Bioleaching Process for Copper Extraction from Waste in Alkaline and Acid Medium

Flotation wastes are becoming a valuable secondary raw material and source of many metals and semimetals worldwide with the possibilities of industrial recycling. The flotation tailings contain oxide and sulfide minerals that have not been sufficiently stabilized and form acidic mine waters, which in turn contaminate groundwater, rivers, and reservoi6sediments. An effective way to recycle these mine wastes is to recover the metals through leaching. While the focus is on acid bioleaching by iron- and sulfur-oxidizing bacteria, alkaline leaching, and the removal of iron-containing surface coatings on sulfide minerals contribute significantly to the overall environmental efficiency of leaching. For this study, static and percolate bioleaching of copper from flotation waste at the Bor copper mine in Serbia was investigated in alkaline and then acidic environments. The aim of the study was to verify the effect of alkaline pH and nutrient stimulation on the bioleaching process and element extraction. A sample was taken from a mine waste site, which was characterized by XRF analyses. The concentration of leached copper was increased when copper oxide minerals dissolved during alkaline bioleaching. The highest copper yield during alkaline bioleaching was achieved after 9 days and reached 67%. The addition of nutrients in acidic medium enhanced the degradation of sulfide minerals and increased Cu recovery to 74%, while Fe and Ag recoveries were not significantly affected. Combined bioleaching with alkaline media and iron- and sulfur-oxidizing bacteria in acidic media should be a good reference for ecological Cu recovery from copper oxide and sulfide wastes.

Isolation, characterization and S2−-oxidation metabolic pathway of a sulfur-oxidizing strain from a black-odor river in Beijing

A single strain capable of efficient S2−-oxidizing was isolated from a black-odor river in Beijing. The single strain was identified as Stenotrophomonas through the physiology and biochemical characteristics as well as the 16S rRNA sequencing experiment. This strain was named as Stenotrophomonas sp.sp3 (strain sp3). The experimental results showed that for the strain sp3 growth and S2− oxidization, the optimal conditions were as follows: 25 °C of temperature, initial pH 7, 2.5 g/L of initial glucose concentration and 1.00 g/L of initial cell concentration. It was found that there were 31 kinds of sulfur oxidation related genes in the strain sp3 through the whole genomic analysis. The results of the transcriptome analysis suggested that the main metabolic pathway of S2− to SO42− was the paracoccus sulfur oxidation process. The bioconversion processes of S2− to S0, S2− to SO32−, S2O32− to S0 and SO32−, and SO32− to SO42− were controlled by hdrA, cysIJ, tst and sox gene, respectively.

Draft Genome Sequences of Sulfurovum spp. TSL1 and TSL6, Two Sulfur-Oxidizing Bacteria Isolated from Marine Sediment

Sulfurovum spp. TSL1 and TSL6 are sulfur-oxidizing chemolithoautotrophic bacteria isolated from the tsunami-launched marine sediment in the Great East Japan earthquake. This announcement describes the draft genome sequences of the two isolates that possess the gene sets for the sulfur oxidation pathway.

The pathway of sulfide oxidation to octasulfur globules in the cytoplasm of aerobic bacteria

Sulfur-oxidizing bacteria can oxidize hydrogen sulfide (H 2 S) to produce sulfur globules. Although the process is common, the pathway is unclear. In recombinant Escherichia coli and wild-type Corynebacterium vitaeruminis DSM20294 with SQR but no enzymes to oxidize zero valence sulfur, SQR oxidized H 2 S into short-chain inorganic polysulfide (H 2 S n , n≥2) and organic polysulfide (RS n H, n≥2), which reacted with each other to form long-chain GS n H (n≥2) and H 2 S n before producing octasulfur (S 8 ), the main component of elemental sulfur. GS n H also reacted with GSH to form GSnG (n≥2) and H 2 S; H 2 S was again oxidized by SQR. After GSH was depleted, SQR simply oxidized H 2 S to H 2 S n , which spontaneously generated S 8 . S 8 aggregated into sulfur globules in the cytoplasm. The results highlight the process of sulfide oxidation to S 8 globules in the bacterial cytoplasm and demonstrate the potential of using heterotrophic bacteria with SQR to convert toxic H 2 S into relatively benign S 8 globules. IMPORTANCE Our results support a process of H 2 S oxidation to produce octasulfur globules via SQR catalysis and spontaneous reactions in the bacterial cytoplasm. Since the process is an important event in geochemical cycling, a better understanding facilitates further studies and provides theoretical support for using heterotrophic bacteria with SQR to oxidize toxic H 2 S into sulfur globules for recovery.

HCH Removal in a Biochar-Amended Biofilter

This study evaluated the efficiency of two biofilter systems, with and without biochar chambers installed, at degrading and removing HCH and its isomers in natural drainage water. The biochar biofilter proved to be 96% efficient at cleaning HCH and its transformation products from drainage water, a significant improvement over classic biofilter that remove, on average, 68% of HCH. Although iron- and sulfur-oxidizing bacteria, such as Gallionella and Sulfuricurvum, were dominant in the biochar bed outflows, they were absent in sediments, which were rich in Simplicispira, Rhodoluna, Rhodoferax, and Flavobacterium. The presence of functional genes involved in the biodegradation of HCH isomers and their byproducts was confirmed in both systems. The high effectiveness of the biochar biofilter displayed in this study should further encourage the use of biochar in water treatment solutions, e.g., for temporary water purification installations during the construction of other long-term wastewater treatment technologies, or even as final solutions at contaminated sites.

Differential Regulation of Degradation and Immune Pathways Underlies Adaptation of the Ectosymbiotic Nematode Laxus Oneistus to Oxic-Anoxic Interfaces

Eukaryotes may experience oxygen deprivation under both physiological and pathological conditions. Because oxygen shortage leads to a reduction in cellular energy production, all eukaryotes studied so far conserve energy by suppressing their metabolism. However, the molecular physiology of animals that naturally and repeatedly experience anoxia is underexplored. One such animal is the marine nematode Laxus oneistus. It thrives, invariably coated by its sulfur-oxidizing symbiont Candidatus Thiosymbion oneisti, in anoxic sulfidic or hypoxic sand. Here, transcriptomics and proteomics showed that, whether in anoxia or not, L. oneistus mostly expressed genes involved in ubiquitination, energy generation, oxidative stress response, immune response, development, and translation. Importantly, ubiquitination genes were also highly expressed when the nematode was subjected to anoxic sulfidic conditions, together with genes involved in autophagy, detoxification and ribosome biogenesis. We hypothesize that these degradation pathways were induced to recycle damaged cellular components (mitochondria) and misfolded proteins into nutrients. Remarkably, when L. oneistus was subjected to anoxic sulfidic conditions, lectin and mucin genes were also upregulated, potentially to promote the attachment of its thiotrophic symbiont. Furthermore, the nematode appeared to survive oxygen deprivation by using an alternative electron carrier (rhodoquinone) and acceptor (fumarate), to rewire the electron transfer chain. On the other hand, under hypoxia, genes involved in costly processes (e.g., amino acid biosynthesis, development, feeding, mating) were upregulated, together with the worm’s Toll-like innate immunity pathway and several immune effectors (e.g., Bacterial Permeability Increasing proteins, fungicides). In conclusion, we hypothesize that, in anoxic sulfidic sand, L. oneistus upregulates degradation processes, rewires oxidative phosphorylation and by reinforces its coat of bacterial sulfur-oxidizers. In upper sand layers, instead, it appears to produce broad-range antimicrobials and to exploit oxygen for biosynthesis and development.

Giant sulfur bacteria (Beggiatoaceae) from sediments underlying the Benguela upwelling system host diverse microbiomes

Due to their lithotrophic metabolisms, morphological complexity and conspicuous appearance, members of the Beggiatoaceae have been extensively studied for more than 100 years. These bacteria are known to be primarily sulfur-oxidizing autotrophs that commonly occur in dense mats at redox interfaces. Their large size and the presence of a mucous sheath allows these cells to serve as sites of attachment for communities of other microorganisms. But little is known about their individual niche preferences and attached microbiomes, particularly in marine environments, due to a paucity of cultivars and their prevalence in habitats that are difficult to access and study. Therefore, in this study, we compare Beggiatoaceae strain composition, community composition, and geochemical profiles collected from sulfidic sediments at four marine stations off the coast of Namibia. To elucidate community members that were directly attached and enriched in both filamentous Beggiatoaceae, namely Ca. Marithioploca spp. and Ca. Maribeggiatoa spp., as well as non-filamentous Beggiatoaceae, Ca. Thiomargarita spp., the Beggiatoaceae were pooled by morphotype for community analysis. The Beggiatoaceae samples collected from a highly sulfidic site were enriched in strains of sulfur-oxidizing Campylobacterota, that may promote a more hospitable setting for the Beggiatoaceae, which are known to have a lower tolerance for high sulfide to oxygen ratios. We found just a few host-specific associations with the motile filamentous morphotypes. Conversely, we detected 123 host specific enrichments with non-motile chain forming Beggiatoaceae. Potential metabolisms of the enriched strains include fermentation of host sheath material, syntrophic exchange of H2 and acetate, inorganic sulfur metabolism, and nitrite oxidation. Surprisingly, we did not detect any enrichments of anaerobic ammonium oxidizing bacteria as previously suggested and postulate that less well-studied anaerobic ammonium oxidation pathways may be occurring instead.

Differential regulation of degradation and immune pathways underlies adaptation of the symbiotic nematode Laxus oneistus to oxic-anoxic interfaces

Eukaryotes may experience oxygen deprivation under both physiological and pathological conditions. Because oxygen shortage leads to a reduction in cellular energy production, all eukaryotes studied so far conserve energy by suppressing their metabolism. However, the molecular physiology of animals that naturally and repeatedly experience anoxia underexplored. One such animal is the symbiotic marine nematode Laxus oneistus. It thrives, invariably coated by its sulfur-oxidizing bacterium Candidatus Thiosymbion oneisti, in anoxic sulfidic or hypoxic sand. Here, transcriptomics and proteomics showed that, whether in anoxia or not, L. oneistus mostly expressed genes involved in ubiquitination, energy generation, oxidative stress response, immune response, development, and translation. Importantly, ubiquitination genes were also highly expressed when the nematode was subjected to anoxic sulfidic conditions, together with genes involved in autophagy, detoxification, chaperone-encoding genes, and ribosome biogenesis. We hypothesize that these degradation pathways were induced to recycle damaged cellular components (mitochondria) and misfolded proteins into nutrients. Remarkably, when L. oneistus was subjected to anoxic sulfidic conditions, lectin genes were also upregulated, potentially to promote the attachment of its thiotrophic anaerobic symbiont. Furthermore, L. oneistus appeared to survive oxygen deprivation by using an alternative electron carrier (rhodoquinone) and acceptor (fumarate), to rewire the electron transfer chain. On the other hand, under hypoxia, genes involved in costly processes (e.g., amino acid biosynthesis, development, feeding, mating) were upregulated, together with the worm's Toll-like innate immunity pathway and several immune effectors (e.g., Bacterial Permeability Increasing proteins, fungicides). In conclusion, we hypothesize that, in anoxic sulfidic sand, L. oneistus survives by overexpressing degradation processes, rewiring oxidative phosphorylation and by reinforcing its coat of bacterial sulfur-oxidizers. In upper sand layers, instead, it appears to produce broad-range antimicrobials and to exploit oxygen for biosynthesis and development.