). In 16 out of 20 strains isolated from different substrates, one to four 2- to 20-kb and larger plasmids were revealed. Plasmids were found in all five strains isolated from gold-containing pyrite-arsenopyrite ores and concentrates, in nine of 11 strains isolated from the ores and concentrates containing nonferrous metals, and in two of four strains isolated from the oxidation substrates of simple composition (mine waters, pyritized coals, active sludge). Changes in the plasmid profiles in some A. ferrooxidans strains (TFZ, TFI-Fe, TFV-1-Cu) with experimentally enhanced resistance to Zn2+, Fe3+, and Cu2+, respectively, were noted as compared with the initial strains. After 30 passages on S0-containing medium, strain TFBk showed changes in the copy number of plasmids. The role of plasmids in the processes of oxidation of energy substrates and in the acquired enhanced resistance to the heavy metal ions is discussed.

Ferroplasma acidiphilum gen. nov., sp. nov., an acidophilic, autotrophic, ferrous-iron-oxidizing, cell-wall-lacking, mesophilic member of the Ferroplasmaceae fam. nov., comprising a distinct lineage of the Archaea

An isolate of an acidophilic archaeon, strain YT, was obtained from a bioleaching pilot plant. The organism oxidizes ferrous iron as the sole energy source and fixes inorganic carbon as the sole carbon source. The optimal pH for growth is 1.7, although growth is observed in the range pH 1.3 to 2.2. The cells are pleomorphic and without a cell wall. 16S rRNA gene sequence analysis showed this strain to cluster phylogenetically within the order 'Thermoplasmales' sensu Woese, although with only 89.9 and 87.2% sequence identity, respectively, to its closest relatives, Picrophilus oshimae and Thermoplasma acidophilum. Other principal differences from described species of the 'Thermoplasmales' are autotrophy (strain YT is obligately autotrophic), the absence of lipid components typical of the ' Thermoplasmales' (no detectable tetraethers) and a lower temperature range for growth (growth of strain YT occurs between 15 and 45 degrees C). None of the sugars, amino acids, organic acids or other organic compounds tested was utilized as a carbon source. On the basis of the information described above, the name Ferroplasma acidiphilum gen. nov., sp. nov. is proposed for strain YT within a new family, the Ferroplasmaceae fam. nov. Strain YT is the type and only strain of F. acidiphilum. This is the first report of an autotrophic, ferrous-iron-oxidizing, cell-wall-lacking archaeon.

[Sulfurococcus yellowstonii sp. nov/--a new species of iron- and sulfur-oxidizing thermoacidophilic Archaeobacterium]

A spheric thermoacidophilic sulphur-oxidizing archaebacterium (strain Str6kar) has been isolated from the hydrotherm of the Yellowstone National Park (USA). The isolate is a facultative autotroph. The strain Str6kar oxidizes elemental sulfur, ferrous sulfate and sulphide minerals, it is capable of using some organic compounds. The isolate grows at the temperature of 40-80 degrees. The content of GC-pairs in the DNA of the bacterium is 44.6 mol%. The level of homology of the isolates DNA for the Str6kar and Sulfurococcus mirabilis is 12-15%, for Str6kar and Metallosphaera sedula-0.7-7%. According to the structure of the 5s rRNA, the described bacteria are similar to S. mirabilis. Basing on morphological, physiological and molecular-genetical features, this archaeobacterium can be presented as a new species of the genus of Sulfurococcus-S. yellowstonii sp. nov.

[Role of phospholipids in the fractionation of stable sulfur isotopes during oxidation by Thiobacillus ferrooxidans]

The action of Thiobacillus ferrooxidans on elementary suhur was shown to be a step-wise process connected with the formation of its colloidal forms having a different isotope composition. Certain sulfur forms are in complex with phospholipids. Both exogenous and endogenous phospholipids are involved in the dissolving of sulfur and in the fractionation of its isotopes. Exogenous phospholipids are more active. The authors discuss the role of phospholipids in the solution of sulfur and in its transport into the cell in the course of oxidation by T. ferrooxidans.

[Fractionation of stable isotopes of sulfur during its oxidation by Thiobacillus ferrooxidans]

The fractionation of sulfur isotopes was studied in the process of sulfur oxidation by Thiobacillus ferrooxidans. The isotope effect was observed at all stages of the bacterial growth during sulfur oxidation; as a result, residual sulfur became heavier whereas the fraction of colloidal sulfur and the fraction of sulfates became lighter. The isotope differences between the residual sulfur and the sulfates were greatest at the end of the lag phase (delta 34S = 0.38%) and the beginning of the stationary phase of the cultural growth (delta 34S = 0.34%). As was shown in model experiments, the phospholipids lecithin and cephalin can dissolve sulfur and form products enriched in 32S(delta 34S = -0.51 -1.60%). The mechanism of oxidation of elementary sulfur by Thiobacillus ferrooxidans is discussed.

[Morphogenesis and the fine structure of Stibiobacter senarmontii]

The morphogenesis and fine structure of Stibiobacter senarmontii were studied during its cultivation in the autotrophic conditions of growth in a mineral medium as well as in a medium containing yeast extract. The morphology of the organism was shown to be variable. A young culture was represented mainly by rods with three flagella. Coccoid, club-shaped and branching forms were observed during aging of the culture. The cells multiplied by irregular division and by breaking along the partition of the parent cell. The latter process yielded cell aggregates looking like rings and hieroglyphs. Electronograms revealed a complex membrane apparatus, polyribosomes, large electron-transparent inclusions, and unknown electron-dense inclusions in the nuclear zone. The cell wall looked on cross-sections as a three-layer structure. The assignment of St. senarmontii to Gram-positive bacteria is discussed. The morphogenesis of this organism suggests that it is related to the coryneform group of bacteria.

[Submicroscopic organization and spore formation of Desulfotomaculum nigrificans]

The submicroscopic organization and spore formation were studied in two strains of Desulfotomaculum nigrificans, 435 and 781. Cross-sections of cells fixed with osmic acid and contrasted with uranyl acetate and lead citrate revealed a cell wall devoid of the outer lipoprotein membrane, which was typical of gram-positive bacteria. The cell wall consisted of three electron-dense layers and two layers of lower electron density. A layer of a microcapsule having fibrillar structure and a thickness of 23-33 nm was detected on the surface of the cell wall. The cytoplasmic membrane and intracellular membrane structures were represented by the Robertson membrane about 9 nm thick. The cytoplasm contained electron-dense polyribosomal granules and inclusions having fine-granular structure. The nucleoid was located in the central part of the cell as an electron-transparent zone penetrated with electron-dense DNA threads 2.5 nm thick. The paper presents microphotographs of the main stages of spore formation which follows the mechanism described for bacteria of the Bacillus genus. The poles of spindle-like cells have electron-dense disk-shaped formations covered with a three-layer membrane and containing electron-dense granules, apparently, corresponding to polyribosomes.

[Speroplast behavior in cultures of Thermus ruber]

Spheroplasts spontaneously originating in cultures of Thermus ruber, which are cultivated on potato-peptone media, are capable of growth and multiplication. They may reach 10 mc in diameter. Spheroplasts multiply by budding which can be preceded with inner division or budding; as a result 2--9 and more protoplast bodies are formed under the "envelope" of a spheroplast. Self-reproduction of spheroplasts is most active in a semiliquid potato-meat-peptone medium containing 0.2--0.3 per cent of agar. Microcolonies, which are clusters of spheroplasts in the process of budding, are formed at 45 degrees C in this medium during 1--2 days. Reversion of spheroplasts to rod-like cells occurs if L-lysine and/or DL-alpha-aline are added to the potato-peptone medium. Spheroplasts spontaneously produced by Thermus ruber are similar to the unstable type of L-form in their fine organization and behaviour in cultures.

[Coccoid cells and spheroplasts in cultures of the genus Thermus]

The formation of capable of self-reproduction coccoid cells, and of spheroplasts, was studied in the cultures of Thermus ruber and pigmentless Thermus sp. by light and electron microscopy. The primary origination of cocci might be due to non-uniform or multiple cell division. Spheroplasts can be produced either from coccoid or from rod-like cells as a result of autolysis of the glycopeptide layer of the cell wall. The spheroplasts of the cultures belonging to the Thermus genus are characterized by osmotic stability and a peculiar appearance due to a strongly developed periplasmic space and the eccentric arrangement of the protoplast in it.

[Fine structure of Chloroflexus aurantiacus var. mesophilus (nom. prof.) grown in the light under aerobic and anaerobic conditions]

The fine structure was studied in two mesophilic strains of Chloroflexus aurantiacus var. mesophilus (nom. prof.): KN-4 and BR-1. Trichomes are covered with a mucous fibrillar sheath which is more developed in the KN-4 strain. Photosynthetic structures, "chlorobium-vesicles", are located at the periphery of the cells of both strains. The structure of the cell was is typical of gram-negative microorganisms. By their electron density and dimensions, inner cytoplasmic structures are identified as poly-beta-hydroxybutyric acid, polyphosphates, and polysaccharides. When the strain BR-I was grown in aerobic conditions in the light, "chlorobium-vesicles" were not synthesized and intracytoplasmic membranes were represented by small tubular-vesicular invaginations. When the cells were grown under anaerobic conditions in the lgiht, numerous "chlorobium-vesicles" were formed, and additional large vesicular membrane systems appeared; these systems occupied over 20 per cent of the cell volume. Possible relationship between the membrane structures and the synthesis of bacteriochlorophyll a and c is discussed.

[Function of surface membrane structures in Thiobacillus thiooxidans]

The function of the surface membrane structures was studied with cytochemical techniques on ultrathin sections of Thiobacillus thiooxidans. The transport of elementary sulphur inside the cell involves the surface membrane structures, while oxidation of the sulphur to sulphuric acid takes place on the outer surface of the cytoplasmic membrane. The surface membrane structures are supposed also to participate in the primary dissolution of elementary sulphur at the site of contact of the cells with the mineral.

[Comparative study of the ultrastructure of vibrioid green sulfur bacteria]

The fine structure of the cells was investigated on the ultrathin sections of green sulphur bacteria, two strains of Chlorobium vibrioforme, two strains of Pelodictyon luteolum, and one strain of Pelodictyon phaeum. All strains possess similar photosynthetic structures --"chlorobium-vesicules" underlying the cytoplasmic membrane. Irregularly localized, gaseous vesicules of the rhombic shape were discerned in the cytoplasm of P. luteolum and P. phaeum. The vesicules were surrounded by a unilayer membrane. The cytoplasmic membrane produced invaginations of the mesosomal type. Elementary sulphur as a product of oxidation of hydrogen sulphide, is presumed to be liberated from the cells by means of sacs, or invaginations, formed by the cytoplasmic membrane. The taxonomy of the vibrioid green sulphur bacteria is discussed.