title: Global molecular and morphological effects of 24-hour chromium(VI) exposure on Shewanella oneidensis MR-1.
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.
authors.affiliation: Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA.
authors.forename: Karuna
authors.initials: K
authors.lastname: Chourey
authors.forename: Melissa R
authors.initials: MR
authors.lastname: Thompson
authors.forename: Jennifer
authors.initials: J
authors.lastname: Morrell-Falvey
authors.forename: Nathan C
authors.initials: NC
authors.lastname: Verberkmoes
authors.forename: Steven D
authors.initials: SD
authors.lastname: Brown
authors.forename: Manesh
authors.initials: M
authors.lastname: Shah
authors.forename: Jizhong
authors.initials: J
authors.lastname: Zhou
authors.forename: Mitchel
authors.initials: M
authors.lastname: Doktycz
authors.forename: Robert L
authors.initials: RL
authors.lastname: Hettich
authors.forename: Dorothea K
authors.initials: DK
authors.lastname: Thompson
mesh_terms: D001426:Bacterial Proteins / Q000096:biosynthesis / Q000235:genetics; D001483:Base Sequence; D002473:Cell Wall / Q000378:metabolism; D002840:Chromates / Q000494:pharmacology; D002857:Chromium / Q000494:pharmacology*; D004269:DNA, Bacterial / Q000235:genetics / Q000378:metabolism; D004734:Energy Metabolism; D004785:Environmental Pollutants / Q000494:pharmacology; D015870:Gene Expression / Q000187:drug effects; D005798:Genes, Bacterial; D005810:Multigene Family; D039002:Prophages / Q000235:genetics; D020543:Proteome; D020592:Shewanella / Q000187:drug effects* / Q000235:genetics / Q000254:growth & development / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D002840:Chromates; D004269:DNA, Bacterial; D004785:Environmental Pollutants; D020543:Proteome; D002857:Chromium