Ferritin and ferrihydrite nanoparticles as iron sources for Pseudomonas aeruginosa |
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Authors: | Carolyn Dehner Nydia Morales-Soto Rabindra K Behera Joshua Shrout Elizabeth C Theil Patricia A Maurice Jennifer L Dubois |
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Institution: | 1. Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN, 46556, USA 6. Biochemistry Program, Smith College, Northampton, MA, USA 3. Department of Civil and Environmental Engineering and Earth Sciences, University of Notre Dame, Notre Dame, IN, 46556, USA 4. Department of Biological Sciences, University of Notre Dame, Notre Dame, IN, 46556, USA 2. Children’s Hospital Oakland Research Institute, Oakland, 94609, USA 7. Department of Chemistry and Biochemistry, University of South Carolina, Columbia, SC, USA 5. Biosciences Division, Center for Infectious Diseases and Biodefense Research, SRI International, 140 Research Drive, Harrisonburg, VA, 22802, USA
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Abstract: | Metabolism of iron derived from insoluble and/or scarce sources is essential for pathogenic and environmental microbes. The ability of Pseudomonas aeruginosa to acquire iron from exogenous ferritin was assessed; ferritin is an iron-concentrating and antioxidant protein complex composed of a catalytic protein and caged ferrihydrite nanomineral synthesized from Fe(II) and O2 or H2O2. Ferritin and free ferrihydrite supported growth of P. aeruginosa with indistinguishable kinetics and final culture densities. The P. aeruginosa PAO1 mutant (ΔpvdDΔpchEF), which is incapable of siderophore production, grew as well as the wild type when ferritin was the iron source. Such data suggest that P. aeruginosa can acquire iron by siderophore-independent mechanisms, including secretion of small-molecule reductant(s). Protease inhibitors abolished the growth of the siderophore-free strain on ferritins, with only a small effect on growth of the wild type; predictably, protease inhibitors had no effect on growth with free ferrihydrite as the iron source. Proteolytic activity was higher with the siderophore-free strain, suggesting that the role of proteases in the degradation of ferritin is particularly important for iron acquisition in the absence of siderophores. The combined results demonstrate the importance of both free ferrihydrite, a natural environmental form of iron and a model for an insoluble form of partly denatured ferritin called hemosiderin, and caged ferritin iron minerals as bacterial iron sources. Ferritin is also revealed as a growth promoter of opportunistic, pathogenic bacteria such a P. aeruginosa in diseased tissues such as the cystic fibrotic lung, where ferritin concentrations are abnormally high. |
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