Characterization of the Bradyrhizobium japonicum NtrC regulon by DNA Microarray analysis.. Bradyrhizobium diazoefficiens USDA 110

The Bradyrhizobium japonicum NtrC regulatory protein influences gene expression in response to changes in intracellular nitrogen status. Under conditions of low nitrogen, phosphorylation of NtrC results in up-regulation of a number of genes involved in nitrogen metabolism and nitrogen acquisition. To better define the exact nature of NtrC’s influence on gene expression, a ntrC mutation was created in B. japonicum and transcriptional profiling was performed by DNA microarray analysis of both the mutant and wild type strains. Overall design: Bradyrhizobium japonicum USDA 110 and a ntrC mutant in the USDA 110 background were cultured in minimal medium supplemented with either 10mM glutamate (low nitrogen) or 10mM ammonium and 10mM glutamate (high nitrogen) as nitrogen sources. Four comparisons were performed: wild type high nitrogen vs. mutant high nitrogen, wild type low nitrogen vs. wild type high nitrogen, wild type low nitrogen vs. mutant low nitrogen, and mutant low nitrogen vs. mutant high nitrogen. For each of the four comparisons, three biological replicates were prepared for each strain and dye swap replications were performed for each hybridization producing a total of six arrays per comparison and 24 arrays in total.