Project description:Iron is limiting in the environment, bacteria respond to this deprivation by activating genes required for bacterial iron homeostasis. Transcriptional regulation in response to iron in Gram-negative bacteria is largely mediated by the ferric uptake regulator protein Fur, which in the presence of iron binds to a specific sequence in the promoter regions of genes under its control and acts as a repressor. Here we describe comparative global gene expression analysis using DNA microarray based on the whole genome sequence of the magnetotactic bacterium Magnetospirillum magneticum AMB-1 was conducted between wild type strain and a non-magnetic NMA61 mutant strain, generated by mini-Tn5 transposon mutagenesis which is incapable of assimilating iron to cytoplasm. No induction of the fur genes in NMA61 mutant strain was considered to be due to low intracellular iron concentration. In the iron-replete condition, among 4492 genes, 434 genes were down-regulated and 527 genes were up-regulated in the wild type strain. Among 434 genes down-regulated, 299 genes were not down-regulated in NMA61 mutant strain, indicating these genes are candidates of Fur-regulated. Keywords: Iron, magnetotactic bacteria
Project description:Iron is limiting in the environment, bacteria respond to this deprivation by activating genes required for bacterial iron homeostasis. Transcriptional regulation in response to iron in Gram-negative bacteria is largely mediated by the ferric uptake regulator protein Fur, which in the presence of iron binds to a specific sequence in the promoter regions of genes under its control and acts as a repressor. Here we describe comparative global gene expression analysis using DNA microarray based on the whole genome sequence of the magnetotactic bacterium Magnetospirillum magneticum AMB-1 was conducted between wild type strain and a non-magnetic NMA61 mutant strain, generated by mini-Tn5 transposon mutagenesis which is incapable of assimilating iron to cytoplasm. No induction of the fur genes in NMA61 mutant strain was considered to be due to low intracellular iron concentration. In the iron-replete condition, among 4492 genes, 434 genes were down-regulated and 527 genes were up-regulated in the wild type strain. Among 434 genes down-regulated, 299 genes were not down-regulated in NMA61 mutant strain, indicating these genes are candidates of Fur-regulated. A non-magnetic mutant of Magnetospirillum magneticum AMB-1 (NMA61) generated transposon mutagenesis was grown under various iron conditions. Global gene expression analysis of iron-inducible genes was conducted by using DNA microarray.
Project description:Investigation of whole genome expression changes in Magnetospririllum magneticum mutants, probing the role of the CtrA regulatory pathway. The mutants are further described in a manuscript submitted for publication at J. Bacteriology. Developmental events across the prokaryotic life cycle are highly regulated at the transcriptional and post-translational levels. Key elements of a few regulatory networks are conserved among phylogenetic groups of bacteria, although the features controlled by these conserved systems are as diverse as the organisms encoding them. In this work, we probe the role of the CtrA regulatory network, conserved throughout the Alphaproteobacteria, in the magnetotactic bacterium, Magnetospirillum magneticum strain AMB-1, which possesses unique intracellular organization and compartmentalization. While we show that CtrA in AMB-1 is not essential for viability, it is required for motility, and its putative phosphorylation state dictates the ability of CtrA to activate the flagella biosynthesis gene cascade. Gene expression analysis of strains expressing active and inactive CtrA alleles point to the composition of the extended CtrA regulon, including both direct and indirect targets. These results, combined with a bioinformatic study of the AMB-1 genome, enabled the prediction of an AMB-1 specific CtrA binding site. Further, phylogenetic studies comparing CtrA sequences from Alphaproteobacteria in which the role of CtrA has been experimentally examined reveals an ancestral role of CtrA in the regulation of motility and suggests that its essential functions in other Alphaproteobacteria were acquired subsequently.
Project description:Expression analysis of Magnetospirillum magneticum AMB-1 WT, ΔMAI, ΔctrA, ΔdivK, and ΔctrA complemented with CtrA D51E, CtrA D51A, and an empty vector control
