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Global transcriptional analysis of Cr(VI)-adapted cells of Klebsiella sp. AqSCr

ABSTRACT: Hexavalent chromium (Cr(VI)) is a highly toxic contaminant, some bacteria are able to transform it to less toxic and less soluble trivalent chromium (Cr(III)). Klebsiella sp. strain AqSCr, isolated from Cr(VI)-polluted groundwater, reduces Cr(VI) both aerobically and anaerobically, and resists up 35 mM of Cr(VI); Subculturing of AqSCr in the presence of Cr(VI) conduces to adaptation. In this study, we performed RNA-Seq of Cr(VI) adapted stage, finding 255 genes upregulated and 240 downregulated with respect to controls without Cr(VI). Genes differentially expressed are mostly associated with oxidative stress response, DNA repair and replication, sulfur starvation response, envelope-osmotic stress response, fatty acid metabolism, ribosomal subunits and energy metabolism. Among them, genes not previously associated with chromium resistance as cybB, encoding a putative superoxide oxidase, gltA2, encoding an alternative citrate synthase, and des, encoding a fatty acid desaturase were upregulated. The alternative sigma factors fecl, rpoE and rpoS were upredgulated in Cr(VI) adapted cells, then they participate in orchestate the Cr(VI)-resistance mechanisms in AqSCr strain

ORGANISM(S): Klebsiella sp. AqSCr

PROVIDER: GSE160968 | GEO | 2021/05/20

REPOSITORIES: GEO

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Project description:Significant occupational and environmental exposures to hexavalent chromium, a metal with broad toxicity potential in humans, have been reported. In order to understand the mechanisms of dermal toxicity induced by hexavalent chromium, global gene expression profiling of human dermal fibroblasts exposed to a toxic concentration of potassium dichromate was performed. Microarray analysis of the gene expression profile in the fibroblasts treated with potassium dichromate identified significant differential expression of approximately 1,200 transcripts compared with the control cells. Hierarchical cluster analysis of the gene expression profile demonstrated a clear separation of the treated cells from the control group of cells. Functional categorization of the differentially expressed genes identified the enrichment of genes involved in several cellular processes, including apoptosis and oxidative stress, in the fibroblasts exposed to hexavalent chromium. Induction of apoptosis and generation of hydroxyl radicals indicative of oxidative stress in the dermal fibroblasts in response to their exposure to hexavalent chromium were independently confirmed by TUNEL assay and electron spin resonance (ESR) analysis, respectively. The potassium dichromate-induced cytotoxicity, differential gene expression, apoptosis, and oxidative stress were significantly blocked by the addition of ferrous sulfate, an agent known for its ability to reduce hexavalent chromium to the insoluble and therefore impermeable trivalent form, to the cell culture medium. Taken together, our data provide insights into the potential mechanisms underlying the dermal toxicity of hexavalent chromium and suggest a definite role for apoptosis and oxidative stress in Cr(VI)-induced cytotoxicity in human dermal fibroblasts. 16 samples were analyzed in this experiment. Exponentially growing human dermal fibroblasts (3x105 cells) were cultured in T25 cell culture flasks. When the cells were approximately 70% confluent, hexavalent potassium dichromate (5µM) was added to the medium with or without 40µM ferrous sulfate. Following 16 hours of culturing at 37oC, total RNA was isolated for gene expression studies. Details of the samples are: Control 4 Samples: Cr(0)-1, Cr(0)-2, Cr(0)-3, Cr(0)-4 Cr 5 µM 4 Samples: Cr(5)-5, Cr(5)-6, Cr(5)-7, Cr(5)-8 FeSO4 40 µM 4 Samples: Fe(40)-9, Fe(40)-10, Fe(40)-11, Fe(40)-12 Cr 5 µM + FeSO4 40 µM 4 Samples: Cr(5)+Fe(40)-13,Cr(5)+Fe(40)-14, Cr(5)+Fe(40)-15, Cr(5)+Fe(40)-16

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Global transcriptional analysis of Cr(VI)-adapted cells of Klebsiella sp. AqSCr

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