Effects of iron-limitation ofEscherichia coli on growth,the respiratory chains and gallium uptake |
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Authors: | Julia A. M. Hubbard Krystyna B. Lewandowska Martin N. Hughes Robert K. Poole |
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Affiliation: | (1) Department of Chemistry, King's College London, Kensington Campus, Campden Hill Road, W8 7AH London, UK;(2) Department of Microbiology, King's College London, Kensington Campus, Campden Hill Road, W8 7AH London, UK;(3) Present address: Centre for Biotechnology, Imperial College of Science and Technology, South Kensington, SW7 2AZ London, UK;(4) Present address: School of Chemistry, Kingston Polytechnic, Penrhyn Road, Kingston-upon-Thames, Surrey, UK |
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Abstract: | The effects of iron limitation on growth, the composition and function of the respiratory chains, and gallium uptake inEscherichia coli have been studied. Decreasing the iron concentration in a defined medium using Chelex resin gave lower growth yields in both continuous culture and prolonged batch culture. In the former, ironlimited (entering [Fe]2.0 M) cells exhibited diminished respiration rates, respiration-driven proton translocation quotients, and levels of non-haem iron and cytochromes. The cellular concentration of haemoproteinb-590 (a cytochromea1-like hydroperoxidase) decreased 20-fold on iron limitation, whilst a CO-binding pigment with an absorption maximum in the dithionite-treated form near 500 nm appeared. Gallium(III) (9 M) added to iron-limited, but not iron-sufficient, cultures diminished growth yields further; cells grown with low entering concentrations of iron took up less gallium than iron-sufficient cells. These results are attributed to the interference by gallium(III) with siderophore-mediated metal uptake. Gallium also stimulated iron uptake and was itself accumulated by iron-sufficient cells, suggesting that gallium(III) also affects the iron transport system(s) of low affinity. |
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Keywords: | Iron-limitation Escherichia coli Respiratory chains Cytochromes Gallium Metal uptake |
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