Genome-wide transcriptional responses of Nitrosomonas europaea to zinc
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Nitrosomonas europaea, a Gram-negative obligate chemolithoautotroph, participates in global nitrogen cycling by carrying out nitrification and derives energy for growth through oxidation of ammonia. In this work, the physiological, proteomic, and transcriptional responses of N. europaea to zinc stress were studied. The nitrite production rate and ammonia-dependent oxygen uptake rate of the cells exposed to 3.4 μM ZnCl2 decreased about 61 and 69% within 30 min, respectively. Two proteins were notably up regulated in zinc treatment and the mRNA levels of their encoding genes started to increase by 1 h after the addition of zinc. A total of 27 genes were up regulated and 30 genes were down regulated. Up-regulated genes included mercury resistance genes (merTPCAD), inorganic ion transport genes, oxidative stress genes, toxin-antitoxin genes, and two-component signal transduction systems genes. merTPCAD was the highest up-regulated operon (46-fold). Down-regulated genes included the RubisCO operon (cbbO), biosynthesis (mrsA), and amino acid transporter.
KeywordsNitrosomonas europaea 2-D SDS-PAGE Zinc cDNA microarray Quantitative reverse transcriptase-PCR
The research in this study was funded through NSF proposal number 0412711. We thank Daniel J. Arp, Luis A. Sayavedra-Soto, and Tyler S. Radniecki for critical reading of the manuscript, and Barbara O. Gvakharia for experimental advice and discussion. We also thank the Center for Genome Research and Biocomputing (CGRB) at Oregon State University for providing facilities for RNA quality and microarray experiments.
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