Selective removal of transition metals from acidic mine waters by novel consortia of acidophilic sulfidogenic bacteria.
Bottom Line: Two continuous-flow bench-scale bioreactor systems populated by mixed communities of acidophilic sulfate-reducing bacteria were constructed and tested for their abilities to promote the selective precipitation of transition metals (as sulfides) present in synthetic mine waters, using glycerol as electron donor.Analysis of the microbial populations in the bioreactors showed that they changed with varying operational parameters, and novel acidophilic bacteria (including one sulfidogen) were isolated from the bioreactors.The modular units are versatile and robust, and involve minimum engineering complexity.
Affiliation: School of Biological Sciences, Bangor University, Bangor LL57 2UW, UK.Show MeSH
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Mentions: Bacterial 16S rRNA genes were routinely amplified from both bioreactors, and subjected to semi‐quantitative terminal restriction enzyme fragment length polymorphism (T‐RFLP) analysis to assess changes in microbial community structures with varying operating conditions. All attempts at amplifying archaeal 16S rRNA genes were unsuccessful (in contrast to positive controls), indicating that methanogenic prokaryotes were absent in both bioreactors. Results from T‐RFLP analysis (Fig. 6) show that bacterial populations in both bioreactors changed in response to varying operational parameters. In the case of bioreactor I, the dominant terminal restriction fragment (T‐RF) when the reactor was maintained at pH 3.6 corresponded to a novel Firmicute (coded IR2) isolated from this bioreactor (see below). The same T‐RF was present when the pH of bioreactor I was lowered to pH 2.4 and then to 2.2, but in smaller relative abundance (Fig. 6A). T‐RFs corresponding to sulfidogenic bacteria were 138 nt (which accounted for 54% of the total peak area at pH 2.4, but which was detected in a small proportion at pH 3.6 and not detected at lower pH values than 2.4) and 214 nt (which accounted for, at most, 6% of total peak area) in length (HaeIII digests). The 138 nt corresponded to a novel acidophilic SRB (CEB3) which was also isolated from bioreactor I (see below) while the 214 nt restriction fragment is common to both Desulfosporosinus M1 and ‘Desulfobacillus (Db.) acidavidus’. Other T‐RFs identified were 253 nt (corresponding to Acidithiobacillus ferrooxidans), and 231 nt, which was only founded when the reactor I was maintained at pH 3.6, and corresponded to a Gram‐positive Actinobacterium isolate (IR1) isolated from bioreactor II maintained at pH 4.0 (described below). The relative abundance of the T‐RF corresponding to At. ferrooxidans increased as the pH of bioreactor I was lowered, from 6% of total peak area at pH 3.6 to 20% at pH 2.2 (Fig. 6A).
Affiliation: School of Biological Sciences, Bangor University, Bangor LL57 2UW, UK.