title: Caulobacter crescentus as a whole-cell uranium biosensor.
abstract: We engineered a strain of the bacterium Caulobacter crescentus to fluoresce in the presence of micromolar levels of uranium at ambient temperatures when it is exposed to a hand-held UV lamp. Previous microarray experiments revealed that several Caulobacter genes are significantly upregulated in response to uranium but not in response to other heavy metals. We designated one of these genes urcA (for uranium response in caulobacter). We constructed a reporter that utilizes the urcA promoter to produce a UV-excitable green fluorescent protein in the presence of the uranyl cation, a soluble form of uranium. This reporter is specific for uranium and has little cross specificity for nitrate (<400 microM), lead (<150 microM), cadmium (<48 microM), or chromium (<41.6 microM). The uranium reporter construct was effective for discriminating contaminated groundwater samples (4.2 microM uranium) from uncontaminated groundwater samples (<0.1 microM uranium) collected at the Oak Ridge Field Research Center. In contrast to other uranium detection methodologies, the Caulobacter reporter strain can provide on-demand usability in the field; it requires minimal sample processing and no equipment other than a hand-held UV lamp, and it may be sprayed directly on soil, groundwater, or industrial surfaces.
authors: Department of Developmental Biology, Beckman Center, Stanford University School of Medicine, Stanford, California 94305, USA.
authors: Nathan J
authors: NJ
authors: Hillson
authors: Ping
authors: P
authors: Hu
authors: Gary L
authors: GL
authors: Andersen
authors: Lucy
authors: L
authors: Shapiro
mesh_terms: D015374:Biosensing Techniques / Q000379:methods*; D002104:Cadmium / Q000494:pharmacology; D016935:Caulobacter crescentus / Q000187:drug effects / Q000235:genetics* / Q000528:radiation effects; D002857:Chromium / Q000494:pharmacology; D015964:Gene Expression Regulation, Bacterial / Q000187:drug effects / Q000235:genetics* / Q000528:radiation effects; D005798:Genes, Bacterial / Q000235:genetics; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D007854:Lead / Q000494:pharmacology; D009566:Nitrates / Q000494:pharmacology; D011401:Promoter Regions, Genetic / Q000235:genetics; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D014466:Ultraviolet Rays; D014501:Uranium / Q000032:analysis / Q000494:pharmacology*; D014875:Water Pollutants, Radioactive / Q000032:analysis / Q000494:pharmacology
chemical_list: D009566:Nitrates; D011993:Recombinant Fusion Proteins; D014875:Water Pollutants, Radioactive; D002104:Cadmium; D002857:Chromium; D049452:Green Fluorescent Proteins; D007854:Lead; D014501:Uranium