Academic literature on the topic 'Acidophiles'

Although reduced inorganic sulfur compound (RISC) oxidation in many chemolithoautotrophic sulfur oxidizers has been investigated in recent years, there is little information about RISC oxidation in heterotrophic acidophiles. In this study,Acidicaldussp. strain DX-1, a heterotrophic sulfur-oxidizing acidophile, was isolated. Its genome was sequenced and then used for comparative genomics. Furthermore, real-time quantitative PCR was performed to identify the expression of genes involved in the RISC oxidation. Gene encoding thiosulfate: quinone oxidoreductase was present inAcidicaldussp. strain DX-1, while no candidate genes with significant similarity to tetrathionate hydrolase were found. Additionally, there were genes encoding heterodisulfide reductase complex, which was proposed to play a crucial role in oxidizing cytoplasmic sulfur. Like many heterotrophic sulfur oxidizers,Acidicaldussp. strain DX-1 had no genes encoding enzymes essential for the direct oxidation of sulfite. An indirect oxidation of sulfite via adenosine-5′-phosphosulfate was proposed inAcidicaldusstrain DX-1. However, compared to other closely related bacteriaAcidiphilium cryptumandAcidiphilium multivorum, which harbored the genes encoding Sox system, almost all of these genes were not detected inAcidicaldussp. strain DX-1. This study might provide some references for the future study of RISC oxidation in heterotrophic sulfur-oxidizing acidophiles.

Acidophiles have been widely used in heap and dump bioleaching of secondary copper sulfide ores and biooxidation of refractory gold ores. 22 genera of acidophiles have been found in biomining environments. This paper gives a preliminary introduction to the application of mineral biomining in China. Challenges and technical trends for heap bioleaching of primary copper sulfide ores, purification of bioleaching solution of polymetallic sulfide ores and biooxidation of carbonaceous refractory gold ores are also recommended.

ABSTRACT Glycolic acid was detected as an exudate in actively growing cultures of three chemolithotrophic acidophiles that are important in biomining operations, Leptospirillum ferriphilum, Acidithiobacillus (At.) ferrooxidans, and At. caldus. Although similar concentrations of glycolic acid were found in all cases, the concentrations corresponded to ca. 24% of the total dissolved organic carbon (DOC) in cultures of L. ferriphilum but only ca. 5% of the total DOC in cultures of the two Acidithiobacillus spp. Rapid acidification (to pH 1.0) of the culture medium of At. caldus resulted in a large increase in the level of DOC, although the concentration of glycolic acid did not change in proportion. The archaeon Ferroplasma acidiphilum grew in the cell-free spent medium of At. caldus; glycolic acid was not metabolized, although other unidentified compounds in the DOC pool were metabolized. Glycolic acid exhibited levels of toxicity with 21 strains of acidophiles screened similar to those of acetic acid. The most sensitive species were chemolithotrophs (L. ferriphilum and At. ferrivorans), while the most tolerant species were chemoorganotrophs (Acidocella, Acidobacterium, and Ferroplasma species), and the ability to metabolize glycolic acid appeared to be restricted (among acidophiles) to Firmicutes (chiefly Sulfobacillus spp.). Results of this study help explain why Sulfobacillus spp. rather than other acidophiles are the main organic carbon-degrading bacteria in continuously fed stirred tanks used to bioprocess sulfide mineral concentrates and also why temporary cessation of pH control in these systems, resulting in rapid acidification, often results in a plume of the archaeon Ferroplasma.