Jiannan Ding

Molecular diversity of 16S rRNA and gyrB genes in copper mines

The molecular diversities of the microbial communities from four sites impacted by acid mine drainage (AMD) at Dexing Copper Mine in Jiangxi province of China were studied using 16S rRNA sequences and gyrB sequences. Of the four sampled sites, each habitat exhibited distinct geochemical characteristics and the sites were linked geographically allowing us to correlate microbial community structure to geochemical characteristics. In the present study, we examined the molecular diversity of 16S rRNA and gyrB genes from water at these sites using a PCR-based cloning approach. We found that the microbial community appears to be composed primarily of Proteobacteria, Acidobacteria, Actinobacteria, Nitrospira, Firmicutes, Chlorella and unknown phylotypes. Of clones affiliated with Nitrospira, Leptospirillum ferrooxidans, Leptospirillum ferriphilum and Leptospirillum group III were all detected. Principal-component analysis (PCA) revealed that the distribution of the microbial communities was influenced greatly by geochemical characteristics. The overall PCA profiles showed that the sites with similar geochemical characteristics had more similar microbial community structures. Moreover, our results also indicated that gyrB sequence analysis may be very useful for differentiating very closely related species in the study of microbial communities.

Growth and surface properties of new thermoacidophilic Archaea strain Acidianus manzaensis YN-25 grown on different substrates

Abstract The growth and surface properties of new thermoacidophilic Archaea strain Acidianus manzaensis YN-25 isolated from an acid hot spring in Tengchong, Yunnan Province, China were investigated cultured on different substrates including soluble substrate ferrous sulfate and nonsoluble solid substrates S 0 , pyrite and chalcopyrite. The growth characteristics of the cells in each substrate were characterized with the changes in cell number, pH, E h , and concentrations of Fe 2+ or SO 4 2− , or ratios of [Fe 2+ ] to [Fe 3+ ], and the surface properties were characterized and analyzed in terms of Zeta-potential, hydrophobicity, and surface FT-IR spectra of the cells. The results show that the cells grown on solid substrates have higher value of isoelectric points. They are more hydrophobic and express more surface proteins than ferrous sulfate grown cells.

Jarosite-type precipitates mediated by YN22, Sulfobacillus thermosulfidooxidans, and their influences on strain

Abstract To have a better understanding on the properties of the jarosite-type precipitate synthesized by Sulfobacillus thermosulfidooxidans, the evolution of the S. thermosulfidooxidans-mediated precipitation and the influence of the precipitate on this species, a newly isolated strain (YN22) of S. thermosulfidooxidans was cultured in a medium containing Fe2+ as energy source under optimal conditions (pH 1.5, 53 °C, 0.2 g/L yeast extract, 30 g/L Fe2SO4 · 7H2O and 170 r/min), added with or without glass beads. Remarkable differences were found in the oxidation rate of Fe2+, the precipitate yield of jarosite-type compounds and the population density between the two groups of cultures. The group with glass beads has a 6 h faster Fe2+ oxidation, 6 h earlier precipitation, 78% higher precipitate yield and much lower population density than those without glass beads. XRD, EDS, FTIR and SEM analysis reveals that the precipitates originated from both groups are a mixture of potassium jarosite and ammoniojarosite, with morphological features similar to the latter. The results of the test referring to influence of the precipitates on YN22 show that the precipitate from the group without glass beads has no apparent influence on Fe2+ oxidation rate of YN22 and only a limited influence on growth of the strain, whereas that from the group with glass beads remarkably inhibits the growth and Fe2+ oxidation ability of YN22 when a precipitate content over 4 g/L is used.

A novel acidophilic, thermophilic iron and sulfur-oxidizing archaeon isolated from a hot spring of tengchong, yunnan, China

A novel thermoacidophilic iron and sulfur-oxidizing archaeon, strain YN25, was isolated from an in situ enriched acid hot spring sample collected in Yunnan, China. Cells were irregular cocci, about 0.9-1.02 µm×1.0-1.31 µm in the medium containing elemental sulfur and 1.5-2.22 µm×1.8-2.54 µm in ferrous sulfate medium. The ranges of growth and pH were 50-85 (optimum 65) and pH 1.0-6.0 (optimum 1.5-2.5). The acidophile was able to grow heterotrophically on several organic substrates, including various monosaccharides, alcohols and amino acids, though the growth on single substrate required yeast extract as growth factor. Growth occurred under aerobic conditions or via anaerobic respiration using elemental sulfur as terminal electron acceptor. Results of morphology, physiology, fatty acid analysis and analysis based on 16S rRNA gene sequence indicated that the strain YN25 should be grouped in the species Acidianus manzaensis. Bioleaching experiments indicated that this strain had excellent leaching capacity, with a copper yielding ratio up to 79.16% in 24 d. The type strain YN25 was deposited in China Center for Type Culture Collection (=CCTCCZNDX0050).

Mutagenic breeding of silver-resistant Acidithiobacillus ferrooxidans and exploration of resistant mechanism

Abstract The silver-resistant Acidithiobacillus ferrooxidans were isolated from 22 acid mine drainage (AMD) samples collected from Dexing Copper Mine and Chengmen Mountain Mine, Jiangxi Province, China. Isolate DX16 is obtained from the sample taken from Dexing Copper Mine and still carries out ferrous ion oxidation when incubated in 9K medium containing silver nitrate (240 mg/L). While isolate HI, a less resistant strain taken from Yin Mountain Mine, has a tolerate level of only 60 mg/L. Based on 16S ribosomal DNA sequencing, both bacterial 16SrDNA sequences are 100% similar to Acidithiobacillus ferrooxidans ATCC 23270. Through ultraviolet irradiation induced mutations, isolate mDX16 that is obtained from DX16 carries out ferrous ion oxidation when incubated in 9K medium containing higher concentration of silver nitrate (250 mg/L). When silver-resistant gene ( SilC ) analysis is carried out on the two isolates, it is seen that this gene was absent in both.

Bioleaching of chalcopyrite with Acidianus manzaensis YN25 under contact and non-contact conditions

Abstract In order to investigate the contributions of contact and non-contact cells of Acidianus manzaensis ( A. manzaensis ) YN25 to the bioleaching of chalcopyrite, three experiments were carried out in the modified shake flasks. The redox potential, pH, cell density, copper and iron ions in the solution were monitored, and the morphological feature and chemical composition of the leached residues were analyzed. The highest leaching efficiency of Cu and Fe was reached in the experiment where the A. manzaensis YN25 could contact the surface of the chalcopyrite. There was no precipitation of jarosite in the leached residues of three experiments, but there was elemental sulfur in the leached residues when the cells could not contact the chalcopyrite. From these results, it is apparent that the leaching of the chalcopyrite is the cooperative action of the contact and non-contact A. manzaensis YN25.