Project description:A whole genome DNA microarray was used to undertake a global transcriptional analysis of nitrogen fixation and ammonium repression in Pseudomonas stutzeri A1501. The aim of this study was to identify the genes that are up-regulated under nitrogen fixation conditions and rapidly down-regulated as soon as 10 min after ammonia shock. The expression changed genes may be the candidate genes for the ammonia signal transmission or be involved in the nitrogen regulatory mechanism. First, P. stutzeri A1501 was treated with 0.1 mM ammonia and 0.5% Oxygen tension until the nitrogenase activity was detectable. Then the cells were sudden shifted from the nitrogen fixation conditions to the ammonia repression conditions by addition of 20 mM ammonia for 10min. Subsequently, the bacterium was collected and began the RNA extraction process. Thus, we compare the expression profilings in these two conditions in order to identify the candidate genes.
