Bacterial populations in samples of bioleached copper ore as revealed by analysis of DNA obtained before and after cultivation

Abstract

The composition of bacterial populations in copper bioleaching systems was investigated by analysis of DNA obtained either directly from ores or leaching solutions or after laboratory cultures. This analysis consisted of the characterization of the spacer regions between the 16 and 23S genes in the bacterial rRNA genetic loci after PCR amplification. The sizes of the spacer regions, amplified from DNAs obtained from samples, were compared with the sizes of those obtained from cultures of the main bacterial species isolated from bioleaching systems. This allowed a preliminary assessment of the bacterial species present in the samples. Identification of the bacteria was achieved by partial sequencing of the 16S rRNA genes adjacent to the spacer regions. The spacer regions observed in DNA from columns leached at different iron concentrations indicated the presence of a mixture of different bacteria. The spacer region corresponding to Thiobacillus ferrooxidans was the main product observed at high ferrous iron concentration. At low ferrous iron concentration, spacer regions of different lengths, corresponding to Thiobacillus thiooxidans and ''Leptospirillum ferrooxidans'' were observed. However, T. ferrooxidans appeared to predominate after culture of these samples in medium containing ferrous iron as energy source. Although some of these strains contained singular spacer regions, they belonged within previously described groups of T. ferrooxidans according to the nucleotide sequence of the neighbor 16S rRNA. These results illustrate the bacterial diversity in bioleaching systems and the selective pressure generated by different growth conditions.

High‐rate ferric sulfate generation by a Leptospirillum ferriphilum‐dominated biofilm and the role of jarosite in biomass retainment in a fluidized‐bed reactor

“…This study confirms that the Leptospirillum sp. is clearly more dominant in bioleaching applications (Pizarro et al, 1996;Rawlings et al, 1999;Sand et al, 1992; this study) than previously estimated (for reviews, see Torma and Bosecker, 1982;Jensen and Webb, 1995). The high ferric/ferrous ratio, a low pH (Rawlings et al, 1999), and temperature above 20jC (Sand et al, 1992) have been suggested as the main reasons for the predominance of Leptospirillum sp.…”

Recovery of novel bacterial diversity from a forested wetland impacted by reject coal

“…We identified several novel sequence groups within our RCP samples not recovered in other AMD molecular studies (Goebel and Stackebrandt, 1994;Pizarro et al, 1996;Edwards et al, 1998;Bond et al, 2000a) that were related to acidophilic isolates (Table 2). RCP2-8 and RCP2-10 clustered with the alpha Proteobacteria, Acidisphaera rubrifaciens (a heterotrophic AMD isolate (Hiraishi et al, 2000) and Rhodophila globiformis [a anoxygenic phototroph that grows optimally at pH 4.5-5.5 (Pfennig, 1974)] along with environmental clones recovered from an acidic geothermal spring (Atkinson et al, 2000) and an acidic polychlorinated biphenyl-contaminated soil (Nogales et al, 2000).…”

“…A recent collection of 16S rDNA-based studies conducted within Iron Mountain, CA, an extreme AMD system (pH ∼ 0-1, temperature 30-50 ° C), revealed that the associated bacterial communities primarily represented uncultivated organisms phylogenetically related to described acidophilic bacteria (Bond and Banfield, 2001). Conversely, 16S rDNA surveys conducted in less extreme AMD systems (pH ∼ 2-3, temperature less than 30 ° C) have recovered bacterial sequence types that were generally identical to those commonly cultured from these same samples (Goebel and Stackebrandt, 1994;Pizarro et al ., 1996).…”

Detection by polmerase chain reaction-amplification and sequencing of an archaeon in a commercial-scale copper bioleaching plant

“…Agglomerated ore and leached, and cultures were prepared as described previously [10, 11]. Total DNA was extracted from ores and cultures as described previously [10, 11].…”