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Global Molecular and Morphological Effects of 24-Hour Chromium(VI) Exposure on Shewanella oneidensis MR-1

Authors
  • Karuna Chourey
  • Melissa R. Thompson
  • Jennifer Morrell-Falvey
  • Nathan C. VerBerkmoes
  • Steven D. Brown
  • Manesh Shah
  • Jizhong Zhou
  • Mitchel Doktycz
  • Robert L. Hettich
  • Dorothea K. Thompson
Publisher
American Society for Microbiology
Publication Date
Sep 01, 2006
Source
PMC
Keywords
Disciplines
  • Biology
  • Ecology
  • Geography
License
Unknown

Abstract

The biological impact of 24-h (“chronic”) chromium(VI) [Cr(VI) or chromate] exposure on Shewanella oneidensis MR-1 was assessed by analyzing cellular morphology as well as genome-wide differential gene and protein expression profiles. Cells challenged aerobically with an initial chromate concentration of 0.3 mM in complex growth medium were compared to untreated control cells grown in the absence of chromate. At the 24-h time point at which cells were harvested for transcriptome and proteome analyses, no residual Cr(VI) was detected in the culture supernatant, thus suggesting the complete uptake and/or reduction of this metal by cells. In contrast to the untreated control cells, Cr(VI)-exposed cells formed apparently aseptate, nonmotile filaments that tended to aggregate. Transcriptome profiling and mass spectrometry-based proteomic characterization revealed that the principal molecular response to 24-h Cr(VI) exposure was the induction of prophage-related genes and their encoded products as well as a number of functionally undefined hypothetical genes that were located within the integrated phage regions of the MR-1 genome. In addition, genes with annotated functions in DNA metabolism, cell division, biosynthesis and degradation of the murein (peptidoglycan) sacculus, membrane response, and general environmental stress protection were upregulated, while genes encoding chemotaxis, motility, and transport/binding proteins were largely repressed under conditions of 24-h chromate treatment.

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