Advanced Materials Research Vols. 71-73

Abstract: The aim of this review report was to summarize knowledge about arsenic-metabolizing bacteria isolated from Zloty Stok (SW Poland) gold mine and determine their potential role in mobilization of arsenic. Three physiologically different groups of arsenic metabolizing microorganisms (arsenite oxidizers, dissmiliatory arsenate reducers and arsenic resistant microbes) were isolated from the deepest section of Gertruda Adit in Zloty Stok (SW Poland) gold mine. Twenty two strains were isolated from the rock biofilms and seven from arsenic-rich bottom sediments. Analysis of the 16S rRNA gene sequence of isolated bacteria revealed them to be members of the genera: Aeromonas, Arthrobacter, Bacillus, Brevundimonas, Chryseobacterium, Desemzia, Microbacterium, Micrococcus, Paracoccus, Pseudomonas, Rhodococcus, Serratia, Shewanella, Sinorhizobium, Sphingomonas, Stenotrophomonas and Streptomyces. All of the isolated bacteria were resistant to both inorganic arsenic species: arsenate [As(V)] and arsenite [As(III)]. One of the bottom sediments isolates (Sinorhizobium sp. M14) was able to grow on minimal salt medium using arsenite as a source of energy, and was able to release arsenic from arsenopyrite. Two strains (Shewanella sp. O23S and Aeromonas sp. O23A) isolated from bottom sediments were able to grow in the absence of oxygen, by As (V) respiration coupled with lactate oxidation. Based on arsenic metabolic activity of isolated bacteria two different mechanisms of arsenic mobilization from natural minerals (arsenopyrite FeAsS) and secondary ferrous arsenate minerals (scorodite FeAsO4) were proposed.

Abstract: The capacity of a microbiological mine water treatment plant may to be enhanced by understanding the microbiological processes. Therefore different samples from the pilot plant were analyzed by culture-independent and cultivation methods. Dominant bacteria could be isolated on overlay plates or enriched in gradient cultures. To immobilize biomass in the pilot plant, various carrier materials were tested. Sessil, the material currently used in the pilot plant, was the most favored and appropriate material.

Abstract: When bauxite is digested during Bayer processing, associated organic compounds and humic acids are degraded to produce sodium salts of organic acids, including sodium oxalate. If not removed from the liquor stream, sodium oxalate co-precipitates with the aluminium hydroxide resulting in poor crystallization and alumina and soda loss. Aerobic bioremediation processes have been developed as an economic and environmentally sound option for oxalate removal. Little research has been directed at characterising the microbial communities and biological processes underpinning these processes. Analysis of samples from both a moving bed biofilm reactor and bioreactor effluent using PCR-DGGE of 16S rRNA genes showed microorganisms of the genus Halomonas dominated the process. Most Probable Number (MPN) analyses also showed Halomonas spp. to be numerically dominant in all bioreactor samples.

Abstract: Corrosion is the destructive effect of environment on metals and alloys. Corrosion is a spontaneous phenomenon which causes metal conversion from zero oxidation degree to a species with high oxidation degree. As a result of this chemical interaction due to the corrosion phenomenon, irretrievable damages are made to the equipment and installations of various industries. Biocorrosion has occurred in the water supply pipes at Sarcheshmeh copper mine(Located in South of Iran), and in order to assess the amount of biocorrosion and remove these biological interactions we decided to chemically evaluate the water sample in the water supply pipelines at this mine. In this look, the water sample exist in the water supply pipelines at Sarcheshmeh copper mine was studied, sulfur corrosive bacteria were separated and identified and their biochemical activity was researched and studied and it was found that the target species are in fact Sulfolobus bacteria which have different enzymatic activities. Due to these enzymatic activities, a considerable amount of sulfur is accumulated on the cell surface. Based on various incubation environments, as a result of sulfur accumulation, Sulfolubos bacteria were identified.

Abstract: Alkaliphilic sulfur-oxidizing bacteria were isolated from an alkaliphilic microbial consortium used to treat H2S at pH>9 in a laboratory scale biofilter. Nineteen isolates were obtained. These isolates could be grouped based on their colonial morphology on a solid medium containing thiosulfate as sole energy source. Half of the isolates presented yellow colonies (group I). This yellowish colonial morphology is typically found in the genus Thioalkalivibrio. For the rest of the isolates, the colonies were white (group II) or transparent (group III). The isolates of each group were characterized by ribosomal intergenic spacer analysis and restriction analysis of their 16S rRNA genes. One of the yellow isolates presented 85% of homology with Thioalkalivibrio jannaschii by partial sequencing of its 16S rRNA gene. The genus Thioalkalivibrio comprises extremely haloalkaliphilic sulfur-oxidizing bacteria that have been proposed as suitable biocatalysts for natural gas desulfurization.

Abstract: The metabolic potential of 16 bioleaching microorganisms (Eubacteria and Archaea) has been investigated, allowing the prediction of potential inter- and intra-species physiological interactions (ecophysiology) during spatial and temporal changes that are known to occur within industrial bioleaching heaps. Genome analysis has allowed preliminary models to be built for genes and pathways involved in key processes such as nitrogen and carbon cycling, sulfur and iron uptake and homeostasis, extra-cellular polysaccharide biosynthesis, heavy metal resistance and energy metabolism. This paper will focus on the diverse ways that microorganisms obtain carbon from their environment with a particular emphasis on elucidating how these processes might be expected to vary over space and time during the lifetime of a bioleaching operation. It is anticipated that this knowledge will improve our understanding of fundamental biological processes in extremely acidic environments and it is hoped that it will capture usable knowledge that can be applied to bioleaching. Comparative genomics between two strains of Acidthiobacillus ferrooxidans highlights the importance of lateral gene transfer in increasing genetic and metabolic potential and suggests that classical molecular DNA techniques, such as rDNA typing, significantly underestimate the microbial diversity of bioleaching heaps.

Abstract: The role of biomolecules in bioleaching of copper sulphide minerals carried out by bacterial consortia with predominating acidithiobacilli species is of outmost interest. The proteomic analysis on bioleaching bacterial strains have been focused up to date on full Acidithiobacillus ferrooxidans proteome, allowing the identification of proteins belonging to the general stress response, phosphate limiting conditions and the ones linked to the periplasmic fraction. Our study shows for the first time the differential expression of secreted proteins by means of standard proteomics between pure cultures of Acidithiobacillus thiooxidans and in mixture with A. ferroxidans (metasecretome) grown in sulfur, where a set of proteins is de novo synthesized in the mixed culture, identifying an Omp40-like protein possibly related to bacterial adhesion, an hypothetical protein PSEEN2944 with unknown function and up-regulation of a cytochrome c biogenesis protein, findings that give an insight into the role of proteins at the sulfur – bacteria interface, highlighting the outputs of bacterial interactions in biomining environments at the protein secretion level.

Abstract: Results from a high density microarray having 32,392 50-mer oligonucleotides, termed BMS2.1, were analyzed and used for the design of a new slide, called BMS 3.0, with 560 specific oligonucleotides manufactured in standard slides to be used in any open platform. Hybridizations of several samples, either known microorganisms or environmental samples, were performed. Automatic microarray analysis software was built in order to handle these data in a quick an efficient way. While oligonucleotides designed for microorganisms with known genome sequence showed a very good behavior, according to predicted design, variations were detected when different strains were hybridized, probably due to inadequate specificity of probes. Appropriate parameterization of the analysis software will improve prediction of presence for most of the microorganisms.

Abstract: Various methods of nucleic acid (NA) extraction were investigated with the aim of developing a quantitative method of NA extraction from five representative strains of biomining microorganisms. The process of removing cells from mineral surfaces, lysing microorganisms, precipitating NA and purifying RNA were analysed. The success of each method was examined spectrophotometrically, by agarose gel electrophoresis and PCR or quantitative real time PCR (qPCR). The most important step was shown to be cellular lysis, which principally impacted on the quantity of NA extracted from each strain. The quantity and quality of extracted NA was highly dependent on the method of NA precipitation. This study resulted in the development of a NA extraction method that reliably and reproducibly extracted NA from five strains of biomining microorganisms.

Abstract: The acidophilic and strictly chemolithoautotrophic bacterium Acidithiobacillus ferrooxidans oxidizes ferrous (Fe(II)) to ferric (Fe(III)) iron and reduced inorganic sulfur compounds (RISC) to sulfuric acid, in oxic conditions. The redox proteins involved in the electron transfer between Fe(II) and oxygen are encoded in the same transcriptional unit, the rus operon. The expression of this operon is induced in the presence of Fe(II), but not Fe(III), and is not repressed in the presence of sulfur (S0). A number of genes differentially expressed in iron or sulfur conditions have been identified by microarrays transcript profiling. We show here that the presence of Fe(II) induced the expression of the genes involved in iron oxidation and repressed the expression of the genes involved in RISC oxidation. Identification of the regulator(s) involved in this transcriptional regulation is underway. Two genes encoding putative regulators belonging to two transcriptional units located downstream from the rus operon have been cloned. One regulator with a putative ironsulfur cluster belongs to the IscR family and the other belongs to the two component sensor/regulator family. Expression of both genes is induced in the presence of Fe(II) and is not repressed by S0. The recombinant proteins have been purified and gel shift assays with the target regulatory regions are in progress.