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Physiological, proteomic, and whole-genome transcriptional responses of Nitrosomonas europaea to heavy metals (Zn²⁺,Cd²⁺, Cu²⁺, and Hg²⁺) and cyanide : identification of heavy metals and cyanide stress response genes

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dc.contributor.advisor Ely, Roger
dc.creator Park, Sunhwa
dc.date.accessioned 2008-05-15T15:53:31Z
dc.date.available 2008-05-15T15:53:31Z
dc.date.copyright 2008-05-01
dc.date.issued 2008-05-15T15:53:31Z
dc.identifier.uri http://hdl.handle.net/1957/8494
dc.description Graduation date: 2008 en_US
dc.description.abstract Nitrosomonas europaea (ATCC19718) participates in the biological removal of nitrogen from wastewater by oxidizing ammonia to nitrite, the first step in nitrification. This bacterium is sensitive to heavy metals (Zn²⁺, Cd²⁺, Cu²⁺, and Hg²⁺) and cyanide, compounds commonly encountered in wastewater treatment plants. Therefore, we characterized physiological and transcriptional responses of N. europaea cells exposed to these inhibitors in batch reactors to identify stress-induced genes. N. europaea exposed to 3.4 uM ZnCl₂ showed about 61% inhibition in nitrification within 30 minutes. In microarrays of N. europaea exposed to 3.4 uM ZnCl₂ for 60 minutes, 27 genes were observed to be up regulated more than 2-fold, of the total of 2460 genes, while 30 genes were seen to be down regulated. Up-regulated genes included mercury resistance genes (merTPCAD), inorganic ion transport genes, oxidative stress genes, toxin-antitoxin genes (TA). merTPCAD was the highest up regulated operon (46-fold). Down- regulated genes included RubisCO (cbbO), biosynthesis (mrsA), and amino acid transporters. N. europaea exposed to 1 uM CdCl₂, 6 uM HgCl₂, or 8 uM CuCl₂ showed about 90% inhibition in nitrification within 30 minutes. In microarrays of N. europaea exposed to 1 uM CdCl₂ for 60 minutes, 66 genes were up regulated while 50 genes were down-regulated. merTPCADE showed the highest up regulation (277-fold) under cadmium stress. Interestingly, merA also showed 250-fold up regulation in N. europaea cells exposed to 6 uM HgCl₂. Therefore, merTPCADE appear to be common stress response genes to zinc, cadmium, and mercury exposure. N. europaea cells were very sensitive to low concentrations of cyanide; nitrification decreased about 50% in 30 minutes after exposure to 1 uM NaCN. In microarrays of N. europaea exposed to 1 uM NaCN for 60 minutes, 35 genes showed up regulation while 29 genes showed down regulation. A gene cluster that included moeZ (NE2353), encoding a rhodanese homologue, thought to be involved in detoxification of cyanide, showed the highest up regulation (7-fold). The down-regulated genes included genes encoding proteins involved in the sulfate reduction pathway, signal transduction mechanism, carbohydrate transport, energy production, and coenzyme metabolism. en_US
dc.language.iso en_US en_US
dc.subject Nitrosomonas europaea en_US
dc.subject Proteomic response en_US
dc.subject Transcriptional response en_US
dc.subject Heavy metal en_US
dc.subject Cyanide en_US
dc.subject Microarray en_US
dc.subject Bioengineering en_US
dc.subject Environmental engineering en_US
dc.subject.lcsh Bacteria, Nitrifying en_US
dc.subject.lcsh Heavy metals -- Physiological effect en_US
dc.subject.lcsh Cyanides -- Physiological effect en_US
dc.subject.lcsh Bacterial genetics en_US
dc.subject.lcsh Stress (Physiology) en_US
dc.title Physiological, proteomic, and whole-genome transcriptional responses of Nitrosomonas europaea to heavy metals (Zn²⁺,Cd²⁺, Cu²⁺, and Hg²⁺) and cyanide : identification of heavy metals and cyanide stress response genes en_US
dc.type Thesis en_US
dc.degree.name Doctor of Philosophy (Ph. D.) in Biological and Ecological Engineering en_US
dc.degree.level Doctoral en_US
dc.degree.discipline Engineering en_US
dc.degree.grantor Oregon State University en_US
dc.contributor.committeemember Chaplen, Frank
dc.contributor.committeemember Liu, Hong
dc.contributor.committeemember Plant, Thomas
dc.contributor.committeemember Dolan, Mark


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