Cr(VI) Reduction by Sulfidogenic and Nonsulfidogenic Microbial Consortia

Arias, Y. Meriah; Tebo, Bradley M.

doi:10.1128/aem.69.3.1847-1853.2003

Cited by 62 publications

(32 citation statements)

References 33 publications

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“…Most were similar to characterized Cr(VI)-resistant strains that have been found in Cr-polluted soils (5,20) and microcosms from marine sediments (3,4). Several of the sequences obtained in this microcosm experiment are similar (94 to 100%) to sequences of dominant DGGE bands obtained by community analysis of soils from the same location (13).…”

Section: Discussionsupporting

confidence: 55%

Responses of the Anaerobic Bacterial Community to Addition of Organic C in Chromium(VI)- and Iron(III)-Amended Microcosms

Kourtev¹,

Nakatsu

Konopka³

2006

Appl Environ Microbiol

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Chromium (VI) is toxic to microorganisms and can inhibit the biodegradation of organic pollutants in contaminated soils. We used microcosms amended with either glucose or protein (to drive bacterial community change) and Fe(III) (to stimulate iron-reducing bacteria) to study the effect of various concentrations of Cr(VI) on anaerobic bacterial communities. Microcosms were destructively sampled based on microbial activity (measured as evolution of CO 2 ) and analyzed for the following: (i) dominant bacterial community by PCRdenaturing gradient gel electrophoresis (DGGE) of the 16S rRNA gene; (ii) culturable Cr-resistant bacteria; and (iii) enrichment of iron-reducing bacteria of the Geobacteraceae family by real-time PCR. The addition of organic C stimulated the activities of anaerobic communities. Cr(VI) amendment resulted in lower rates of CO 2 production in glucose microcosms and a slow mineralization phase in protein-amended microcosms. Glucose and protein amendments selected for different bacterial communities. This selection was modified by the addition of Cr(VI), since some DGGE bands were intensified and new bands appeared in Cr(VI)-amended microcosms. A second dose of Cr(VI), added after the onset of activity, had a strong inhibitory effect when higher levels of Cr were added, indicating that the developing Cr-resistant communities had a relatively low tolerance threshold. Most of the isolated Cr-resistant bacteria were closely related to previously studied Cr-resistant anaerobes, such as Pantoea, Pseudomonas, and Enterobacter species. Geobacteraceae were not enriched during the incubation. The studied Cr(VI)-contaminated soil contained a viable anaerobic bacterial community; however, Cr(VI) altered its composition, which could affect the soil biodegradation potential.

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Section: Discussionsupporting

confidence: 55%

Responses of the Anaerobic Bacterial Community to Addition of Organic C in Chromium(VI)- and Iron(III)-Amended Microcosms

Kourtev¹,

Nakatsu

Konopka³

2006

Appl Environ Microbiol

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“…In contrast, iron-reducing bacteria such as Shewanella spp. may be important for the enzymatic and/or chemical reduction of Cr(VI) as representatives of that genus were found in enrichment cultures from Cr(VI)-contaminated sites (2). Little is known about the effect of Cr(VI) or Cr(III) on the survival of these bacteria.…”

Section: Introductionmentioning

confidence: 99%

“…In addition, Cr(VI) is reduced chemically by hydrogen sulfide or ferrous iron which are end products of sulfate or iron reduction respectively. However, recent studies (2,3) have documented that SRB are sensitive to Cr(VI) and, consequently, their role in Cr(VI) reduction is limited. In contrast, iron-reducing bacteria such as Shewanella spp.…”

Section: Introductionmentioning

confidence: 99%

Toxicity of Cr(III) to Shewanella sp. Strain MR-4 during Cr(VI) Reduction

Bencheikh-Latmani

Obraztsova

Mackey

et al. 2006

Environ. Sci. Technol.

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109

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Bioremediation of chromium through the reduction of hexavalent chromium (as the chromate ion, CrO4 2-) is based on the notion that the product, trivalent chromium (Cr(III)), is less toxic than chromate. In this study, we show that soluble Cr(III), present at pH 6−8 as the Cr3+ ion and/or hydroxyl complexes (henceforth referred to as uncomplexed Cr(III)), can be found transiently in significant concentrations and has a deleterious effect on Shewanella sp. MR-4. However, Cr(III) complexed to an organic ligand or precipitated as Cr(OH)3(s) has little or no effect on cells. Similarly, during the reduction of Cr(VI) by strain MR-4, complexation of the product, Cr(III), results in increased cell survival and extended Cr(VI) reduction activity. These results and gene expression data obtained by qRT−PCR (quantitative reverse transcription−PCR) suggest that the observed toxic effect of Cr(III) formed during Cr(VI) reduction or added as an uncomplexed species is due to the interference with basic cell activities such as DNA transcription and/or replication. Important implications for the bioremediation of Cr(VI)-contaminated sites emerge from this study: Cr(VI) reduction by Shewanella sp. MR-4 is enhanced and sustained by the presence of compounds able to complex Cr(III) as it is being formed but, in turn, the complexation of Cr(III) precludes its precipitation and immobilization.

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“…Under oxygen-limited conditions, chromium(VI) can be reduced (biologically or chemically) to insoluble and relatively nontoxic Cr(III) (22). Despite the potential interactions between biotic and chemical components, the responses of anaerobic microbial activities to Cr(VI) have not been well studied (6,7,42,43).…”

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confidence: 99%

Inhibition of Nitrate Reduction by Chromium(VI) in Anaerobic Soil Microcosms

Kourtev

Nakatsu

Konopka

2009

Appl Environ Microbiol

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Chromium is often found as a cocontaminant at sites polluted with organic compounds. For nitrate-respiring microbes, Cr(VI) may be not only directly toxic but may also specifically interfere with N reduction. In soil microcosms amended with organic electron donors, Cr(VI), and nitrate, bacteria oxidized added carbon, but relatively low doses of Cr(VI) caused a lag and then lower rates of CO 2 accumulation. Cr(VI) strongly inhibited nitrate reduction; it occurred only after soluble Cr(VI) could not be detected. However, Cr(VI) additions did not eliminate Cr-sensitive populations; after a second dose of Cr(VI), bacterial activity was strongly inhibited. Differences in microbial community composition (assayed by PCR-denaturing gradient gel electrophoresis) driven by different organic substrates (glucose and protein) were smaller than when other electron acceptors had been used. However, the selection of bacterial phylotypes was modified by Cr(VI). Nine isolated clades of facultatively anaerobic Cr(VI)-resistant bacteria were closely related to cultivated members of the phylum Actinobacteria or Firmicutes. In Bacillus cereus GNCR-4, the nature of the electron donor (fermentable or nonfermentable) affected Cr(VI) resistance level and anaerobic nitrate metabolism. Our results indicate that carbon utilization and nitrate reduction in these soils were contingent upon the reduction of added Cr(VI). The amount of Cr(VI) required to inhibit nitrate reduction was 10-fold less than for aerobic catabolism of the same organic substrate. We speculate that the resistance level of a microbial process is directly related to the diversity of microbes capable of conducting it.

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Cr(VI) Reduction by Sulfidogenic and Nonsulfidogenic Microbial Consortia

Cited by 62 publications

References 33 publications

Responses of the Anaerobic Bacterial Community to Addition of Organic C in Chromium(VI)- and Iron(III)-Amended Microcosms

Responses of the Anaerobic Bacterial Community to Addition of Organic C in Chromium(VI)- and Iron(III)-Amended Microcosms

Toxicity of Cr(III) to Shewanella sp. Strain MR-4 during Cr(VI) Reduction

Inhibition of Nitrate Reduction by Chromium(VI) in Anaerobic Soil Microcosms

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