Microbial Chromate Reduction Coupled to Anaerobic Oxidation of Elemental Sulfur or Zerovalent Iron

Abstract

Chromate (Cr­(VI)), as one of ubiquitous contaminants in groundwater, has posed a major threat to public health and ecological environment. Although various electron donors (e.g., organic carbon, hydrogen, and methane) have been proposed to drive chromate removal from contaminated water, little is known for microbial chromate reduction coupled to elemental sulfur (S(0)) or zerovalent iron (Fe(0)) oxidation. This study demonstrated chromate could be biologically reduced by using S(0) or Fe(0) as inorganic electron donor. After 60-day cultivation, the sludge achieved a high Cr­(VI) removal efficiency of 92.9 ± 1.1% and 98.1 ± 1.2% in two independent systems with S(0) or Fe(0) as the sole electron donor, respectively. The deposited Cr­(III) was identified as the main reduction product based on X-ray photoelectron spectroscopy. High-throughput 16S rRNA gene sequencing indicated that Cr­(VI) reduction coupled to S(0) or Fe(0) oxidation was mediated synergically by a microbial consortia. In such the consortia, S(0)- or Fe(0)-oxidizing bacteria (e.g., Thiobacillus or Ferrovibrio) could generate volatile fatty acids as metabolites, which were further utilized by chromate-reducing bacteria (e.g., Geobacter or Desulfovibrio) to reduce chromate. Our findings advance our understanding on microbial chromate reduction supported by solid electron donors and also offer a promising process for groundwater remediation.

Disentangling Microbial Syntrophic Mechanisms for Hexavalent Chromium Reduction in Autotrophic Biosystems

“…1a), and no sul te and thiosulfate were detected in the solution, suggesting that S 0 oxidation to sulfate may be directly coupled with Cr(VI) reduction. In the Fe-bioreactor, aqueous Fe (II) and Fe(III) were not detected, likely due to the formation of Fe-bearing minerals at circum-neutral pH condition ( Figure S2b) [10,14], suggesting that Cr(VI) reduction may be coupled with Fe 0 oxidation. The XPS analysis showed these precipitates had two typical peaks assigned to Fe 2p1/2 (725.0 − 727 eV) and…”

“…Each setting was amended with 5 g S 0 or Fe 0 as potential electron donors for Cr(VI) reduction. A previously described 200 mL synthetic groundwater was used as a medium [10,14] or Fe 0 oxidation by oxygen at room temperature (22 ± 2 °C). Long-term incubation was conducted in all bioreactors by feeding synthetic groundwater with Cr(VI) at multiple cycles (each for 120 h), and replenishing the medium until achieving a steady-state condition in ~ 160 days.…”

Insights into interactions between vanadium (V) bio-reduction and pentachlorophenol dechlorination in synthetic groundwater

“…Obtained sequences were submitted to the NCBI Sequence Read Archive with accession number SRP132559. RDP Classifier against silva (SSU115) 16S rRNA database was used to obtain the phylogenetic affiliations of representative sequences, following existing studies [8,36,37].…”

Insight into the nitrogen accumulation in urban center river from functional genes and bacterial community

“…The summer FCS community had the greatest abundance of statistically unique taxa. Most of the marker taxa in summer FCS, such as Smithella, Syntrophus, Thermomonas, Syntrophorhabdus, Thiobacillus, Christensenellaceae, and Rhodobacter (Fig 6C), could degrade diverse organic matters to acetate [34,35]. In the spring LHS, a large portion of organic degraders and heterotrophic denitrifiers were identified as the marker phylotype, including Flavobacterium, Massilia, Arenimonas, Pseudomonas, and Lysobacter, while the summer LHS taxa were dominated by Dechloromonas, Geothermobacter, Oxyphotobacteria, Geobacter, Fluviicola, and Methylomonas (Fig 8).…”