coelicolor (Yang et al., 2006). The specificity for dCMP incorporation into pORF102 leaves the possibility that either the
see more first or the second nucleotide of the 3′-end of pAL1 (… GCAGG-3′) may serve as a template for the deoxynucleotidylation reaction. In this study, we identified the gene product of pAL1.102 as a protein that is associated with both termini of the linear Arthrobacter plasmid pAL1. The proposed TP – at least when fused to MBP to ensure solubility – was not capable of specifically recognizing telomeric pAL1 DNA in vitro. However, in an in vitro deoxynucleotidylation assay, the pORF102 protein specifically incorporated dCMP, complementary to the 3′-ends of pAL1. This is consistent with its presumed role as a protein primer in DNA replication. The financial support of the Deutsche Forschungsgemeinschaft is gratefully acknowledged (FE 383/11). We thank Prof. Dr R. Brandsch (University of Freiburg, Germany) for kindly providing the vector pART2, and Prof. Dr A. Steinbüchel (Münster) for access to the phosphoimager. We also thank Manuel Tomm for initial EMSA experiments, and Gabriele Niester and Almut Kappius for technical assistance. Table S1. Primers and ssDNA template
GSK J4 molecular weight used in this study. Please note: Wiley-Blackwell is not responsible for the content or functionality of any supporting materials supplied by the authors. Any queries (other than missing material) should be directed to the corresponding author for the article. “
“Many bacteria produce siderophores for sequestration of growth-essential iron. Analysis of the Salinispora genomes suggests that these
marine actinomycetes support multiple hydroxamate- and phenolate-type siderophore pathways. We isolated and characterized desferrioxamines (DFOs) B and E from all three recognized Salinispora species and linked their biosyntheses in S. tropica CNB-440 and S. arenicola CNS-205 to the des locus through PCR-directed mutagenesis. Gene inactivation of the predicted iron-chelator until biosynthetic loci sid2-4 did not abolish siderophore chemistry. Additionally, these pathways could not restore the native growth characteristics of the des mutants in iron-limited media, although differential iron-dependent regulation was observed for the yersiniabactin-like sid2 pathway. Consequently, this study indicates that DFOs are the primary siderophores in laboratory cultures of Salinispora. Siderophores are small molecules secreted by bacteria to sequester growth-essential ferric iron that is poorly soluble under neutral pH and aerobic conditions (Neilands, 1995). The structures of siderophores vary considerably and are often suited to the environmental niche of the producing bacterium. For example, amphiphilic siderophores possess hydrophobic fatty acid chains that enable them to remain associated with the cell membrane (Martinez et al., 2003) – an attribute particularly advantageous in pelagic marine environments where dilution occurs rapidly.