Dataset Information

Specific mechanism of Acidithiobacillus caldus extracellular polymeric substances in the bioleaching of copper-bearing sulfide ore.

ABSTRACT: This study aimed to reveal the specific mechanism of extracellular polymeric substances (EPS) in the bioleaching of copper-bearing sulfide ore by moderately thermophilic bacterium Acidithiobacillus caldus. The bioleaching performance of blank control (BC), planktonic cell deficient (PD), attached cell deficient (AD), and EPS deficient (ED) systems were compared, to investigate the specific functions of "non-contact" and "contact" (including direct contact and, EPS-mediated contact) mechanisms. The detailed mechanics of bioleaching were studied using ?x of cell growth, scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR). The ?x of cell growth demonstrated that EPS favors planktonic and attached cell growth. SEM observation revealed that intensive micro-pores on slag benefitted from the "EPS-mediated contact" mechanism. XRD identification indicated that additional chemical derivatives were produced via "EPS-mediated contact" mechanism, because of the active iron/sulfur metabolism. FTIR analysis revealed that the absorption peaks of C-O-S, sulfate, and S = O, which are closely associated with sulfur metabolism, have significant influences of EPS secretion. Taken together, the "EPS-mediated contact" mechanism contributed to almost half of the "contact" mechanism efficiency and a quarter of the total bioleaching efficiency. The proposed specific mechanism of EPS can deepen our understanding of similar bioleaching processes.

SUBMITTER: Feng S

PROVIDER: S-EPMC6461249 | biostudies-literature | 2019

REPOSITORIES: biostudies-literature

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Specific mechanism of Acidithiobacillus caldus extracellular polymeric substances in the bioleaching of copper-bearing sulfide ore.

Feng Shoushuai S Li Kaijun K Huang Zhuangzhuang Z Tong Yanjun Y Yang Hailin H

PloS one 20190412 4

This study aimed to reveal the specific mechanism of extracellular polymeric substances (EPS) in the bioleaching of copper-bearing sulfide ore by moderately thermophilic bacterium Acidithiobacillus caldus. The bioleaching performance of blank control (BC), planktonic cell deficient (PD), attached cell deficient (AD), and EPS deficient (ED) systems were compared, to investigate the specific functions of "non-contact" and "contact" (including direct contact and, EPS-mediated contact) mechanisms. T ...[more]

PMID: 30978195

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Project description:The copper-sensitive operon repressor (CsoR) family, which is the main Cu(I)-sensing family, is widely distributed and regulates regulons involved in detoxification in response to extreme copper stress (a general range of ≥3 g/liter copper ions). Here, we identified CsoR in hyper-copper-resistant Acidithiobacillus caldus (CsoRAc), an organism used in the bioleaching process of copper ores. CsoRAc possesses highly conserved Cu(I) ligands and structures within the CsoR family members. Transcriptional analysis assays indicated that the promoter (PIII) of csoR was active but weakly responsive to copper in Escherichia coli. Copper titration assays gave a stoichiometry of 0.8 mol Cu(I) per apo-CsoRAc monomer in vitro combined with atomic absorption spectroscopy analysis. CuI-CsoRAc and apo-CsoRAc share essentially identical secondary structures and assembly states, as demonstrated by circular dichroism spectra and size exclusion chromatography profiles. The average dissociation constants (KD = 2.26 × 10-18 M and 0.53 × 10-15 M) and Cu(I) binding affinity of apo-CsoRAc were estimated by bathocuproine disulfonate (BCS) and bicinchoninic acid (BCA) competition assays, respectively. Site-directed mutations of conserved Cu(I) ligands in CsoRAc did not significantly alter the secondary structure or assembly state. Competition assays showed that mutants had the same order of magnitude of Cu(I) binding affinity as apo-CsoRAc. Moreover, apo-CsoRAc could bind to the DNA fragment P08430 in vitro, although with low affinity. Finally, a working model was developed to illustrate putative copper resistance mechanisms in A. caldus. IMPORTANCE Research on copper resistance among various species has attracted considerable interest. However, due to the lack of effective and reproducible genetic tools, few studies regarding copper resistance have been reported for A. caldus. Here, we characterized a major Cu(I)-sensing family protein, CsoRAc, which binds Cu(I) with an attomolar affinity higher than that of the Cu(I)-specific chelator bathocuproine disulfonate. In particular, CsoR family proteins were identified only in A. caldus, rather than A. ferrooxidans and A. thiooxidans, which are both used for bioleaching. Meanwhile, A. caldus harbored more copper resistance determinants and a relatively full-scale regulatory system involved in copper homeostasis. These observations suggested that A. caldus may play an essential role in the application of engineered strains with higher copper resistance in the near future.

Project description:The introduction of Acidithiobacillus thiooxidans A01 strengthens the positive interactions between physiologically distinct microorganisms and enhances the bioleaching ability of the consortium. However, the effect of introducing an exogenous strain, A. thiooxidans A01 on the structure and function of the adsorbed and planktonic microbial consortia during bioleaching of low-grade copper sulfide remains unclear. In this study, A. thiooxidans A01 was introduced into an indigenous leaching microbial community on the 0th (group B), 24th (group C), and 36th day (group D). Results revealed that the copper leaching efficiency was highest in group D, in which the Cu2+ concentration in the solution reached 251.5 mg/L on day 48, which was 18.5% higher than that of the control (group A, no addition of A. thiooxidans A01). Restriction fragment length polymorphism (RFLP) analysis of the microbial community in group D revealed the presence of Leptospirillum ferriphilum, Acidithiobacillus ferrooxidans, Acidithiobacillus caldus, Sulfobacillus sp., Acidiphilium spp., and Acidithiobacillus albertensis before introduction of A. thiooxidans A01 on the 36th or 48th day; however, A. albertensis was absent on day 48 in group A. Further, the proportion of dominant A. caldus, L. ferriphilum, and A. ferrooxidans became altered. The results of real-time PCR in group D showed that A. thiooxidans A01 was primarily adsorbed on the surface of the ore, with the adsorption reaching the maxima on day 42; while the free A. thiooxidans A01 in solution grew slowly, reaching its maximum concentration on day 45. Compared with that in the control group, the abundance of both free and attached A. caldus and Sulfobacillus sp. decreased following the introduction of A. thiooxidans A01, while that of L ferriphilum, A. ferrooxidans, and Acidiphilium sp. increased. Functional gene arrays data indicated that the abundance of genes involved in sulfide and iron oxidation in L. ferriphilum and A. ferrooxidans, as well as that of the metal (loid) resistance genes of A. ferrooxidans, L. ferriphilum, and Acidiphilium sp. increased, while the abundance of genes involved in sulfur metabolism in A. caldus and Sulfolobus spp. decreased. Taken together, these results provide useful information for application of bioleaching of copper sulfide in industry.

Dataset Information

Specific mechanism of Acidithiobacillus caldus extracellular polymeric substances in the bioleaching of copper-bearing sulfide ore.

Publications

Specific mechanism of Acidithiobacillus caldus extracellular polymeric substances in the bioleaching of copper-bearing sulfide ore.

Similar Datasets

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