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Effect of temperature (a) at pH 1.6) and pH (b) at temperature 40 °C on iron oxidation by L. ferriphilum CC.
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A strain of Leptospirillum sp. CC previously isolated from Akhtala polymetallic ore (Armenia) was studied. The main morphological and physiological characteristics of CC were revealed. The optimal growth temperature was 40 °C and optimal pH 1.5. A phylogenetic analysis based on 16S rRNA gene sequences (GenBank ID OM272948) showed that isolate CC wa...
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A new strain of Leptospirillum sp. Ksh-L was isolated from a dump-bioleaching system of the Kashen copper-molybdenum mine (South Caucasus). Ksh-L is an obligate chemolithoautotroph, capable of oxidizing ferrous iron (Fe²⁺). Cells are Gram-negative and vibrio- or spirillum-shaped of a 0.5–3 µm size. The optimal conditions for the growth are 35 °C an...
Citations
... are distributed in natural and industrial environments where the accelerated oxidation of sulfide ores creates acidic, metal-rich ecosystems (Schippers et al., 2014). Although L. ferriphilum is the only recognized Leptospirillum species with a temperature optimum of 37°C, many isolated strains are defined as being moderately thermophilic (Dopson and Johnson, 2012;Vardanyan et al., 2023;Casas-Vargas et al., 2024). The Sulfobacillus genus is composed by species able to use elemental sulfur, ISC, and iron(II) ions as energy sources under aerobic chemolithoautotrophic or mixotrophic conditions (Golovacheva and Karavaiko, 1978;Karavaiko et al., 1988;Norris et al., 1996). ...
Biomining is a sustainable alternative to conventional mineral processing that uses acidophilic microorganisms to catalyze the extraction of valuable metals from sulfide minerals. Mixed microbial consortia composed of moderate thermophiles such as Sulfobacillus and some Leptospirillum species improve metal extraction efficiency at higher temperatures compared to pure cultures of mesophiles. However, quorum sensing (QS), which regulates microbial interactions and likely influences bioleaching performance, has not been studied in these species. In this study, treatment of a moderately thermophilic biomining consortium with QS compounds, termed diffusible signal factors (DSF), reduced pyrite and chalcopyrite dissolution via an inhibitory effect on iron oxidation and mineral colonization by the mixed culture. Furthermore, QS molecules changed the distribution of planktonic/mineral subpopulations of the acidophilic species. In addition, DSF compounds induced Acidithiobacillus caldus motility and dispersion from pyrite with a concomitant expansion of Leptospirillum ferriphilum on the mineral surface while in contrast, the acyl-homoserine lactone mediated QS system repressed L. ferriphilum motility. Moreover, the addition of QS molecules induced a second response related to the detrimental effect of high concentrations of fatty acids on cells, with an activation of detoxification mechanisms. Overall, QS regulated key target microbial interactions that opens the possibility to improve chalcopyrite bioleaching in the studied consortia.
... Liu et al. used moderate thermophiles to bioleach pyrite and achieved pyrite leaching rates of up to 91.14 % [16]. Vardanyan et al., using Leptospirillum ferriphilum CC to bioleach pyrite, extracted 91.4% of iron [17]. The mixed culture shows a higher bioleaching rate than pure culture, showing different dominant strains during diverse cultures [17]. ...
... Vardanyan et al., using Leptospirillum ferriphilum CC to bioleach pyrite, extracted 91.4% of iron [17]. The mixed culture shows a higher bioleaching rate than pure culture, showing different dominant strains during diverse cultures [17]. Thus, to improve the bioleaching rate, it is necessary to determine the success of the microbial community. ...
Sulfides should be removed before the recovery of cassiterite from tin-rich minerals due to their similarity in flotation properties. However, the traditional methods used have low selectivity. Therefore, moderately thermophilic microorganisms were used to desulfurize tin ore in this study, and the success of the microbial community was investigated. The bio-desulfurization rate reached 90% on the 10th day using the mixed culture of Leptospirillum ferriphilum (L. ferriphilum), Sulfobacillus thermosulfidooxidans (S. thermosulfidooxidans), and Acidithiobacillus caldus (A. caldus), while the pure culture needs at least 14 days. The results of X-ray Diffraction (XRD) and Inductively Coupled Plasma show that the sulfides were nearly fully solubilized. XRD results showed no pyrite in the residue, indicating that pyrite was almost fully removed while cassiterite was enriched compared with the original minerals. The high-throughput sequencing analysis showed that S. thermosulfidooxidans were the predominant species during the early bioleaching period, and L. ferriphilum were the predominant species in the following period. A. caldus is consistently detected and accounts for 30–50% of the different growth stages. This study supplied a potentially practical application for the desulfurization in tin ore.
... Microorganisms can absorb, precipitate, oxidize, and reduce metals in the soil. For example, numerous mineral-oxidizing bacteria, commonly found in mines' sediments and soils, possess the ability to oxidize iron-and sulfur-containing minerals; such as sulfuroxidizing Acidithiobacillus thiooxidans, and Acidithiobacillus caldus, as well as iron-oxidizing bacteria like Acidithiobacillus ferrooxidans, Leptospirillum ferrooxidans and Leptospirillum ferriphilum (Clark and Norris, 1996;Leduc and Ferroni, 1994;Nagpal et al., 1993;Korehi et al.,2013;Vardanyan et al., 2023). Several fungal species have demonstrated potential for use in biomining like Penicillium simplicissimum and Aspergillus niger can effectively mobilize metals (Brauer, 1990;Mulligan et al., 2004;Shah et al., 2022). ...
The amount of mining waste containing metallic trace elements (MTE) is continuously rising because of the high demand for metals in industries, despite the significant risks that mining industries pose to the environment and public health, especially when the site is neglected without proper restoration measures after it has been closed. In this study, we conducted a review to provide a concise overview of the environmental and Human health issues caused by MTE originating from abandoned mining waste in Morocco. Additionally, we aimed to examine the solutions adopted or suggested in scientific research to solve these issues. To reach this, we utilized Scopus, Web of Science, PubMed, and regional databases, applying stringent inclusion and exclusion criteria to identify research publications from the past two decades. A detailed analysis of the studies revealed a correlation between the leaching of MTE from abandoned mine wastes and environmental problems such as the contamination of sediments, soils, waters, and crops. The predominant solutions suggested were biological methods, with a particular emphasis on phytoremediation and bioremediation, and physical and chemical treatment that often have limitations in terms of cost, efficiency, and potential negative impacts on the environment. In conclusion, bioremediation is an emerging and sustainable technology that harnesses microorganisms’ abilities to degrade or transform pollutants into less harmful forms. As environmental challenges increase, this approach offers a promising, eco-friendly solution for pollution management. Future efforts should focus on advancing research, optimizing microbial processes, and implementing pilot projects integrating bioremediation into broader environmental strategies to realize its full potential.
... The morphology of L. ferrooxidans is recognized for having a helically curved rod shape, it is a gram-negative iron-oxidizing bacterium, and it cannot oxidize sulfur compounds (Rojas-Chapana and Tributsch 2004). L. ferrooxidans is an acidophilic chemolithoautotrophic bacterium that can tolerate a pH of up to 1.2, moderately thermophilic with a growth temperature ranging from 20 to 45 °C, it oxidizes ferrous iron (Fe 2+ ) to ferric iron (Fe 3+ ) as a source of energy, the ferric ion attacks sulfide minerals in which metals of interest such as gold are occluded (Vardanyan et al. 2023). L. ferrooxidans can resist higher concentrations of uranium, molybdenum, and silver as compared to A. ferrooxidans, but it is more sensitive to copper and its growth rate is lower as compared to A. ferrooxidans; however, L. ferrooxidans can increase its growth by adding Zn 2+ (Kumar et al. 2019). ...
Biotechnology has increasing relevance worldwide in the mining sector, either as a response to the recovery of metals (gold, silver, copper, zinc, nickel, among others) as well as an alternative in the bioremediation of contaminated soil and water, frequent problems directly linked to mining activities. Hence, acidophilic microorganisms are of special scientific and industrial interest for the sustainable use of mineral resources. Nowadays, a wide variety of acidophilic chemolithotrophic microorganisms (MOs) are recognized, Acidithiobacillus ferrooxidans, Acidithiobacillus thiooxidans, Acidithiobacillus caldus, and Leptospirillum ferrooxidans, among others; those MOs grow in culture medium at pH ≤ 3 and obtain cellular energy from the oxidation of inorganic compounds, such as sulfur and iron. These microorganisms have different abilities to act on the mineral, converting insoluble metal sulfides into soluble metal sulfates of those species that are of interest, or that prevent optimal recovery of a specific mineral. Such microorganisms have been applied in biomining operations and are internationally known for the recovery of valuable metals from low-grade ores and refractory ores. Likewise, these acidophilic MOs can bioremediate soils contaminated with metals, extract metals from sludge generated as a byproduct in wastewater treatment, detoxify hazardous waste and recover metals from electronic waste; so the main interest of biomining processes lies in the economic impact that has benefited the world, since it is known that 5% of the gold and 20% of the copper that has been extracted worldwide are using this type of bacteria in bioleaching processes. The objective of this review is to expand the knowledge of the characteristics and applications of the main acidophilic microorganisms used in the solubilization/extraction of minerals, whether for the recovery of metals, bioremediation, or reduction of metals in different systems.
... These microbes are also known as iron and sulfur-oxidizing bacteria or acidophilic bacteria. They are involved in the oxidation of ferrous ion to ferric ion, or elemental sulfur to sulfuric acid during metal bioleaching ((Equations (1) and (2)) [33][34][35]. The biogenic ferric iron and sulfuric acid serve as oxidizing agents (lixiviants) for the mobilization of base metals from the solid matrix via acidolysis and redoxolysis bioleaching mechanisms (Equations (3)-(5)) [ ...
The rapid and improper disposal of electronic waste (e-waste) has become an issue of great concern, resulting in serious threats to the environment and public health. In addition, e-waste is heterogenous in nature, consisting of a variety of valuable metals in large quantities, hence the need for the development of a promising technology to ameliorate environmental hazards associated with the indiscriminate dumping of e-waste, and for the recovery of metal components present in waste materials, thus promoting e-waste management and reuse. Various physico-chemical techniques including hydrometallurgy and pyrometallurgy have been employed in the past for the mobilization of metals from e-waste. However, these approaches have proven to be inept due to high operational costs linked to the consumption of huge amounts of chemicals and energy, together with high metal loss and the release of secondary byproducts. An alternative method to avert the above-mentioned limitations is the adoption of microorganisms (bioleaching) as an efficient, cost-effective, eco-friendly, and sustainable technology for the solubilization of metals from e-waste. Metal recovery from e-waste is influenced by microbiological, physico-chemical, and mineralogical parameters. This review, therefore, provides insights into strategies or pathways used by microorganisms for the recovery of metals from e-waste.
In this study, Schwertmannite, Akaganéite and Ammoniojarosite were biosynthesized by different bacteria and characterized. Our results showed that bacteria are critical in mediating the mineral formation process: the morphology, crystallinity, grain size and specific surface area of each mineral varied upon different bacteria and culturing conditions. In addition, the formed minerals’ elemental composition and group disparity lead to different morphology, crystallinity and subsequent adsorption performance. In particular, adsorption difference existed in iron minerals biosynthesized by different bacteria. The maximal adsorption capacity of Akaganéite, Schwertmannite and Ammoniojarosite were 26.6 mg/g, 17.5 mg/g and 3.90 mg/g respectively. Our results also suggest that Cr(VI) adsorption on iron-minerals involves hydrogen bonding, electrostatic interaction, and ligand exchange. The adsorption only occurred on the surface of Ammoniojarosite, while for Akaganéite and Schwertmannite, the tunnel structure greatly facilitated the adsorption process and improved adsorption capacity. Thus, we conclude that the molecular structure is the primary determining factor for adsorption performance. Collectively, our results can provide useful information in selecting suitable bacteria for synthesizing heavy-metal scavenging minerals according to different environmental conditions.
The term ”thermophilic prokaryotes” covers an immense taxonomic and functional diversity of bacteria and archaea, spanning the length and breadth of the prokaryotic Tree of Life. Indeed, thermophiles are found within most major prokaryotic lineages and their functional diversity runs the gamut of biochemical and physiological adaptations. Thus, examples can be found of thermophilic lithoautotrophs as well as chemoheterotrophs, obligate anaerobes and aerophiles, extreme halophiles, acidophiles and alkaliphiles, and more. Their ecology is likewise diverse, with thermophiles found in a variety of habitats ranging from hydrothermal vents to desert soil to industrial settings and wastewater treatment facilities. It goes without saying that such immense diversity cannot be reviewed comprehensively in a relatively short book chapter. We thus aim to present examples pulled from diverse taxa within the vast menagerie of prokaryotic thermophiles in order to give insights into the metabolic, taxonomic, and ecological diversity of thermophilic prokaryotes rather than attempting an exhaustive review.
