Efficient iron acquisition mechanisms are fundamental for microbial survival in the environment and for pathogen virulence within their hosts. M. robertsii produces two known iron-binding natural products: metachelins, which are used to scavenge extracellular iron, and ferricrocin, which is strictly intracellular. To study the contribution of siderophore-mediated iron uptake and storage to M. robertsii fitness, we generated null mutants for each siderophore synthase gene (mrsidD and mrsidC, respectively), as well as for the iron uptake transcriptional repressor mrsreA. All of these mutants showed impaired germination speed, differential sensitivity to hydrogen peroxide, and differential ability to overcome iron chelation on growth-limiting iron concentrations. RT-qPCR data supported regulation of mrsreA, mrsidC, and mrsidD by supplied iron in vitro and during growth within the insect host, Spodoptera exigua. We also observed strong upregulation of the insect iron-binding proteins, transferrins, during infection. Insect bioassays revealed that ferricrocin is required for full virulence against S. exigua; neither the loss of metachelin production nor the deletion of the transcription factor mrsreA significantly affected M. robertsii virulence
virulence, iron, Siderophore, metachelins, ferricrocin, GATA transcriptional repressor
NCBI PubMed ID: 26135511Publication DOI: 10.1016/j.fgb.2015.06.008Journal NLM ID: 9607601Publisher: Orlando, FL : Academic Press / Elsevier
Correspondence: Donzelli BGG
Institutions: School of Integrative Plant Science - Plant Pathology and Plant-Microbe Biology Section, Cornell University, Ithaca, USA, USDA ARS, Robert W. Holley Center for Agriculture and Health, Ithaca, USA
Methods: DNA techniques, biological assays, UV, extraction, RT-PCR, CC, cell growth, HPLC-MS, mutagenesis, HR-ESI-MS, Congo Red assay, ion chromatography
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