title: Population dynamics of a single-stage sulfidogenic bioreactor treating synthetic zinc-containing waste streams.
abstract: Waste streams from industrial processes such as metal smelting or mining contain high concentrations of sulfate and metals with low pH. Dissimilatory sulfate reduction carried out by sulfate-reducing bacteria (SRB) at low pH can combine sulfate reduction with metal-sulfide precipitation and thus open possibilities for selective metal recovery. This study investigates the microbial diversity and population changes of a single-stage sulfidogenic gas-lift bioreactor treating synthetic zinc-rich waste water at pH 5.5 by denaturing gradient gel electrophoresis of 16S rRNA gene fragments and quantitative polymerase chain reaction. The results indicate the presence of a diverse range of phylogenetic groups with the predominant microbial populations belonging to the Desulfovibrionaceae from delta-Proteobacteria. Desulfovibrio desulfuricans-like populations were the most abundant among the SRB during the three stable phases of varying sulfide and zinc concentrations and increased from 13% to 54% of the total bacterial populations over time. The second largest group was Desulfovibrio marrakechensis-like SRB that increased from 1% to about 10% with decreasing sulfide concentrations. Desulfovibrio aminophilus-like populations were the only SRB to decrease in numbers with decreasing sulfide concentrations. However, their population was <1% of the total bacterial population in the reactor at all analyzed time points. The number of dissimilatory sulfate reductase (DsrA) gene copies per number of SRB cells decreased from 3.5 to 2 DsrA copies when the sulfide concentration was reduced, suggesting that the cells' sulfate-reducing capacity was also lowered. This study has identified the species present in a single-stage sulfidogenic bioreactor treating zinc-rich wastewater at low pH and provides insights into the microbial ecology of this biotechnological process.
authors.affiliation: Department of Molecular Biology, Umeå University, Umeå 90187, Sweden.
authors.forename: Shabir A
authors.initials: SA
authors.lastname: Dar
authors.forename: Martijn F M
authors.initials: MF
authors.lastname: Bijmans
authors.forename: Inez J T
authors.initials: IJ
authors.lastname: Dinkla
authors.forename: Bert
authors.initials: B
authors.lastname: Geurkink
authors.forename: Piet N L
authors.initials: PN
authors.lastname: Lens
authors.forename: Mark
authors.initials: M
authors.lastname: Dopson