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Genome-Wide Transcriptional Responses of Nitrosomonas europaea to Zinc

ABSTRACT: Nitrosomonas europaea is a Gram-negative obligate chemolithoautotroph that derives energy for growth through oxidation of ammonia and participates in the process of nitrification in global nitrogen cycling. 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 uM ZnCl2 decreased about 61 % and 69 % within 30 minutes, respectively. Two proteins were notably up regulated in zinc treatment and the mRNA levels of their encoding genes started to increase by one hour 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 (merACDPT), inorganic ion transport genes, oxidative stress genes, toxin-antitoxin genes (TA) and two-component signal transduction systems genes. The merACDPT was the highest up regulated operon (46-fold). Down-regulated genes included the RuBisCO operon (cbbO), carbohydrate transporter (mrsA and mnxG) and amino acid transporter. Keywords: zinc, stress response, global transcription, mercury resistance genes, inorganic ion transport genes, oxidative stress genes

ORGANISM(S): Nitrosomonas europaea

PROVIDER: GSE7552 | GEO | 2007/10/24

SECONDARY ACCESSION(S): PRJNA100367

REPOSITORIES: GEO

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Project description:Investigation of the whole genome gene expression level changes relative to exponential phase growth in Nitrosomonas europaea ATCC19718 after 12 hours ammonia starvation, 144 hours ammonia starvation, and 20 minutes following ammonia addition to starved cells. The ammonia monooxygenase of chemolithotrophic ammonia oxidizing bacteria (AOB) catalyzes the first step in ammonia oxidation by converting ammonia to hydroxylamine. The monooxygenase of Nitrosomonas europaea is encoded by two nearly identical operon copies (amoCAB1,2). Several AOB, including N. europaea, also posess a divergent monocistronic copy of amoC (amoC3) of unknown function. Previous work suggested a possible functional role for amoC3 in N. europaea during recovery from extended ammonia starvation as part of the σE- stress response regulon during the recovery of N. europaea from extended ammonia starvation, thus indicating its importance during the exit of cells from starvation. We here used global transcription analysis to show that expression of amoC3 is part of a general post-starvation cellular response system in N. europaea. We also found that amoC3 is required for efficient exit from prolonged ammonia starvation, as deleting this gene impaired growth at elevated temperatures and recovery following starvation under high oxygen tensions. Deletion of the σ32 global stress response regulator demonstrated that the heat shock regulon also plays a significant role in mediating the recovery of N. europaea from starvation. These findings provide the first described phenotype associated with the divergent AmoC3 subunit which appears to function as a stress responsive subunit capable of maintaining ammonia oxidation activity under stress conditions. A twelve chip study using total RNA recovered from four timepoints for each of three biological replicates of wild-type cultures of Nitrosomonas europaea ATCC 19718. Total RNA was obtained from each biological culture replicate during exponential growth, following 12 hours ammonia starvation, 144 hours ammonia starvations, and 20 minutes following ammonia addition to starved cells.

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Genome-Wide Transcriptional Responses of Nitrosomonas europaea to Zinc

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