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Experimental and bioinformatic approaches for analyzing and visualizing cyanobacterial nitrogen and hydrogen metabolism Röbbe Wünschiers*# Rikard Axelsson Martin Vellguth Peter Lindblad *Corresponding author Financial support: This work is part of the BMBF-funded Cologne University Bioinformatics Center (CUBIC) and was financially supported by grants to PL from the Swedish Research Council, the Swedish Energy Agency, and the EU/NEST Project SOLAR-H (contract 516510). Keywords: bioinformatics, cyanobacteria, DNA-microarrays, gene expression, metabolic pathways, nitrogen availability, nitrogen fixation. Present address: #SunGene GmbH & Co KGaA, Correnstrasse 3, 06466 Gatersleben, Germany.
Many cyanobacteria are capable of utilizing light energy for nitrogen fixation. As a by-product of this nitrogenase mediated catalysis, hydrogen gas is produced. Several approaches to increase hydrogen production from cyanobacteria exist. Usually, these approaches are non-targeted. Here we exemplify how DNA-microarray based gene-expression analysis and bioinformatic visualization techniques can be used to analyze nitrogen and hydrogen metabolism from the filamentous, heterocyst forming cyanobacterium Nostoc PCC 7120. We analyzed the expression of 1249 genes from major metabolic categories under nitrogen fixing and non-nitrogen fixing growth. Of the selected genes, 494 show a more than 2-fold expression difference in the two conditions analyzed. Under nitrogen-fixing conditions 465 genes, mainly involved in energy metabolism, photosynthesis, respiration and nitrogen-fixation, were found to be stronger expressed, whereas only 29 genes showed a stronger expression under non-nitrogen fixing conditions. To help understanding probe hybridization, all expression data were correlated with potential target secondary structures and probe GC-content. For the first time the expression of high light-induced stress proteins (HLIP-family) is shown to be linked to the nitrogen availability. |
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