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Microarray was used to study the gene expression of P. stutzeri A1501 under different growth conditions

ABSTRACT: Nitrogen fixation is a highly energy-demanding process and highly regulated at multiple levels. The two major signals that regulate nitrogen fixation in most diazotrophs are oxygen and ammonia. In order to study the complex regulated mechanism and to highlight the complete nitrogen fixing system in genome level, here we present the transcriptional profiles of the nitrogen fixation genes of P.stutzeri A1501 in different growth conditions with a genome-wide DNA microarray. In this study, the three samples of "P.stutzeri A1501 treated with 0.1mM ammonia and 0.5% Oxygen tension","P.stutzeri A1501 treated with 0.1mM ammonia and 0.5% Oxygen tension-2" and "P.stutzeri A1501 treated with 0.1mM ammonia and 0.5% Oxygen tension-3" were three repeat experiments, while, the other three samples of "P.stutzeri A1501 treated with 20mM ammonia and 0.5% Oxygen tension-1", "P.stutzeri A1501 treated with 20mM ammonia and 0.5% Oxygen tension-2" and "P.stutzeri A1501 treated with 20mM ammonia and 0.5% Oxygen tension-3" were three repeat experiments. The gene expressions under these two growth phases were compared to investigate which genes' expression were effected by different ammonia concentrations. Keywords: nitrogen fixation, nitrogen repression

ORGANISM(S): Stutzerimonas stutzeri A1501

PROVIDER: GSE6572 | GEO | 2007/04/20

SECONDARY ACCESSION(S): PRJNA98751

REPOSITORIES: GEO

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Project description:Nitrogen fixation is a highly energy-demanding process and highly regulated at multiple levels. The two major signals that regulate nitrogen fixation in most diazotrophs are oxygen and ammonia. In order to study the complex regulated mechanism and to highlight the complete nitrogen fixing system in genome level, here we present the transcriptional profiles of the nitrogen fixation genes of P.stutzeri A1501 in different growth conditions with a genome-wide DNA microarray. In this study, the three samples of "P.stutzeri A1501 treated with 0.1mM ammonia and 0.5% Oxygen tension","P.stutzeri A1501 treated with 0.1mM ammonia and 0.5% Oxygen tension-2" and "P.stutzeri A1501 treated with 0.1mM ammonia and 0.5% Oxygen tension-3" were three repeat experiments, while, the other three samples of "P.stutzeri A1501 treated with 20mM ammonia and 0.5% Oxygen tension-1", "P.stutzeri A1501 treated with 20mM ammonia and 0.5% Oxygen tension-2" and "P.stutzeri A1501 treated with 20mM ammonia and 0.5% Oxygen tension-3" were three repeat experiments. The gene expressions under these two growth phases were compared to investigate which genes' expression were effected by different ammonia concentrations. Keywords: nitrogen fixation, nitrogen repression P.stutzeri whole genome microarray, which was based on our sequenced strain A1501. The microarray used in this study featured 3988 of the 4145 ORFs identified in P.stutzeri strain A1501, because 157 ORFs were not on the microarray of the inability to amplify these products. ORFs were amplified with specific primer pairs (Invitrogen). To ensure that the elements of our array would detect specifically their corresponding genes and no others, the ORF coordinates fed into the primer program were circumscribed such that they would exclude regions of any ORF that contained significant similarity to any other ORF. Agarose gel electrophoresis was used to perform quality control on all PCR products. Oligonucleotides were removed from the PCR mix by PCR 96 cleanup plate (Millipore). DNA was resuspended in 12 Î¼l of spotting solution containing 50% dimethyl sulfoxide. PCR products were spotted onto gamma amino propylsilan coated GAPII slides (Corning) with a OmniGrid â¢ microarrayer (GeneMachines).The negative control genes were from the type III secretion system genes of shigella flexneri 2a and the commercial Arabidopsis genes (SpotReportâ¢ cDNA Array Validation System, Stratagene). The positive control genes were from the 16S rRNA of P.stutzeri A1501. We used Cy3-labeled genomic DNA and Cy5 dye-labeled cDNA, for hybridization. The cDNA was synthesized by reverse transcription of 5 Î¼g of total RNA. The labeled cDNA and genomic DNA samples were mixed and hybridized at 65â for 16 hours. Genomic DNA was used as a universal internal control for the quality of the microarray and also allowed for the comparison of results across multiple experiments. Each experiment was repeated three times from the beginning of inoculation.

Project description:Biological nitrogen fixation, the microbial reduction of atmospheric nitrogen to bioavailable ammonia, represents both a major limitation on biological productivity and a highly desirable engineering target for synthetic biology. However, the engineering of nitrogen fixation requires an integrated understanding of how the gene regulatory dynamics of host diazotrophs respond across sequence-function space of its central catalytic metalloenzyme, nitrogenase. Here, we interrogate this relationship by analyzing the transcriptome of Azotobacter vinelandii engineered with a phylogenetically inferred ancestral nitrogenase protein variant. The engineered strain exhibits reduced cellular nitrogenase activity but recovers wild-type growth rates following an extended lag period. We find that expression of genes within the immediate nitrogen fixation network is resilient to the introduced nitrogenase sequence-level perturbations. Rather the sustained physiological compatibility with the ancestral nitrogenase variant is accompanied by reduced expression of genes that support trace metal and electron resource allocation to nitrogenase. Our results spotlight gene expression changes in cellular processes adjacent to nitrogen fixation as productive engineering considerations to improve compatibility between remodeled nitrogenase proteins and engineered host diazotrophs. IMPORTANCE Azotobacter vinelandii is a key model bacterium for the study of biological nitrogen fixation, an important metabolic process catalyzed by nitrogenase enzymes. Here, we demonstrate that compatibilities between engineered A. vinelandii strains and nitrogenase variants can be modulated at the regulatory level. The engineered strain studied here responds by adjusting the expression of proteins involved in cellular processes adjacent to nitrogen fixation, rather than that of nitrogenase proteins themselves. These insights can inform future strategies to transfer nitrogenase variants to non-native hosts.

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Microarray was used to study the gene expression of P. stutzeri A1501 under different growth conditions

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