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Introduction: Alcanivorax , a typical alkane-degrading bacterium, has demonstrated the ability to utilize inorganic electron donor in some reports. However, a comprehensive analysis of its potentiality to utilize inorganic electron donor is still lacking. Methods: In this study, genomic and phylogenetic analyzes were used to explore the potential oxidative capacity of inorganic compounds in Alcanivorax. And its functions were verified through physiological experiments. Results: The sulfur oxidation-related genes sqr and tsdA are prevalent and have various evolutionary origins. Potential genes for CO oxidation were present in 39 strains, whereas genes associated with iron, hydrogen, and ammonia oxidation were either rare or absent. The physiological functions of Sqr and TsdA were confirmed in six representative strains under heterotrophic conditions. Adding thiosulfate enhanced Alcanivorax growth. However, Alcanivorax bacteria perform sulfide detoxification through Sqr rather than by gaining energy via sulfide oxidation Although no strain was confirmed to be chemoautotrophs, we discovered that the two clades, A. xenomutans and A. profundimaris , can grow under conditions with very low organic matter. Discussion: The ability to utilize inorganic compounds as a supplementary energy source and adapt to carbon oligotrophic growth may contribute to the prevalence of Alcanivorax in marine ecosystems. [ABSTRACT FROM AUTHOR]

IntroductionAlcanivorax, a typical alkane-degrading bacterium, has demonstrated the ability to utilize inorganic electron donor in some reports. However, a comprehensive analysis of its potentiality to utilize inorganic electron donor is still lacking.MethodsIn this study, genomic and phylogenetic analyzes were used to explore the potential oxidative capacity of inorganic compounds in Alcanivorax. And its functions were verified through physiological experiments.ResultsThe sulfur oxidation-related genes sqr and tsdA are prevalent and have various evolutionary origins. Potential genes for CO oxidation were present in 39 strains, whereas genes associated with iron, hydrogen, and ammonia oxidation were either rare or absent. The physiological functions of Sqr and TsdA were confirmed in six representative strains under heterotrophic conditions. Adding thiosulfate enhanced Alcanivorax growth. However, Alcanivorax bacteria perform sulfide detoxification through Sqr rather than by gaining energy via sulfide oxidation Although no strain was confirmed to be chemoautotrophs, we discovered that the two clades, A. xenomutans and A. profundimaris, can grow under conditions with very low organic matter.DiscussionThe ability to utilize inorganic compounds as a supplementary energy source and adapt to carbon oligotrophic growth may contribute to the prevalence of Alcanivorax in marine ecosystems.

With the accelerated modernization of agriculture and industry, sulfides have been released into the environment as a by-products of various production processes. Elevated levels of sulfide pose a threat to organisms' health and disrupt ecosystem equilibrium. This study successfully isolated two highly efficient sulfur-oxidizing strains, namely Pseudomonas aeruginosa GHWS3 and Sphingobacterium sp. GHWS5. Neither strain exhibited hemolytic activity or pathogenicity. Additionally, GHWS3 inhibited the common aquaculture pathogen Vibrio anguillarum, while GHWS5 exhibited inhibitory effects against Vibrio harveyi. GHWS3 and GHWS5 demonstrated effective removal of sulfide under the following conditions: temperature range of 20–40 °C, pH level of 4.5–8.5, salinity range of 0–50‰, C/N ratio of 5–15, and sulfide concentration of 20–200 mg/L. By amplifying the key functional genes of the sulfur-oxidizing Sox and rDsr systems in both GHWS3 and GHWS5 strains, potential desulfurization pathways were analyzed. Furthermore, both strains displayed high efficiency in removing sulfides from actual aquaculture pond substrate mixtures. The findings of this study provide two promising candidate strains for sulfides removal from farm tailwater, industrial wastewater, and domestic wastewater. [ABSTRACT FROM AUTHOR]

The recent expansion of studies at hydrothermal submarine vents from investigation of abiotic methane formation to include abiotic production of organics such acetate and formate, and rising interest in processes of abiotic organic synthesis on the ocean-world moons of Saturn and Jupiter, have raised interest in potential Earth analogs for investigation of prebiotic/abiotic processes to an unprecedented level. The deep continental subsurface provides an attractive target to identify analog environments where the influence of abiotic carbon cycling may be investigated, particularly in hydrogeological isolated fracture fluids where the products of chemical water-rock reactions have been less overprinted by the biogeochemical signatures of the planet's surficial water and carbon cycles. Here we report, for the first time, a comprehensive set of concentration measurements and isotopic signatures for acetate and formate, as well as the dissolved inorganic and organic carbon pools, for saline fracture waters naturally flowing 2.4 km below surface in 2.7 billion year-old rocks on the Canadian Shield. These geologically ancient fluids at the Kidd Creek Observatory were the focus of previous investigations of fracture fluid geochemistry, microbiology and noble gas-derived residence times. Here we show the fracture waters of Kidd Creek contain high concentrations of both acetate and formate with concentrations from 1200 to 1900 µmol/L, and 480 to 1000 µmol/L, respectively. Acetate and formate alone account for more than 50–90% of the total DOC – providing a very simple "organic soup". The unusually elevated concentrations and profoundly 13C-enriched nature of the acetate and formate suggest an important role for abiotic organic synthesis in the deep carbon cycle at this hydrogeologically isolated site. A variety of potential abiotic production reactions are discussed, including a radiolytically driven H, S and C deep cycle that could provide a mechanism for sustaining deep subsurface habitability. Scientific discoveries are beginning to reveal that organic-producing reactions that would have prevailed on Earth before the rise of life, and that may persist today on planets and moons such as Enceladus, Europa and Titan, can be accessed in some specialized geologic settings on Earth that provide valuable natural analog environments for the investigation of abiotic organic chemistry outside the laboratory. [ABSTRACT FROM AUTHOR]

A chemolithotrophic bacterium was isolated from sulfur hot spring. According to phenotypic traits and 16-23S rDNA intergenic spacer region analysis, the isolate was identified and named as Acidithiobacillus sp. MR39, which was a gram-negative, rod- shape and nonmotile bacterium. The strain was able to grow in a synthetic liquid medium supplemented with the mineral ore as the source of energy. The optimum conditions were found to be within initial pH range of 2.0-2.5, at 34±1°C and with shaking at 120 rpm. The bacterium had a remarkable potential for mineralization of 88% iron, 75% copper, 59% zinc, 59% nickel and 40% cobalt upon their growth in the liquid media. After adapting the bacterial cells to copper ions in 100 mM for 5-day incubation, biorecovery of Cu increased about 10% comparing to unadapted cells that are able to dissolve approximately 15% of total cu of mineral concentrate. Considering the finding in this study, the strain MR39 offers a great prospect for in situ extraction of metals from various ores along with other indigenous bacteria that can grow under ambient conditions. [ABSTRACT FROM AUTHOR]

Pyrite (FeS2) is the most abundant sulfide mineral on Earth and represents a significant reservoir of reduced iron and sulfur both today and in the geologic past. In modern environments, oxidative transformations of pyrite and other metal sulfides play a key role in terrestrial element partitioning with broad impacts to contaminant mobility and the formation of acid mine drainage systems. Although the role of aerobic micro-organisms in pyrite oxidation under acidic- pH conditions is well known, to date there is very little known about the capacity for aerobic micro-organisms to oxidize pyrite at circumneutral pH. Here, we describe two enrichment cultures, obtained from pyrite-bearing subsurface sediments, that were capable of sustained cell growth linked to pyrite oxidation and sulfate generation at neutral pH. The cultures were dominated by two Rhizobiales species ( Bradyrhizobium sp. and Mesorhizobium sp.) and a Ralstonia species. Shotgun metagenomic sequencing and genome reconstruction indicated the presence of Fe and S oxidation pathways in these organisms, and the presence of a complete Calvin-Benson-Bassham CO2 fixation system in the Bradyrhizobium sp. Oxidation of pyrite resulted in thin (30-50 nm) coatings of amorphous Fe( III) oxide on the pyrite surface, with no other secondary Fe or S phases detected by electron microscopy or X-ray absorption spectroscopy. Rates of microbial pyrite oxidation were approximately one order of magnitude higher than abiotic rates. These results demonstrate the ability of aerobic microbial activity to accelerate pyrite oxidation and expand the potential contribution of micro-organisms to continental sulfide mineral weathering around the time of the Great Oxidation Event to include neutral- pH environments. In addition, our findings have direct implications for the geochemistry of modern sedimentary environments, including stimulation of the early stages of acid mine drainage formation and mobilization of pyrite-associated metals. [ABSTRACT FROM AUTHOR]

Biomining is defined as biotechnology for metal recovery from minerals, and is promoted by the concerted effort of a consortium of acidophile prokaryotes, comprised of members of the Bacteria and Archaea domains. Ferroplasma acidiphilum and Leptospirillum ferriphilum are the dominant species in extremely acid environments and have great use in bioleaching applications; however, the role of each species in this consortia is still a subject of research. The hypothesis of this work is that F. acidiphilum uses the organic matter secreted by L. ferriphilum for growth, maintaining low levels of organic compounds in the culture medium, preventing their toxic effects on L. ferriphilum. To test this hypothesis, a characterization of Ferroplasma acidiphilum strain BRL-115 was made with the objective of determining its optimal growth conditions. Subsequently, under the optimal conditions, L. ferriphilum and F. acidiphilum were tested growing in each other's supernatant, in order to define if there was exchange of metabolites between the species. With these results, a mixed culture in batch cyclic operation was performed to obtain main specific growth rates, which were used to evaluate a mixed metabolic model previously developed by our group. It was observed that F. acidiphilum, strain BRL-115 is a chemomixotrophic organism, and its growth is maximized with yeast extract at a concentration of 0.04% wt/vol. From the experiments of L. ferriphilum growing on F. acidiphilum supernatant and vice versa, it was observed that in both cases cell growth is favorably affected by the presence of the filtered medium of the other microorganism, proving a synergistic interaction between these species. Specific growth rates were obtained in cyclic batch operation of the mixed culture and were used as input data for a Flux Balance Analysis of the mixed metabolic model, obtaining a reasonable behavior of the metabolic fluxes and the system as a whole, therefore consolidating the model previously developed. © 2016 American Institute of Chemical Engineers Biotechnol. Prog., 32:1390-1396, 2016 [ABSTRACT FROM AUTHOR]

The impact of temperature (0-80°C) on anaerobic biogeochemical processes and prokaryotic communities in marine sediments (tidal flat) was investigated in slurries for up to 100 days. Temperature had a non-linear effect on biogeochemistry and prokaryotes with rapid changes over small temperature intervals. Some activities (e.g. methanogenesis) had multiple 'windows' within a large temperature range (∼10 to 80°C). Others, including acetate oxidation, had maximum activities within a temperature zone, which varied with electron acceptor [metal oxide (up to ∼34°C) and sulphate (up to ∼50°C)]. Substrates for sulphate reduction changed from predominantly acetate below, and H2 above, a 43°C critical temperature, along with changes in activation energies and types of sulphate-reducing Bacteria. Above ∼43°C, methylamine metabolism ceased with changes in methanogen types and increased acetate concentrations (>1 mM). Abundances of uncultured Archaea, characteristic of deep marine sediments (e.g. MBGD Euryarchaeota, 'Bathyarchaeota') changed, indicating their possible metabolic activity and temperature range. Bacterial cell numbers were consistently higher than archaeal cells and both decreased above ∼15°C. Substrate addition stimulated activities, widened some activity temperature ranges (methanogenesis) and increased bacterial (×10) more than archaeal cell numbers. Hence, additional organic matter input from climate-related eutrophication may amplify the impact of temperature increases on sedimentary biogeochemistry. [ABSTRACT FROM AUTHOR]

A total of 75 microorganisms were obtained from high-sulfur content environmental samples using different sulfur sources. Fifty-four of them had the ability to oxidize sulfur at 1% (w/v) in liquid culture, however only three of them AZCT-M125-5, AZCT--M125-6, and AZCT-M 125-7 were able to grow autotrophycally using elemental sulfur at concentrations higher than 1 % and up to 9 % (w/v) as energy source. They produce more than 300 mg sulfate/L. Also, these microbial cultures were able to produce sulfate within pH 3 to 7. Analysis based on 16S rRNA gene sequences indicated that microbial cultures AZCT-M125-5 and AZCT-M125-6 were closely related to Acidithiobacillus thiooxidans while identification of AZCT-M 125-7 was not possible. According to the results, these three microorganisms can be excellent candidates for the future development of alternative biotechnological processes for the treatment of hazardous wastes containing sulfur. [ABSTRACT FROM AUTHOR]

Microbial fuel cells (MFCs) have applications other than electricity production, including the capacity to power desirable reactions in the cathode chamber. However, current knowledge of the microbial ecology and physiology of biocathodes is minimal, and as a result more research dedicated to understanding the microbial communities active in cathode biofilms is required. Here we characterize the microbiology of denitrifying bacterial communities stimulated by reducing equivalents generated from the anodic oxidation of acetate. We analyzed biofilms isolated from two types of cathodic denitrification systems: (1) a loop format where the effluent from the carbon oxidation step in the anode is subjected to a nitrifying reactor which is fed to the cathode chamber and (2) an alternative non-loop format where anodic and cathodic feed streams are separated. The results of our study indicate the superior performance of the loop reactor in terms of enhanced current production and nitrate removal rates. We hypothesized that phylogenetic or structural features of the microbial communities could explain the increased performance of the loop reactor. We used PhyloChip with 16S rRNA (cDNA) and fluorescent in situ hybridization to characterize the active bacterial communities. Our study results reveal a greater richness, as well as an increased phylogenetic diversity, active in denitrifying biofilms than was previously identified in cathodic systems. Specifically, we identified Proteobacteria, Firmicutes and Chloroflexi members that were dominant in denitrifying cathodes. In addition, our study results indicate that it is the structural component, in terms of bacterial richness and evenness, rather than the phylogenetic affiliation of dominant bacteria, that best corresponds to cathode performance. [ABSTRACT FROM AUTHOR]

Abstract: Nickel is an important metal in human life and in the industry. In recent years, the world nickel demand has been driven by soaring steel production, particularly in China. With the rapid growing demand for nickel coupled with the depletion of high grade sulphide reserves, low-grade nickel ores, which cannot be economically processed by conventional metallurgical processes, become increasingly important sources of nickel. Laterite ore, which is often considered as a low-grade nickel ore, contains several kinds of metal elements including nickel, cobalt, iron, silicon, aluminium, and chromium; and thus, constitutes an alternative source of nickel. The nickel present in nickel laterites is not usually present as discrete minerals, but as cations substituted within manganese oxides, goethite, and/or clays. Because of this, it is difficult to upgrade the ore by beneficiation. As a result, nickel laterites are traditionally processed using pyrometallurgical and hydrometallurgical methods. In recent years, microbiological leaching has been found to be a promising novel technology for recovering valuable minerals from traditionally difficult-to-process ores. Microbial leaching of low-grade ores offers many advantages over other conventional methods due to its relative simplicity, requiring mild operating conditions, low capital costs, low energy input, relatively unskilled labour requirements, and being environmentally friendly. Because of the importance of microbial leaching, recent advances in microbial assisted leaching of nickel laterites are discussed in this paper with emphasis on fungal (chemoorganotrophic) and chemolithotrophic microorganisms. [Copyright &y& Elsevier]

Abstract: The Thiobacillus denitrificans genome contains two sequences corresponding to ATP sulfurylase (Tbd_0210 and Tbd_0874). Both genes were cloned and expressed protein characterized. The larger protein (Tbd_0210; 544 residues) possesses an N-terminal ATP sulfurylase domain and a C-terminal APS kinase domain and was therefore annotated as a bifunctional enzyme. But, the protein was not bifunctional because it lacked ATP sulfurylase activity. However, the enzyme did possess APS kinase activity and displayed substrate inhibition by APS. Truncated protein missing the N-terminal domain had <2% APS kinase activity suggesting the function of the inactive sulfurylase domain is to promote the oligomerization of the APS kinase domains. The smaller gene product (Tbd_0874; 402 residues) possessed strong ATP sulfurylase activity with kinetic properties that appear to be kinetically optimized for the direction of APS utilization and ATP+sulfate production, which is consistent with an enzyme that functions physiologically to produce inorganic sulfate. [Copyright &y& Elsevier]

To explore the bacteria involved in the oxidation of arsenite (As(III)) under denitrifying conditions, three enrichment cultures (ECs) and one mixed culture (MC) were characterized that originated from anaerobic environmental samples. The oxidation of As(III) (0.5 mM) was dependent on NO3− addition and N2 formation was dependent on As(III) addition. The ratio of N2–N formed to As(III) fed approximated the expected stoichiometry of 2.5. A 16S rRNA gene clone library analysis revealed three predominant phylotypes. The first, related to the genus Azoarcus from the division Betaproteobacteria, was found in the three ECs. The other two predominant phylotypes were closely related to the genera Acidovorax and Diaphorobacter within the Comamonadaceae family of Betaproteobacteria, and one of these was present in all of the cultures examined. FISH confirmed that Azoarcus accounted for a large fraction of bacteria present in the ECs. The Azoarcus clones had 96% sequence homology with Azoarcus sp. strain DAO1, an isolate previously reported to oxidize As(III) with nitrate. FISH analysis also confirmed that Comamonadaceae were present in all cultures. Pure cultures of Azoarcus and Diaphorobacter were isolated and shown to be responsible for nitrate-dependent As(III) oxidation. These results, taken as a whole, suggest that bacteria within the genus Azoarcus and the family Comamonadaceae are involved in the observed anoxic oxidation of As(III). [ABSTRACT FROM AUTHOR]

Abstract: In this study, denitrification linked to the oxidation of arsenite (As(III)) to arsenate (As(V)) was shown to be a widespread microbial activity in anaerobic sludge and sediment samples that were not previously exposed to arsenic contamination. When incubated with 0.5mM As(III) and 10mM NO3 −, the anoxic oxidation of As(III) commenced within a few days, achieving specific activities of up to 1.24mmol As(V) formed g−1 volatile suspended solids d−1 due to growth (doubling times of 0.74–1.4d). The anoxic oxidation of As(III) was partially to completely inhibited by 1.5 and 5mM As(III), respectively. Inhibition was minimized by adding As(III) adsorbed onto activated aluminum (AA). The oxidation of As(III) was shown to be linked to the complete denitrification of NO3 − to N2 by demonstrating a significantly enhanced production of N2 beyond the background endogenous production as a result of adding As(III)–AA to the cultures. The N2 production corresponded closely the expected stoichiometry of the reaction, 2.5mol As(III) mol−1 N2–N. The oxidation of As(III) linked to the use of common-occurring nitrate as an electron acceptor may be an important missing link in the biogeochemical cycling of arsenic. [Copyright &y& Elsevier]

Abstract: Industrial microdevices are mostly manufactured by micromachining technology. Materials can be micromachined by various means, including mechanical, optical and chemical. The concerns of environmental impact and production costs are the inspirations behind one alternative method of micromachining, the use of bioleaching. The evaluation of a potential microorganism for the bioleaching machining technology is conducted in the current study. The dissolution of metals by the chemolithotrophic bacteria Acidithiobacillus thiooxidans and Acidithiobacillus ferrooxidans is based on the physical contact between the bacteria and their extracellular secreted metabolites and metals. Cell growth quality during the machining process is also an important issue. The specific metal removal rate is a key criterion to characterize any industrial machining process, defined here by the mass removed in milligrams from 1cm2 of machined area in 1h by a solution with a cellular concentration of 1×108 cells/ml. The authors find that the specific metal removal rates for copper, aluminum and nickel are 0.5mg/h, 0.06mg/h and 0.93mg/h, respectively. [Copyright &y& Elsevier]

The influence of growth rate, the presence of acetate and variation in the dissolved oxygen concentration on the kinetics of nitrite oxidation was studied in suspensions of intact cells of Nitrobacter winogradskyi and Nitrobacter hamburgensis. The cells were grown in nitrite-limited chemostats at different dilution rates under chemolithotrophic and mixotrophic conditions. Growth of N. hamburgensis in continuous culture was dependent on the presence of acetate. Acetate hardly affected the maximal nitrite oxidation rate per cell ( V), but displayed a distinctly negative effect on the saturation constants for nitrite oxidation ( K) of both Nitrobacter species. This effect was reversible; when acetate was removed from the suspensions the K-values for nitrite oxidation returned to their original values. A reduction of the dissolved oxygen concentration from 100% to 18% air saturation slightly decreased the V of chemolithotrophically grown N. winogradskyi cells, whereas a 2.3 fold increase was observed with mixotrophically grown cells of N. hamburgensis. It is suggested that the large variation in K encountered in field samples could be due to this observed phenotypic variability. The V per cell is not a constant, but apparently is dependent on growth rate and environmental conditions. This implies that potential nitrite oxidation activity and numbers of cells are not necessarily related. Considering their kinetic characteristics, it is unlikely that N. hamburgensis is able to compete succesfully with N. winogradskyi for limiting amounts of nitrite under mixotrophic conditions. However, at reduced partial oxygen tensions, N. hamburgensis may become the better competitor. [ABSTRACT FROM AUTHOR]

From an uranium mine three strains of rodshaped, mesophilic, chemolithoautotrophic bacteria were isolated. They grow by oxidation of HS, galena (PbS) and H. Anglesite (PbSO) is formed from galena. No ferrous iron is oxidized by the isolates. They grow between pH 4 and 6.5 at temperatures of about 9 to 41°C (optimum around 27°C). The G+C content of the DNA is around 66 mol %. Based on their ability to oxidize sulfur compounds, the new organisms belong to the genus Thiobacillus. No significant homology with Thiobacillus ferrooxidans and Thiobacillus cuprinus was detected by DNA-DNA hybridization. Therefore the new isolates represent a new species within the genus Thiobacillus. Based on the unusual growth on galena, we name the new species Thiobacillus plumbophilus (type strain Gro 7; DSM 6690). [ABSTRACT FROM AUTHOR]

From the shallow geothermally heated seafloor at the beach of Porto di Levante (Vulcano, Italy) 8 strains of long, tiny rods were isolated, which represent the first marine metal-mobilizing bacteria. Cells are Gram negative. They grow in a temperature range between 23 and 41°C with an optimum around 37°C at a salt concentration of up to 6.0% NaCl. The isolates are obligately chemolithotrophic, acidophilic aerobes which use sulfidic ores, elemental sulfur or ferrous iron as energy sources and procedure sulfuric acid. They show an upper pH-limit of growth at around 4.5. The G+C content of their DNA is around 64 mol%. Based on the results of the DNA-DNA hybridization they represent a new group within the genus Thiobacillus. Isolate LM3 is described as the type strain of the new species Thiobacillus prosperus. [ABSTRACT FROM AUTHOR]

A new chemolithotrophic nitrite-oxidizing bacterium, for which the name Nitrospira marina is proposed, was isolated from the Gulf of Maine. N. marina is a Gramnegative curved rod which may form spirals with 1 to 12 turns. Cells have a unique periplasmic space and lack intracytoplasmic membranes and carboxysomes. N. marina is an obligate chemolithotroph, but best growth is obtained in a mixotrophic medium. N. marina may be one of the most prevalent nitrite-oxidizing bacteria in some oceanic environments. Type strain is field with American Type Culture Collection (ATCC 43039). [ABSTRACT FROM AUTHOR]

In this work is evaluated the bioleaching capacity of a bacterium isolated from a mine in Guanajuato, México, namely LR-1. The bacterium oxidized Fe2+ and S 2 O 3 2− at acidic pH for its energy metabolism. This oxidant activity provided Fe3+ and/or protons that provoke sulfide ore dissolution. Five sulfide ore samples were obtained from different Mexican mines: Remedios, Guerrero, Bolañitos, Aldama, and Ocampo. The Ag, Cr, Cu, Fe, Pb, and Zn contents in the ores was analyzed by atomic absorption. Other physicochemical properties, including pH, electrical conductivity, and oxide-reducing potential, were also measured. Bioleaching was evaluated by metal concentration in the medium due to bacterial growth developed in basal salt medium with 2% (w / v) mineral in acidic conditions at 37 °C. There was an Increase in the percentage release of Ag (18.66% to 29.85%), Cu (60.90% to 73.66%), and Cr (11.71% to 15.04%), with respect to chemical leaching, mainly from the Remedios ore. A phylogenetic analysis of the 16S rRNA gene sequences revealed that bacterium LR-1 belongs to the genus Brevibacillus. There are no known species from this genus related with the leaching processes. This is the first report of an acidophile chemolithoautotrophic iron oxidizing bacterium from the genus Brevibacillus in the metal bioleaching. Therefore, these data contribute to the knowledge of the hydrometallurgical microbiology. • A new chemolithoautotrophic bacterium (LR-1) is proposed for the bioleaching of sulfurbearing minerals. • The percentage of metal bioleaching was higher that chemical leaching. • Phylogenetic analysis related strain LR-1 with species of the genus Brevibacillus. • This report is the first of a strain of the genus Brevibacillus in metal bioleaching. [ABSTRACT FROM AUTHOR]