Acidophilic Chemolithotrophic Bacteria Research Articles

Biocorrosion of Carbon Steel under Controlled Laboratory Conditions

In the Iberian Pyritic Belt (SW Europe), Acid Mine Drainage (AMD) is the consequence of the interaction of physical-chemical and biological factors, where aerobic Fe and/or S oxidizing chemolithotrophic and anaerobic sulfate reducing bacteria play an essential role. As a result, the polluted waters are highly acidic (pH 2–3) and contain numerous dissolved or suspended metals, which gives them a powerful corrosive action on constructions related to mining activities with high economic losses. To verify the role of bacteria in the corrosion of carbon steel, a common material in buildings exposed to corrosion in acidic waters, several experiments have been carried out under controlled conditions using carbon steel bars and acidic water containing bacteria consortia from an AMD river of the Iberian Pyritic Belt. In all the experiments carried out, a remarkable oxidation of supplemented iron was observed in the presence of bacteria. Using carbon steel as the sole iron source, we observed a slight corrosion of the bars, but when culture media was supplemented with elemental sulfur, steel bars was severely damaged. Since the bacteria inoculum come from the surface water, well oxygenated, nutrient-poor river, the obtained results are discussed based on facultative metabolism of acidophilic chemolithotrophic bacteria.

Microorganisms in Coal Desulfurization (Review)

The information on the use of microorganisms and mixed consortia in the biological desulfurization of coal is summarized. The ecological problems that accompany the burning of high-sulfur coals are shown, and the prospects of environmentally friendly and resource-saving biotechnological approaches to coal desulfurization are considered. Analysis of available literature indicates the enormous role of microorganisms of various taxonomic groups in the removal of inorganic and organic sulfur in coals. Mesophilic and moderately thermophilic acidophilic chemolithotrophic bacteria (ACB) of the genus Acidithiobacillus—A. ferrooxidans, A. thiooxidans, A. caldus, as well as some heterotrophic bacteria Bacillus subtilis and paenibacillus polymyxa—play the dominant role in the removal of inorganic sulfur. Mixed cultures and associations of mesophilic and thermophilic bacteria isolated from coal mines or from the coal surface structure are considered an effective tool in the biosulfurization of pyrite sulfur. The prospects of microbial desulfurization of organic coal sulfur with the use of heterotrophic microorganisms of the genera Pseudomonas, Sulfolobus, Rhodococcus, the fungi Agrocybe aegerita and Alterneria sp., the bacterial–fungal consortia Sulfolobus solfataricus and Phanerochaeta chrysosporium ME446, and the laccase enzyme of the basidiomycetes Trametes versicolor ATCC 20080 are examined.

Early reprecipitation of sulfate salts in coal biodesulfurization processes using acidophilic chemolithotrophic bacteria.

This study evaluated the effect of three sulfate salt-based culture media on the reprecipitation of sulfur under the action of two types of bacterial inoculum, a pure strain of Acidithiobacillus ferrooxidans (ATCC 23270) and a consortium of this strain and Acidithiobacillus thiooxidans (ATCC 15494), in a biodesulfurization process for coal (particle size < 0.25mm) from the 'La Guacamaya' mine (Puerto Libertador, Córdoba, Colombia). All of the experiments were periodically monitored, with measurements taken of pH, cell concentration, iron concentration, and pyrite oxidation. Additionally, mineralogical analyses were conducted on the initial and final coal samples, through scanning electron microscopy with an energy-dispersive X-ray spectrometer. The results showed that sulfate reprecipitation occurred primarily, and nearly entirely, during the first 3 days of the process. While all the treatments obtained high levels of mineral oxidation, the reprecipitation processes decreased in media with low concentrations of sulfate, leading to the higher final removal of inorganic sulfur. The bioassays revealed that after 15days, the maximum pyrite oxidation (86%) and inorganic sulfur removal (53%) was obtained with the treatments using the Kos and McCready culture media. The bacteria evaluated were found to have a great ability to adapt to very simple culture media with minimal nutrient concentrations, and even with some nutrients absent (as in the case of magnesium).

ВИКОРИСТАННЯ МЕТОДІВ ДИСПЕРСІЙНОГО І КЛАСТЕРНОГО АНАЛІЗУ ДЛЯ ПОРІВНЯННЯ СТІЙКОСТІ ДО ВАЖКИХ МЕТАЛІВ АЦИДОФІЛЬНИХ ХЕМОЛІТОТРОФНИХ БАКТЕРІЙ, ВИДІЛЕНИХ ІЗ ТЕХНОГЕННОЇ СИРОВИНИ

In the present work, the resistance to heavy metals of one reference strain Acidithiobacillus ferrooxidans ATCC 23270 and eight strains of acidophilic chemolithotrophic microorganisms isolated from dump products of the fuel and energy complex of Ukraine of various types was investigated. For the study were used metals that have the property of substituents (Zn 2+ , Ni 2+ , Co 2+ ), metals of the “combined” action (Cu 2+ ), and metals that do not perform biological functions (Cd 2+ , Pb 2+ ), but which are able to form insoluble complexes on/into the cells or interact with nucleic acids. It was established that the impact of metals on the studied strains of acidophilic chemolithotrophic bacteria is ambiguous and does not correspond to the scale of interaction of metals with nitrogenous heterocyclic bases of DNA. The maximum number of strains were resistant to cobalt ions (66.6 % with an MIС value of 0.09 M). about 55.5 % of the strains were resistant to impact of copper, cadmium and zinc ions with indicators of MIC of 0.13, 0.061, and 0.083 M, respectively. A statistic analysis of obtained results of the resistance to heavy metals of acidophilic chemolithotrophic bacteria with used using the methods of dispersion and cluster analyzes in the R 3.4.0 program was carried out. Clustering of the results according to the minimum inhibitory concentrations allowed us to group the studied metals into three clusters: a single (Pb 2+ ), a cluster (Zn 2+ , Ni 2+ , Co 2+ , Cd 2+ ) and subcluster (Cu 2+ ). Also, hierarchical cluster analysis based on the level of resistance of strains allowed us to divide the studied strains into two groups depending on their level of resistance to metals. The strains that were isolated from coal wastes were the most resistant to the studied metals. The active systems of metal transport of studied acidophilic chemolithotrophic bacteria were theoretically predicted based on literature data analysis. The difference in the level of resistance to metals in A. ferrooxidans and A. thiooxidans was partially associated with the use of bivalent iron as an energy source. The heterogeneity of efflux systems response to the action of heavy metals within the group of microorganisms belonging to A. ferrooxidans was shown.

RESISTANCE OF ACIDOPHILIC CHEMOLYTOTROPHIC BACTERIA ISOLATED FROM TECHNOGENIC RAW MATERIALS TO HEAVY METALS

Aim. Determination of resistance to heavy metal ions of acidophilic chemolithotrophic bacteria isolated from dump products of fuel-energy complex of Ukraine. Methods. Traditional microbiological: cultivation of strains were carried out with using of Silverman-Lundgrem 9K medium in the presence of copper, zinc, nickel, cobalt and cadmium ions in the concentration range 0.5–12.0 g/dm3 at intervals 0,5 g/dm3 , in the presence of lead in the concentration range 0.25–1.50 g/dm3 at intervals 0,05 g/dm3 ; crops carried out with a stroke; cultivation of mesophilic strains was carried out at the temperature of 35.0±0.2 °C, moderately thermophilic – at 50.0±0.2 °C within seven days; the results were recorded visually by comparing the experimental options with the control ones; the control was 9K medium without metal ions. Results. The results indicate a high level of resistance of isolated strains of the genera Acidithiobacillus and Sulfobacillus to various heavy metal ions. The metals minimum inhibitory concentrations (MIC) for the studied strains were several times higher than their content in dump products of fuel-energy complex. A series of metal ions toxicity in relation to the isolated strains has been established: Pb2+ ion was the most toxic (MIC for all the strains it was in the range of 0.35–0.70 g/dm3 ), the least toxic was Cu2+ ion (MIC reached 11.5 g/dm3 ). A number of resistances of isolated acidophilic chemolithotrophic bacteria of the genera Acidithiobacillus and Sulfobacillus with respect to toxic metal ions has been determined. The strains isolated from coal waste dumps possessed the maximum resistance, the minimal strains were those isolated from coal burning wastes, as well as the typical ones. Conclusion. The strains of acidophilic chemolithotrophic bacteria isolated from technogenic raw materials belong to multiresistant ones, since they showed a high level of resistance to a wide range of heavy metal ions in a wide range of concentrations. The resistance of strains depends on their individual characteristics and sources of isolation. Identified interspecific and intraspecific differences of the strains by their resistance, is associated with various physiological and genetic factors.

Genetic variability in Acidithiobacillus spp. – a working horse of environmental biotechnologies

AbstractThe genus Acidithiobacillus comprises 7 species of Gram-negative obligatory acidophilic chemolithotrophic bacteria that derive energy mainly from the oxidation of reduced sulphur compounds. Four of the species also catalyse the dissimilatory oxidation of ferrous iron while three (A. thiooxidans, A. albertensis, and A. caldus) do not. Bacteria from the genus Acidithiobacillus are often associated with mineral biotechnologies (biomining) and acid mine drainage. While acceleration of mineral solubilisation is a positive aspect in environmental biotechnologies, it is undesirable in acid mine drainage with strong negative ecological impact and there is profound interest in genetics and genomics of these bacteria. Representatives of Acidithiobacillus genus occur world-wide, however there are limited data on Acidithiobacillus spp. variability from Slovakia. In our work the variability of Acidithiobacillus spp., from Slovakia was analysed and the presence of A ferrooxidans was detected. In addition, for the first time we report here on the occurrence of A. albertensis as well. Comparative analyses confirmed pronounced genetic and genomic diversity within the genus, especially within A. ferrooxidans and A. thioxidans complexes. Based on data presented, several Acidithiobacillus species could be considered as a complex species and the description of several new species is very probable in the near future.

Complete Genome Sequence of Acidithiobacillus ferridurans JCM 18981.

Acidithiobacillus ferridurans is an acidophilic chemolithotrophic bacterium that can grow in the presence of high concentrations of ferrous iron. Here, we present the complete 2,921,399-bp genome sequence of the strain A. ferridurans JCM 18981T, isolated from uranium mine drainage water.

BIOTECHNOLOGICAL METHODS FOR PROCESSING SUBSTANDARD ORES AND WASTES

The information about using of biotechnological methods for the processing of mineral and technogenic raw materials was analyzed and summarized in the article. A review of the main groups of microorganisms that make up the microbiocenosis of various ecological niches and wastes is given. The leading role of acidophilic chemolithotrophic bacteria in the oxidation process of natural sulphide raw materials is also shown. Basic mechanisms of bacterial leaching of metals and the influence of various factors on the efficiency of oxidation of sulfides are considered. A characteristic of the main methods of bacterial leaching – tanks, underground and heap was given and there were considered their advantages and disadvantages. The article gives the world examples of the use of bioleaching for the production of copper, nickel, gold, uranium. It is noted that there is no practical application of bacterial leaching for processing technogenic raw materials, in particular, coal and energy industry waste for the extraction of valuable metals – germanium, gallium, etc.

BACTERIAL LEACHING OF THE METALS FROM THE SPENT MASS OF FUEL ELEMENTS

Aim. To establish the possibility of bacterial leaching of zinc and manganese from the electrode mass of spent batteries. Methods. To determine the growth of acidophilic chemolithotrophic bacteria of acidophilic chemolithotrophic bacteria(ACB) there were used the media of different component and concentration composition. Ferrous iron and thiosulfate were used as energy sources. The amount of cells was determined by seeding on solid medium after tenfold serial dilutions. Stained microscopic preparation was examined by light microscopy. The method of atomic absorption spectroscopy with using AAS-1, S-115PK Selmi instruments was used to determine the content of metals in solutions. The results of determining the structural analysis of the electrode mass of spent batteries were recorded on a URS-50IM diffractometer. Results. The possibility of using AHB for leaching manganese and zinc from the electrode mass of spent batteries was established. The maximum metal leaching within a week was recorded when there were used the media 9K1 with ferrous iron at concentration of 44.5 g/dm3. When extending the term of leaching to a forthnight there were registered high intensity of biological leaching of the metals from electrode mass of spent batteries only in case of using the nutrient medium No. 15. It was shown that the using of the suspension Acidithiobacillus ferroooxidans MF Lv 7 increases the degree of manganese extraction to 30.0%, and zinc to 99.8%. The differences in the structure of the electrode mass of spent batteries before and after bacterial leaching, namely the absence of ZnO and MnO, decrease in the amount of MnO2, increase in Mn2O3, and appearance of Mn3O4 has been shown with help of X-ray diffraction analysis. Conclusions. The possibility of using ACV for bacterial leaching of metals from the electrode mass of spent batteries was shown. The obtained results make it possible to additionally getting zinc and manganese and preventing environmental pollution by environmentally hazardous compounds.

Isolation and study of the main properties of acidophilic chemolithotrophic bacteria isolated from the waste dumps of fuel-energy complex in Ukraine

Isolation and study of the main properties of acidophilic chemolithotrophic bacteria isolated from the waste dumps of fuel-energy complex in Ukraine

Improvement of metals leaching optimal parameters from technogenic waste dumps with using mesophilic association of acidophilic chemolithotrophic bacteria

The results of improving the standard parameters of the process of bacterial leaching of metals, which allow to shorten the term of carrying out technological process and increase the efficiency of the extraction of germanium and other useful components are provided in article. To achieve the goal the mineralogical and chemical analysis of waste dumps have been made and the composition and leaching potential of the main groups of microorganisms of waste dumps were established also. Bacterial leaching was carried out using the mesophilic association of acidophilic chemolithotrophic bacteria, which are characterized by a high level of leaching activity. To determine the optimal parameters of the biotechnological process were compared results obtained with used: standard 9K medium with ferrous iron as an energy source; at constant elevated values of the oxidation-reduction potential at the level of 0.650 V; with ferric iron as an oxidizing agent, and using an optimized nutrient medium (OPM), the composition of which has been determined on the basis of mathematical optimization. The obtained results showed, that the using of ferric iron, OPM and elevated values the oxidation-reduction potential allow to shorten the term of leaching process and increase the recovery of germanium and other metals by 2 to 5 times. Moreover, the advantage of leaching with OPM is the absence of iron ions, which are an impurity and interfere with further sorption recovery of germanium from polymetallic solutions to produce germanium concentrate. Thus, optimum process parameters of bacterial leaching of metals, allows using them depending on the conditions and needs receiving of the targets metals from waste dumps.

BACTERIAL DESULPHURIZATION OF COALS

The review contains literature data about the amount of various forms of sulfur in coals and its impact on the qualitative characteristics of coal. The technological and environmental problems resulting from the combustion of high-sulfur coals are shown. The problems of coal enrichment are considered and an overview of modern methods for their desulfurization are presented. Particular attention is paid to the biotechnological methods with using microorganisms of various taxonomic groups. Data about the reduction of sulphur content in the coals, mainly pyrite, under the action by representatives of mesophilic and moderately thermophilic acidophilic chemolithotrophic bacteria are given. A comparative analysis of the ability of the bacteria of the genera Pseudomonas, Bacillus, Brevibarterium and others to destroy the sulfur-containing heteroatom included in the structural matrix of coal are else given. The data on the role of heterotrophic bacteria in the oxidation of organic sulfur are shown.

Composition of aboriginal consortium of microorganisms from coal mines dumps

The article presents the results of studies aimed at characterictics of quantitative and qualitative composition of aboriginal consortium of microorganisms from coal mines dumps of Lviv-Volynsky coal-basin with different storage time. The defined qualitative composition of substrates’ microbiocenosis does not depend on the storage time, because it builds up in a course of substrates’ formation and is defined by already established chemical and mineralogical composition of the dumps. It was confirmed that he­terotrophic and acidophilic chemolithotrophic bacteria, namely mesophilic and mode­rately thermophilic genera Acidithiobacillus and Sulfobacillus, are present in the aboriginal consortium of substrates from coal mines dumps . Isolation of the acidophilic chemolithotrophic bacteria from substrates with neutral pH (from the dumps under study) proves that spreading of these bacteria is much wider than that of naturally aci­dic ecosystems. It was stated that the neutrophilic thionic and sulphate-reducing bacteria are present in the composition of the microbial association of the studied dumps. The existence of sporulated “silicate” bacteria capable of breaking quartz in the heterotrophic component of microbiocenosis was also confirmed. The study proved that representatives of different groups of microorganisms of the aboriginal microbiota prevail quantitatively in the dumps with long storage time. This is a consequence of substrates’ transformations in a course of storage under the exposure to exogenous factors that, in their turn, leads to a greater display of biocenosis in the substrates.

Microbial removal of toxic metals from a heavily polluted soil

Samples of a leached cinnamonic forest soil heavily polluted with uranium and some toxic heavy metals (mainly copper, zinc and cadmium) were subjected to cleaning by means of bioleaching with acidophilic chemolithotrophic bacteria. The leaching of the soil was performed by stimulating the activity of these bacteria to leach and remove the pollutants from the horizon A to the deeply located horizon B2 in which pollutants were precipitated by stimulating the activity of the indigenous sulphate-reducing bacteria. The treatment was carried out in a green house in which several plots containing 150kg of soil each were constructed. The effect of some essential environmental factors such as pH, humidity, temperature and contents of nutrients on the cleaning process was studied. It was found that under optimal conditions the content of pollutants were decreased below the relevant permissible levels within a period of 170days. The soil cleaned in this way was characterized by a much higher production of biomass of different plants (alfalfa, clover, red fescue, vetch) than the untreated polluted soil.

Prevention of the Generation of Acid Mine Drainage in a Dump Rich-In Pyrite Uranium Ore

The uranium deposit Curilo, Bulgaria for a long period of time was a site of intensive industrial-scale leaching of uranium and recovery of primary uranium-bearing concentrates. These activities were ceased twenty five years ago and since that time and until recently the deposit was, especially after rainfall, a huge site of spontaneous generation of acid mine drainage containing uranium, its radioactive disintegration products and several toxic heavy metals. This process was mainly due to the activity of the indigenous acidophilic chemolithotrophic bacteria which oxidized the pyrite, other sulphides and uranium - bearing minerals present in the deposit. Different methods to prevent the generation of such polluted waters were applied but the best results were achieved by construction of a specific rich-in-organics and crushed limestone soil cover on the surface of one of the waste dumps in the deposit.

Biooxidation of Carbonaceous Refractory Gold Ores by an Iron-Sulfur-Oxidizing Mixotrophic Bacterium at Neutral pH

The ability of an iron-sulfur-oxidizing mixotrophic bacterium to treat two types of sulfide-rich carbonaceous refractory gold concentrates from Sulawesi and Sumatra in Indonesia was studied in comparison with an acidophilic chemolithotrophic bacterium Acidithiobacillus ferrooxidans. Over the course of the biooxidation experiments, the pH of the solution tended to rise (pH&gt;5) due to the high content of acid-consuming minerals such as carbonates in both concentrates. Ferric ions were frequently observed to precipitate due to high solution pH. The BIOXskc employed in this study was able to increase the gold extraction from low sulfidic carbonaceous refractory gold concentrates by ~15% higher than that by using At. ferrooxidans. It was also capable of treating carbonaceous matters which causes preg-robbing effect and retaining iron in ionic form due presumably to the production of extracellular polymeric substances (EPS) under high solution pH. Nevertheless, BIOXskc also reduced the gold extraction yield of high sulfidic gold concentrates because of passivation effect. It is suggested that the precipitation of iron and sulfur on the surface of sulfide minerals during biooxidation may prevent cyanide ion contact with gold.

Study and assessment of microbial communities in natural and commercial bioleaching systems

The exceptional diversity of ecogeographical conditions of Armenia and the richness of non-ferrous metals represent a great and valuable potential for the investigation of the biodiversity of acidophilic chemolithotrophic bacteria as well as for the isolation of new highly efficient strains and their communities. The studies of physiological and biotechnological properties of these relevant strains from the bioleaching communities will allow us to achieve comprehensive insight of interspecies relationships as a substantial prerequisite for the enhancement of the efficiency of biohydrometallurgical processes.In this study, novel strains of acidophilic chemolithotrophic bacteria belonging to genera Acidithiobacillus as well as Leptospirillum and Sulfobacillus have been isolated from sulfide ores of different geoformations in Armenia. The results showed that: (1) high efficiency of the isolated bacteria in bioleaching of pyrite was determined by their biochemical properties, especially enzyme activities involved in oxidation of ferrous iron and reduced inorganic sulfur compounds (RISCs). (2) Bioleaching of pyrite was directly connected with the ability of isolated strains to adhere on pyrite surfaces. Moreover, the efficiency of bioleaching of pyrite was correlated with the amount of adhered/attached bacterial cells of the isolated strains.

Extraction of copper from an oxidized (lateritic) ore using bacterially catalysed reductive dissolution

An oxidized lateritic ore which contained 0.8 % (by weight) copper was bioleached in pH- and temperature-controlled stirred reactors under acidic reducing conditions using pure and mixed cultures of the acidophilic chemolithotrophic bacterium Acidithiobacillus ferrooxidans. Sulfur was provided as the electron donor for the bacteria, and ferric iron present in goethite (the major ferric iron mineral present in the ore) acted as electron acceptor. Significantly more copper was leached by bacterially catalysed reductive dissolution of the laterite than in aerobic cultures or in sterile anoxic reactors, with up to 78 % of the copper present in the ore being extracted. This included copper that was leached from acid-labile minerals (chiefly copper silicates) and that which was associated with ferric iron minerals in the lateritic ore. In the anaerobic bioreactors, soluble iron in the leach liquors was present as iron (II) and copper as copper (I), but both metals were rapidly oxidized (to iron (III) and copper (II)) when the reactors were aerated. The number of bacteria added to the reactors had a critical role in dictating the rate and yield of copper solubilised from the ore. This work has provided further evidence that reductive bioprocessing, a recently described approach for extracting base metals from oxidized deposits, has the potential to greatly extend the range of metal ores that can be biomined.

Decreasing the contamination and toxicity of a heavily contaminated soil by in situ bioremediation

Experimental plot consisting of acidic leached cinnamonic forest soil heavily contaminated with radionuclides (mainly U and Ra) and non-ferrous metals (mainly Cu, Zn and Cd) was treated in situ under real field conditions using the activity of the indigenous soil microflora. This activity was enhanced by suitable changes of some essential environmental factors such as pH and water, oxygen and nutrient contents of the soil. The treatment was connected with solubilization and removal of contaminants from the top soil layers (horizon A) due to the joint action of the soil microorganisms and leach solutions used to irrigate the soils (mainly acidophilic chemolithotrophic bacteria and diluted sulphuric acid). The dissolved contaminants were transferred through the drainage soil effluents to the deeply located soil subhorizon B2 where they were precipitated as the relevant insoluble forms (uranium as uraninite, and the non-ferrous metals as the relevant sulphides) as a result of the activity of the sulphate-reducing bacteria inhabiting this soil subhorizon. The effluents from the subhorizon B2 containing much lower concentrations of inorganic contaminants but enriched in dissolved biodegradable organics were subjected to additional treatment in a constructed wetland for removing these residual contaminants. It was also demonstrated that an efficient treatment of the effluents from the subhorizon B2 could be achieved by a microbial fuel cell in which the cleanup was connected with electricity generation.

Heterodisulfide Reductase from &lt;i&gt;Acidithiobacilli&lt;/i&gt; is a Key Component Involved in Metabolism of Reduced Inorganic Sulfur Compounds

Heterodisulfide reductase (Hdr), is an iron-sulfur protein which in anaerobic methanogenic archaea catalyzes the reduction of the disulphide bond between coenzyme M and coenzyme B and is coupled to methane formation. In aerobic acidophilic chemolithotrophic bacteria (e.g., biomining bacteria) the function of this enzyme is unclear. Inspection of the genomic sequences of Acidithiobacillus ferrooxidans DSM 16786 and Acidithiobacillus thiooxidans DSM 17318 and reverse transcriptase-PCR results revealed a cluster of six co-transcribed genes, hdrC1, hdrB1, hdrA, orf1, hdrC2 and hdrB2, encoding proteins with high similarity to catalytic Hdr subunits. Additionally, microarray expression profiling and quantitative RT-PCR experiments demonstrated that the hdr genes of A.ferrooxidans and A. thiooxidans were highly expressed when bacteria are grown in the presence of sulfur and tetrathionate. Moreover, hdr genes in A. ferrooxidans were greatly up-regulated when this microorganism was grown in sulfur compared to ferrous medium. These results strongly support a role for Hdr in oxidative metabolism of reduced sulfur compounds in aerobic chemolithotrophic bacteria.