Project description:Magnetosomes are complex membrane organelles synthesized by magnetotactic bacteria (MTB) for navigation in the magnetic field. Their formation is tightly controlled by ˃30 specific magnetosome genes arranged in operons. The transcriptional organization of these operons in the model MTB Magnetospirillum gryphiswaldense MSR-1 has been long viewed to be simple, having each a convenient promoter that enable transcription of the operon as a single transcriptional unit. Here, by applying Cappable-seq and whole transcriptome shotgun RNA sequencing, we revealed multiple additional transcription starting sites (TSS) within the magnetosome operons mamABop, mms6op and mamXYop. Using experimental validation by bioluminescence reporter, we demonstrated that most of the new TSS are generated by biologically meaningful promoters. Furthermore, the knockout of the primary promoters in mamABop and mms6op resulted only in mild impairments of the magnetosome formation, suggesting that additional transcripts are indeed generated within these operons. Besides, we identified a strong promoter in the intergenic region within mamXYop, which transcript likely represents a non-coding RNA important for proper expression of the genes in this operon. The promoter sequences from MSR-1 are conservative in most magnetotactic Magnetospirillum spp., but not in other MTB, suggesting the functional conservation in magnetospirilla but independent evolution of the transcription circuits within the magnetosome operons in different phylogenetic groups. Taken together, our data suggest much more complex transcriptional architecture of the magnetosome operons in MSR-1 than deemed before and contribute to unraveling the fundamentals of magnetosome biosynthesis at transcriptional level.

2021-08-20 | GSE168986 | GEO

Identification of Iron-Inducible Genes in Magnetospirillum magneticum AMB-1 Non-Magnetic Mutant

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.

2010-07-01 | E-GEOD-5832 | biostudies-arrayexpress

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