Background: Several studies have demonstrated the formation of Fe-As co-precipitation products in waters rich in As and metals. Further studies applying this process to water technology have shown the potential for Fe-As co-precipitation in the removal of As from groundwater storage tanks. Formation of iron oxides and Fe-As co-precipitates occur spontaneously abiotically but, at low oxygen concentrations, the reaction rates of As(III) and Fe(II) oxidation are increased by bacterial processes with respect to chemical reactions alone, resulting in stabilisation of co-precipitates and scavenging of Fe and As. However, under more reduced conditions, anaerobic Bacteria and Archaea may induce their release. Objective: To investigate the prokaryotic community and biogeochemistry in a Fe-As coprecipitate from a groundwater storage tank in Bangladesh over a 5-year period, particularly with regard to population structure changes, and to infer biogeochemical mechanisms that may contribute to the formation and stability of co-precipitates and Fe-As redox cycling. Methods: Prokaryotic diversity within the co-precipitate was assessed micro-morphologically by SEM, and genetically by bacterial and archaeal 16S rRNA gene PCR-DGGE of co-precipitate DNA sampled during 2005-2009. In addition, PCR-cloning of bacterial 16S rRNA genes were undertaken on samples from 2008. Conclusions: Results suggested that Fe-As co-precipitates provide a habitat for a phylogenetically and metabolically diverse group of prokaryotes, dominated by Gallionella-like iron-oxidisers and methylotrophic bacteria, as well as methanogens, sulphate-reducers and other novel prokaryotic lineages. Interestingly, no phylotypes known to be involved in As cycling were detected.
Diversity of Prokaryotes Inhabiting Natural Iron-Arsenic Co-precipitation Products from Groundwater
GORRA, ROBERTA;MARTIN, Maria;
2011-01-01
Abstract
Background: Several studies have demonstrated the formation of Fe-As co-precipitation products in waters rich in As and metals. Further studies applying this process to water technology have shown the potential for Fe-As co-precipitation in the removal of As from groundwater storage tanks. Formation of iron oxides and Fe-As co-precipitates occur spontaneously abiotically but, at low oxygen concentrations, the reaction rates of As(III) and Fe(II) oxidation are increased by bacterial processes with respect to chemical reactions alone, resulting in stabilisation of co-precipitates and scavenging of Fe and As. However, under more reduced conditions, anaerobic Bacteria and Archaea may induce their release. Objective: To investigate the prokaryotic community and biogeochemistry in a Fe-As coprecipitate from a groundwater storage tank in Bangladesh over a 5-year period, particularly with regard to population structure changes, and to infer biogeochemical mechanisms that may contribute to the formation and stability of co-precipitates and Fe-As redox cycling. Methods: Prokaryotic diversity within the co-precipitate was assessed micro-morphologically by SEM, and genetically by bacterial and archaeal 16S rRNA gene PCR-DGGE of co-precipitate DNA sampled during 2005-2009. In addition, PCR-cloning of bacterial 16S rRNA genes were undertaken on samples from 2008. Conclusions: Results suggested that Fe-As co-precipitates provide a habitat for a phylogenetically and metabolically diverse group of prokaryotes, dominated by Gallionella-like iron-oxidisers and methylotrophic bacteria, as well as methanogens, sulphate-reducers and other novel prokaryotic lineages. Interestingly, no phylotypes known to be involved in As cycling were detected.
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